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Hey everybody what's going on this is Caleb with Deb's Lopes dot com.

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And in this video I'm going to show you how we can use our ax swift to transmit and send values back

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and forth between View controllers just like you might with a Segway or even with protocols.

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It's really really cool and actually super easy in our X-Wing.

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So let's go ahead and let's pull open our project and let's get started.

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So we're first going to create a new view controller and a button on our current view controller right

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here.

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So let's begin actually by creating that view controller.

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Drag it on just like that looks good.

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And let's set a background color for this visi.

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I like this blue color which if you want to use it you can.

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It's 4 7 8 C6.

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Feel free to use that.

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And what we're going to do next is we're going to go ahead and copy and paste these into this view controller

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like so.

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And you know while I'm at it I'm going to put him in a stacked view.

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I'm going to go ahead and pin it one hundred twenty from the top 20 from the left 20 from the right.

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And let's give it a height of 120 then let's give it some spacing of 20.

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And that looks good.

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So you know what that's green.

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Let's change this to be blue.

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You don't have to.

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Just bothers me that it's not the same.

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So anyway that's great.

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Now let's go ahead and let's add a button to this view controller let's put it down here below the stack

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view.

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And let's just go ahead and type a plus sign and add name that looks good.

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Let's stretch it out so it fits.

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Looks awesome.

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Let's change the font and color to custom Avenir next.

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You guys know that's my favorite.

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And how about Demy bold.

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That looks good.

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And let's make it a size 20.

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Let's change the font color to white and let's give it some constraints to stretch it out.

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So we're going to set it to be eight from the top and let's do I don't know how about 30 from the left

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30 from the right.

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There we go.

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Got a nice big button.

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Hard to miss.

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And now all we need to do is basically link up these to their appropriate controllers.

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But this blue Visi doesn't have a view controller yet so let's right click on our X namer click new

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file Cocco touch class and let's name this add name Visi K. press next.

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Add it to your project.

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And now we're going to go ahead and enter the storyboard again and set this identity or set the identity

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of this view controller.

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So select the VC select the identity inspector and change the class to add name visi.

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And while we're at it let's go ahead and set up the storyboard ideas well because that's what we're

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going to use to instantiate the view controller later.

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So copy this paste it into storyboard ID and press enter to lock it in place.

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Now let's go ahead and let's set up the appropriate Iby actions that we need.

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So click on the green view controller.

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Open up the assistant editor and make sure that you're on automatic and view controller.

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Now we probably could change this name here but I'm not going to.

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Just because.

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So let's go ahead and let's all right click and drag and create an IP outlet.

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Let's call it add name button.

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All right.

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And next let's go ahead and click on Add name visi.

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And it should switch over there we go.

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While we're here let's get rid of did receive memory warning and the commented code there we don't need

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this included get rid of that.

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Ok cool.

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And now let's go ahead and let's.

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Right click and drag from this text field and call this new name textfield and connect it then right

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click and drag from the button and call this submit button.

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Like so go ahead and get rid of that space.

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And now we're going to go ahead and set up our other view controller this green one here to present

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this blue view controller.

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So let's go ahead and let's head into view controller and we're going to create a new function called

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phunk bind.

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Add name button OK and this is what we're going to do to bind our ADD name button to our view controller.

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So go ahead and call add name button.

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OK that's the name of our X and since it's a button we can access dot tap k.

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So whenever tap is called that's what's going to happen.

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Now I want to make sure that I don't accidentally instantiate multiple copies of view of a controller.

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Let's say that I tap the button super fast and was somehow able to present four or five instances of

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a view controller that would not be good with Eric Swift we can call a function called Dot throttle.

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And what that's going.

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Oops only Tootsie's throttle and what throttle is going to let us do is it's basically going to prevent

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us from putting more input in than we want.

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So to call throttle we're going to go ahead and put some parentheses here and we can give it a due time

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and a schedule or not.

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I've already shown you this.

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It's similar to the bounce.

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But what it's going to do is it's basically going to ignore input that is duplicate within a certain

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time frame.

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So 0.5 seconds is plenty of time.

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That means if I push the button once it's going to lock it out and not pay attention to any other input

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until after point five seconds.

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Now the scheduler like I always like I showed you is main schedular instance.

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OK it's a singleton class so we need to call the instance at the end and main scheduler is basically

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just the main dispatch queue.

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It's just a handy way of using it.

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So now we are throttling our input so we don't accidentally instantiate too many of you controllers.

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And now what we can do is call subscribe and that's where we're going to basically call what would happen

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in an IB action.

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K whatever happens when the button is pressed so called don't subscribe subscribe.

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And on next is what we're going to call and inside of the next closure we're going to go ahead and create

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an instance of ADD baby seat.

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So go ahead and type guard let add name Visi equals storyboard instantiate controller with identifier.

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This is how we're going to use the View Controller to create an instance of a particular view controller.

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So go ahead and give some quotes there just single quotes and we're going to call it ad name the C because

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that's the idea that we just set.

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So very cool.

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It's yelling at us of course because we're a closure so we're going to go ahead and call self-taught

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storyboard because we're in a closure we need to keep a reference to self and the inside of a guard.

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We need to create an additional condition in case we can't instantiate this properly.

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So instead of crashing we're gonna go ahead and just call.

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Else.

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And if we can't properly instantiate that we're just going to go ahead and print could not create and

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name visi.

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All right.

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So that's what will happen if we can't instantiate it but we will be able to.

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So don't worry now that we have that initialization.

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Here's what we can do.

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We can create a publish subject do you member publish subjects.

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They basically allow us to subscribe and then put in elements and the subscription is going to pay attention

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to anything that is added after the subscription.

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So in order to actually do this we need to go into ad Daim Visi and create an instance of publish subject.

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So I'm going to go ahead and do that beneath these Iby outlets.

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I'm going to go ahead and call Let name subject and that's going to be equal to published subject.

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Although we have not yet imported the proper frameworks so go ahead and import our acts swift and import.

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Whoa.

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Hello.

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Import our cocoa.

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So now we should have access to publish subject.

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There it is now of course we're dealing with strings because we are dealing with you know text fields

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and labels so this is going to be a published subject of type string.

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And we're going to instantiate it from the beginning.

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So we're also going to need a Dispose bag because later we're going to subscribe to our submit button

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and we need to be able to deallocate the memory.

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So go ahead and call Let dispose bag equals dispose bag and instantiate it.

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Now we don't need to do anything just yet but we do need to be able to access this name subject because

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when we instantiate the view controller we're basically going to link this publish subject to our array

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and our other view controller.

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Whenever we push in a name from the other view controller it's going to go ahead and push in the new

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name with an on next call.

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So here's what we're going to do.

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We've created an instance of ADD named visi.

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Now it's yelling at us and let's figure out why it says guard body may not fall through.

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Consider using a return or throw.

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Oh that's right I sorry.

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So we need to return or break.

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And so what we can actually do is we can call fatal error and fatal error has a string property and

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basically fatal error is going to return and print an error message at the same time.

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OK that's a good way for error handling.

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So now what we're going to do in our view controller is we're going to go ahead and access our names

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subject.

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So now we need to do is access add named Visi like so and try to access our names subject.

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But we can't and you know why.

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Because we have not actually set up our instance of the controller here to be of type add named visi.

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Check it out.

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This just returns a view controller so we need to cast this optionally as ADD named visi.

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So now if I go in to add named Visi I can push Dot and I can get access to our name subject or I should

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be able to maybe I need to build.

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Let's try that again.

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There we go.

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OK.

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Now name subject is showing up so if you don't see it just build and that should solve that problem.

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So add named Visi that name subject.

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And here's what we're going to do.

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We're going to go ahead and subscribe to it.

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And then whenever a value is added into it we can append that to our array in this view controller.

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So go ahead and call subscribe and we're going to call on next.

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As you may have expected and whenever a value is passed into this name subject we're going to call self

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names array.

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OK remember that's our ray that is presenting all the names at the bottom of the view controller self

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name xray dot value k we need to access the array and we need to append something from this subject

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OK from our published subject.

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But we currently don't have a way to access whatever is returned in this closure.

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So to do that after the bracket go ahead and call name in OK we've just set up a property.

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So whatever value gets passed in at Next we can access it using this variable name.

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So we're going to pass in name.

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Okay that makes sense.

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Our array just got a new name.

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Now if this is confusing to you it's OK.

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We're going to see how it works and then you'll understand it'll click I promise.

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So it's giving me an error.

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That's because we have built it will go away.

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There we go.

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Very cool.

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So what we are doing here is we are setting up this view controller to be subscribing to the names subject

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in AD named visi.

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Then whenever we push something in this value is going to be added to our names array on the previous

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controller so we can subscribe on different view controllers it works that way it's very very cool.

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Then next after we push add we want to go ahead and call add name Visi dismiss.

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OK we want it to go away to show our view controller beneath it.

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So go ahead and call.

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True and completion will be nil.

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All right.

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Now it's literally that easy to pass in the values.

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But of course we need to call add to dispose bag.

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And so we'll do that like so.

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And look at that we are one step closer to actually passing values between the view controllers here.

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Now I'm just sort of doing some cleanup here to make it look nice.

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And now now that we have subscribed.

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Oh sorry we're inclosures we need to call self-taught dispose back.

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Now that we have successfully subscribed so that when we pass in values we're going to go ahead and

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present this view controller because we have our subscription all set up so go ahead and just call self

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that present.

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And for the view controller to present it's going to be at named Visi animated of course is true and

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the completion is nil.

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Basically what we're going to do is when we tap the button we're going to throttle the input by point

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five seconds.

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We create an instance of ADD named Visi and we set up the name subject to have a subscription on this

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green view controller so that whenever a value is passed in we append it to the array in the green view

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controller then we dismiss the controller.

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OK.

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But since that won't happen from the get go we added to the Dispose bag at the very end of course and

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then we actually present this instance.

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So basically this is like a function that is set up whenever we pass in a value to the name subject.

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But when the controller first presents there's no values we haven't tapped the button to push in a value

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yet.

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So we have now set it up to present the proper view controller and dismiss it when we're ready.

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Very very cool.

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So of course we need to call bind add name function to view did load.

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So go ahead and call that.

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There we go.

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Bind add named function and now the last thing we need to do is to set up our submit button on the blue

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view controller which if you remember looks like this.

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We're going to set up this button here so that when we push it we push in a value to our name subject

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and therefore add a value to the array and dismiss the blue view controller.

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So go ahead an inside add named visi.

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We're going to create a function down here called phunk bind submit button and here we go.

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Let's go ahead and set this up.

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So go ahead and call submit button.

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Our X-Com tap and we're going to subscribe to it meaning whenever we tap it we're going to do something.

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So go ahead and call subscribe on next.

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And in the brackets of the closure we're going to go ahead and call self name subject on next and we

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can pass in a value.

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Now where are we going to get that value.

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The textfield.

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So let's go ahead and let's do that self.

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Got any new name textfield text.

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And of course for some Rapide because it's from an optional string of textfield.

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And that's it.

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We push the button.

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The subscription happens.

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We pass in the value from the textfield the value gets added to the array.

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The view controller gets dismissed and it will show up on the previous view controller we're talking

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between New controllers thinks to subjects.

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Very very cool.

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Now I just realized there could be an issue.

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We will basically be able to pass in blank names.

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We don't want that so we can say if self dot new name textfield text is not equal to an empty string

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whoops we can go ahead and call on next.

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So that'll prevent us from actually passing in a blank value.

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But you know what guys we are really really close.

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Oh sorry I forgot we need to go ahead and call add disposable to and add that to our dispose bag and

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told you we'd use it.

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Anyway let's go ahead and clean this up.

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We're going to go ahead and move this in a little ways like so and we're going to call it from view

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to load.

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Bind submit button.

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Let's go see if it worked.

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So build and run.

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Open up your simulator and I'm really excited to see if this works.

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Guys if this is working the way that we think it is this is very similar to passing values using a protocol

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or passing values using a Segway.

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So let's go ahead let's pasand some names the way that we have been Kalib submit.

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Nice.

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How about Bob.

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Cool.

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OK.

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So let's go ahead and let's click this.

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It should present the view controller.

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OK.

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Just like we expected.

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And now if I type in a name like I don't know Amy and if I press submit what it should do is it should

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pass in value.

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And because of that let's go back to our main view controller because we passed a value on.

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Next we're going to take that name property pass into our names or re dismiss ad name Visi which is

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this one.

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And remember if we append a value to names or say how that's working is basically the names array is

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being joined with a separator.

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So when I press it watch what happens nothing because we forgot something very very important names

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array is a variable.

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We're expecting it to act like an observable.

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But if you remember a variable in and of itself is not an observable.

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It's like an observable but it can be used like a regular variable.

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We need to cast it as an observable in order for it to actually work the way we want.

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So inside you did load We're going to do that.

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We're going to call names right.

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Which is of type variable.

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We're going to call datt as observable.

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And now it's an observable we can subscribe to.

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We weren't actually successfully subscribing to the changes being passed into name array.

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So go ahead and call subscribe now that we can and we're going to call on next like you may have expected.

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And inside of Subscribe we're going to go ahead and set up the names label to be whatever gets passed

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in when we update names.

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Right now we do that in AD name Visi because we call on next we pass in value to the name subject and

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check it out when we are in the view controller here when we call on next for the name subject.

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We set the value here to append whatever name is passed in.

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So what we need to do is we need to basically set it up so that the values returned are actually set

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up to show in the textfield which we didn't do yet.

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Now we're going to go ahead and set up a property here for the closure and we're just going to say names

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in and in this just to denote that it's a closure.

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Names is a property that is going to hold the value of whatever was passed in when we subscribed.

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So go ahead and call self names label text and we're going to set this to be equal to names which comes

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in as an array of string and we can call DOT joined with separator comma and a space.

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And now this array is basically going to take the values that we had in the array but we are now able

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to pass them in.

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Thanks to our observable sequence.

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OK so let's go ahead and build and run this.

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Let's go check to see if that worked OK.

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You know what we're not disposing at though let's go ahead and call our disposable to dispose bag.

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It's not mandatory but it definitely can cause memory issues.

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If you don't do it.

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So let's go ahead and let's extend this a little bit.

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Let's build and run it again.

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Now that we're properly disposing and we'll see if this updates and works the way we expect.

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So here we go let's add in names the normal way Cayla we go Bob Jane.

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And now let's click add name.

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Let's go ahead and type in Chris and watch what happens when I click submit.

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It adds to the bottom view controller because we are setting the label to be equal to the names array

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passed in from our names here.

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Now we are subscribing to names IRA.

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That means whenever something is pushed into names array we get an array back.

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OK.

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And we can set our label to be equal to that.

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Names are joined with the separator.

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Now this is only because we are taking it from another view controller check it out.

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Down here we create an instance of ADD named VC and the name subject is where we are pushing in names

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from that other view controller.

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But when we push in a name right we take that singular name and we add it to our names array.

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Right now that is why up here this is this is why without this it didn't work because the values pushed

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in here are only reflected because we are subscribing to this names array.

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Otherwise our submit button here with the label it doesn't know how to interact with that because here

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when we push the submit button on the green view controller we are passing in the value just like that.

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This basically is what connected the two of you controllers.

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We created this as an observable.

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And whenever we push in a new value we're setting up the names label to include the newest data.

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That's what makes our swift super cool is you can do things like this that you would normally have to

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write a bunch of boilerplate code.

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But now I can just type in John and add him there or I could do another one Billy and add him there.

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OK.

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We're doing the same thing with a single asynchronous stream of data.

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So so cool.

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So guys this app is now finished and then the next section we're going to move on to our capstone project

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where we're going to build versey a get hub client using our swift.

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Very very cool.

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00:21:32,670 --> 00:21:34,020
Let's get over to that section now.

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Great job with this one guys.