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Hey everybody what's going on this is Caleb with slopestyle.

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Com and in this video we're going to continue talking about protocols and delegates.

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Except this time we're going to see how they can be useful in classes and structures specifically classes.

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But the same principles apply to structures as well.

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So we're going to remain in the same playground as the last video but I'm going to make some space just

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so that it's like we're using a new one.

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Go ahead and we're going to actually begin by creating kind of a quiz generator that can generate a

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random question and we're going to write a class for a question OK we're going to give it a few properties

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and initialiser and then we're going to create some incomes for question types and answer types.

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So let's go ahead and let's just begin with our class 4 question.

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Go ahead and type.

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Whoops.

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Class question and then we need some properties here we need a question type.

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So go ahead and type var type and that's going to be of type question type which we have not yet created.

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We will below in just a moment.

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Go ahead and type var queery of type string and var answer.

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OK those are the things that every question should have below.

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Go ahead and give it an initializer and pass in a type of question question type a query of type string

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and the answer of type string is well.

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Go ahead and set them up by typing self-taught type equals type.

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Of course that's not going to work because we haven't created the question type.

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ENM self-taught query equals query and self-taught answer equals answer.

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Now it's going to yell at us until we create our question type enough so let's do that now.

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OK so below are a class type ENM question type K and it's going to be of type string.

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Because each question should have a string value right.

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That's where the words of the question will come.

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And we're going to create four different question types here.

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Go ahead and type case.

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True false case multiple choice.

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Oops that's with A's C case.

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Short answer

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and case essay for different kinds of questions.

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And let's go ahead and let's give these each an explicit value just for this example by typing equals

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and a string here and we're going to just say is the sky blue.

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There's my true false question.

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Wait that's not a question.

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How about the sky is blue.

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True or false.

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Multiple choice we're going to give some options here.

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Who is the ugliest Beetle.

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Well I guess Colin John Paul George or Ringo.

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I have my opinion but I'm not going to say it.

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Short answer will be what is the capital of Oregon my home state.

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And for the essay.

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Let's give a nice really easy question here.

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How about in 50 whips in 50 words.

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Explain molecular fusion.

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Easy.

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OK great.

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So there's our question types.

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Next we're going to need answer types as well.

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So we're going to just create static answers for these questions and let's do that by creating an almost

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identical enumeration called answer type.

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So go ahead and type in answer type of type string and we're going create the same cases case.

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True false case multiple choice case.

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Short answer and case essay.

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Now we're going to give these explicit values as well.

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The sky is blue is going to be true.

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K multiple choice.

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We're going to say Sergeant Pepper.

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We're going to obviously get that wrong.

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We're going to say the short answer is Salem.

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If you knew that.

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Bonus points for you.

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Ding ding.

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And the essay will say molecular fusion happens when a daddy molecule and a mommy molecule love each

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other very much.

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It's not really how it works but that's just it's just my my my thought on how it works anyway.

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So we have four question types for answer types that have explicit values and we can initialise a question

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of type question.

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So pretty cool.

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Now what we're going to do is we're going to create a protocol and we're going to give it a method and

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it's going to basically be a blueprint for our question generator.

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Let's say we're building a quiz app.

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And of course this data would probably come in from an API pulling random questions but we need to basically

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set up a blueprint that's going to allow us to generate questions when we need to.

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So go ahead and type protocol question generator and inside our protocol we're gonna declare a method.

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OK so go ahead and type phunk generate random question and we're going to actually have this return

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a question to us but remember we don't have any kind of implementation inside this protocol so we don't

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need to put curly brackets we don't need to write any code.

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The protocol is just the blueprint.

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So basically this this helps us to include what we actually need and to include the kinds of functions

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that are required for a certain feature.

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So if we conform to the question generator protocol maybe in a quiz class later on.

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It basically reminds us hey you need to be able to generate questions for this quiz.

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And it's just a way to kind of compartmentalize and put features in a certain place where they need

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to go.

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So now that we have our protocol here and we have the function generate random question that returns

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a question we can go ahead and create a class for our quiz case.

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So go ahead and type class quiz.

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And we're going to conform to the quiz generator

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protocol like so.

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OK.

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But it's going to throw an error at us it's going to say hey we don't have that type.

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And that's because.

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Oh no wonder that's because it's a question generator.

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OK.

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There we go.

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Question generator and it's going to throw an error at me saying that we have not yet conformed to question

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generator.

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That's because we are missing our blueprint instructions.

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Generate random question.

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So inside of this class I'm going to go ahead and I'm going to call generate random question and you'll

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notice the error goes away because we have added all the functions that question generator says we need.

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We have not yet done anything with them but we've at least called the function.

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So that's cool.

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But now we need to be able to generate a random question here.

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So let's go ahead and let's think.

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I want to basically choose a random question type and then I'm going to basically pass in the values

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needed to generate a question which is a type of query and an answer.

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So let's go ahead and let's generate a random number first.

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OK so let's just say let Rand numeral equals and we're going to use arke for random uniform.

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And we're going to set an upper bounds of 4.

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Now that's going to generate numbers between 0 1 2 and 3 K for values which is perfect when dealing

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with the index of something.

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So that's really cool.

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The issue though is that we're actually going to need this to be of type int and not type you and if

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you look you'll notice that arc for random uniform returns a 32.

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So let's go ahead and type in it and we're going to pass our arc for random uniform function into that

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so that it is of type integer k.

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So let's say this generates a number two.

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Now in our incomes we need to be able to allow number 2 which remember if we're dealing with an index

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number two is really the third result.

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So that would be short answer but an enum in and of itself does not have any kind of indexing system

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or a way to identify first second third fourth.

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So what we're going to actually do is inside of our ENM we're going to create an array and we're going

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to basically just let We're going to pass in all of our types so that we can order them in some type

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of way.

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So we're going to go ahead and just type let types and we're going to go ahead and pass in true false

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WIPs true false multiple multiple choice.

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Short answer and essay.

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OK.

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And this this array is going to allow us to parse through and I can pull out the index here at index

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1 and I can pull out multiple choice K that's going to be how we identify the different types that we

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want but we're getting an error here.

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Check it out.

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It may not contain stored properties in order to circumvent this we can create this as a static constant.

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OK.

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Now a static constant is basically going to allow this to exist for the entire life cycle of the app

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since it's static.

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And we're going to use that because we need to be able to access it all the time throughout this when

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this code runs.

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Now this is great for questions but we're also going to need it for our answers as well so I copied

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it and I'm pasting it down below.

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So we have a random number.

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Now we're going to need to use this number to basically pull out a random type from our Random type's

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array inside of our enumeration.

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So go ahead and type let random type equals question type and what we're going to do is we're going

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to pull out our types array and we're going to pass in random numeral k.

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Now let's say that was two or three whatever it is it's going to pull out a random one.

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Now as it runs you'll see but we're getting an error here and it's saying that we have not yet returned

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a question.

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That's because we have not yet returned a question.

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So let's keep building it.

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Remember a question needs a type of query and an answer.

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So let's go ahead and type let a random query equals random type and we can pull out the raw value.

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Remember if I pulled out multiple choice the raw value is going to be the string here that's my question.

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Easy enough.

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So there we go.

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Let random answer equals.

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And where are we going to get the answer.

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We're going to get it from our answer type enumeration and we can pull out the specific type using our

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array.

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Now if I pulled out multiple choice here I can use that same numeral value here to pull out the multiple

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choice answer.

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So let's go ahead and let's call answer type types and I can pull out the right value using random numeral

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k that will get the proper answer back for me.

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So now that we have those three values we can create a question.

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So Type let.

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Random question equals a question and we're going to instantiate it here with our random type random

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queery and random answer.

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OK.

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Now at the very end we need to go ahead and just return our Random question.

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That's not a question of random question.

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There we go.

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Supercool so as it goes through the function will properly generate the value we need.

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But I'm noticing that it is giving us an issue here.

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It is saying we cannot convert answer type to expected argument string.

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So random answer is coming in.

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But we are just getting a random type here we are not pulling out the raw value.

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Oh that's right.

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So instead of that at the very end here I can go ahead and pull out the raw value for the item we pull

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out of that index.

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And now that error should go away.

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Really cool.

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So that's great.

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Now we have a quiz we have conformed to the question generator protocol and we have put in all the implementation

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code to generate a random question from our enumerations.

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So now if I create a quiz check it out I can type let quiz equals quiz and then I can call a quiz.

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Generate random question and watch what happens when I do that.

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It runs and it pulls out a question K supercool.

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Now it pulled out a question type of essay and it pulled out an answer from our answers array.

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Now we have a type a query and an answer.

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That's so cool.

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So let's go ahead and let's actually print out what's happening here and actually what I'm going to

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do is I'm going to put this inside of a constant like so so that I can actually pull this out.

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So let's just say question type whip's type and I can pull out.

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Question.

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Question datt type K and you'll see it print question type multiple choice.

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OK then we're going to say queery And you know what while we're at it why don't we just go ahead and

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do forward slash and to give us some space here.

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And for the query we're going to pull out.

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Question.

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Queery and then slash and space and answer we can pull out.

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Question Answer That's not an answer question answer.

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So there we go as it prints we should get everything cool.

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Question type short answer.

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Queery What is the capital of Oregon.

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Answer.

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Salem everything shows up exactly as it should.

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This is how powerful protocols are.

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It gives us the ability to basically create requirements that must be conform to when using that protocol.

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And the cool thing is we can do a bunch of different things like lets say I wanted to create a new kind

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of protocol maybe one that generates answers and then you would have to do the questions kind of like

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Jeopardy.

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So lets just go ahead and do protocol answer generator and a protocol can actually inherit or conform

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to another kind of protocol.

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So that's really really cool.

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Now if you wanted to you could use this as a way to add additional functionality so phunk generate random

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answer.

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OK.

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That could be my question and I could create a an answer type here.

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You know what.

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Just for Tiflis just go ahead and just create a class here of type answer just so that it doesn't yell

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at me.

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And if I wanted to I could create a class called jeopardy.

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And I can conform to my answer generator.

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OK which is really cool but you'll see it's going to yell at me.

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It's going to say hey you have not yet conformed to answer generator.

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Now I can go ahead and type generate random question or generate random answer because I'm conforming

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to that protocol through my other protocol.

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So you can do it just like you can subclass classes you can sort of subclass protocols as well which

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is really neat.

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So let's go ahead and let's conform to generate random question.

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Whoops.

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So let's go ahead and let's conform to generate random answer and you'll see we're still not getting

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conformance.

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And why is that.

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Because we're not generating a random question as well.

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In order to conform we have to meet the requirements of both to generate random answer and generate

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random question.

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That's just something we need to do.

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That's part of the power of protocols you can create a bunch of nested protocols just like that's pretty

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cool.

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Now of course we're not returning anything here so it's going to yell at us but I hope you can see how

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helpful protocols can be and at least some small ways.

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And in the next couple of videos we're going to build an app that allows you to pass values back and

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forth between View controllers using protocols as a way to delegate information.

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It's called the delegate method and it's something that's commonly talked about with protocols we can

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use protocols to delegate information to other classes because remember a protocol itself does not contain

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any implementation we implemented on a controller.

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And so using conformance between two to view controllers we can use protocols as a way to delegate that

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information.

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It's really really cool.

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So let's go ahead and let's head over to the next video and let's build it out.