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Everybody what's going on this is Caleb with slopes slopestyle.

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And in this video we're going to talk about one more kind of transformation.

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It is the filter function and it is really really cool.

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I love filter and I actually use it for a lot of things.

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We're going to use it later in this course in the GET hub client that we'll build but for now let's

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go ahead and pull open our X playground and let's figure out how it works.

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If you think the name sounds like we're going to be basically filtering data.

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Yeah that's that's exactly what it is.

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So go ahead and.

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Right click on flat map click new playground page and we're going to name this filter.

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All right go ahead and select all and copy in those lines that we need are x swift playground support

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foundation and needs indefinite execution of course like the last video create a Dispose bag by typing

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let dispose bag equals a Dispose bag.

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OK just like that.

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There we go.

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And now what we're going to do is we're going to create an observable and we're going to pass in five

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different string values.

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OK.

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We're going to use a filter to basically filter out some of those values and store them in their own

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array.

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That's what filter does.

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Then we're going to subscribe to that observable and print out the values.

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You'll see how cool this is and how it works.

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So this is going to be an observable that's going to hold some famous CEO names.

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So go ahead and type observable dot of and we can pass in multiple elements to observable dot of k.

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And what we're going to do is we're going to pass in.

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Ilan for Elon Musk we'll pass in Steve for Steve Jobs.

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Jeff for Jeff Bezos mark for Mark Price of course and Jack for Jack Ma of Ali Baba.

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So we have an observable consisting of five string values that all happened to be CEO names.

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Now we can do is we can call DOT filter K and the cool thing with filter is that inside the curly braces

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we can set a condition and what it's going to do is it's basically going to look through every element

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and it's only going to return values that meet that condition the values that meet that condition are

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going to be passed into a new observable only containing values that met the condition you set.

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Then of course after that you can subscribe to that and print it and do whatever you want with it.

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So what we can do is we can use dollar signs 0 K to capture the value that passes through that's our

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temporary variable and we can call anything that can be called upon a string.

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So I'm going to use starts with sequence K and my sequence here is going to be J.

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I want to pull out all the CEOs with the name J.

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That's my condition.

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So at the end what I can do is I can append another function.

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OK let's actually do some cleanup here let's pull that down.

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Let's indent this and indent this.

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Now what I can do is I can call DOT subscribe.

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OK because now I'm subscribing to the observable that's created by this condition.

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I want to call on next because that is what happens.

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Every value that is passed in is gonna call in on next call.

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OK.

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And now I'm going to go ahead and inside of subscribe I'm going to print dollar sign 0 to print out

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that observable.

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Watch what happens.

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I get Jeff and Jack that's it.

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It subscribes.

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It goes through and prints out every observable of my condition that I set.

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I filtered only names that start with J.

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How about S.

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If I were to do that.

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I only get Steve.

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How about let's do another condition here maybe contains.

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Maybe.

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I want it or not.

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Sorry it contains.

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Well how about contains character.

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Let's do of type character.

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And we're going to pass in a string value there for the character.

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So let's say if it contains an A.

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Let's do that with a string.

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If the name contains an A and it'll conditionally cycle through here.

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There we go.

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Sorry.

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Sometimes it takes a little while to think and do its thing.

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There we go.

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So I get Mark and Jack those are both CEO names with a.

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How about Withey OK.

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I get Steve and Jeff probably thinking what about Ilan.

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Well I use the lowercase e.

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And so that is where this can be problematic.

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You have to set some conditions for capital and lower case.

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But as you can see when we go back in time here and undo what I just did do starts with J again as you

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can see this prints out the values for the condition I've set.

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I filtered my observable You can also do this with arrays just by the way you can fill it.

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You can set conditions and filter elements out of arrays or dictionaries and it's just a really cool

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thing to do and are as Swift it's really helpful for parsing through certain bits of information.

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So of course at the end we need to add it to the Dispose bag do that every time and we'll go ahead and

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just return down there.

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This is how filter works guys.

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This is this is it basically you call filter on an observable or an array or whatever you call filter

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at the end and whatever happens whatever condition you set is returned back.

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If an item meets that condition then that observable gets passed to subscribe and when the next is called

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You can print out the value you can do something with it set it to be a label set it to fill a table

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view whatever you want.

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You can use then at the end we always add it to our dispose bag.

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That's just something we do.

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So this is how filter works it's very cool very robust lots of amazing uses for this and it's really

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clean as well which is why I like using it.

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So we're going to move on to the next video where we're going to learn about the last transformation

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that you will learn about in this course called Zip Zip is really cool it's going to let us put two

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observables together into one in a new way a little bit of a different way than you have seen already.

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So let's head over to the next video and let's do that.