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Hey everybody what's going on this is Caleb with slopes dot com and in this video we're going to continue



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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.



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OK we're going to give it a few properties and initialiser and then we're going to create some incomes



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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 wups class question and then we need some properties here we need a question type.



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So go ahead and type of var type.



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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 answer of type string as well.



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Go ahead and set them up by typing self-deceit 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-talk queery equals queery and self-taught.



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Answer equals answer.



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Now it's going to yell at us until we create our question type ENM.



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So let's do that now.



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OK so below are a class type ENM question type K.



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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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In case essay four 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 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 type in answer type of type string and we're going to create the same cases case true false



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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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Multiple choice.



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We're going to say Sergeant Pepper 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 my my my thought on how it works anyway.



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So we have four question types for answer types.



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They have explicit values and we can initialise a question K 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 going to 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 and it's just a



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way to kind of compartmentalize and put features in a certain place where they need 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 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 but now we need to be able to generate a random in 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 a 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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OK.



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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.



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OK so let's say this generates a number 2.



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Now in our incomes we need to be able to allow number 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 Inam 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 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.



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But we're getting an error here.



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Check it out.



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Anime's may not contain stored properties in order to circumvent this we can create this as a static



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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 type's array and we're going to pass in random Numeral.



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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.



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And it's saying that we have not yet returned a question.



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That's because we have not yet returned the question so let's keep building it.



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Remember a question needs a type a 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.



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That's my question.



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OK.



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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 in numeration and we can pull out the specific type using



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our 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.



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Answer type types and I can pull out the right value using random numeral k that will get the proper



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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.



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Let quiz equals quiz.



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And then I can call quiz dot.



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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.



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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 dot type K and you'll see it will 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 queery 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.



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That's not an answer question that 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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That could be my question and I could create a an answer type here.



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You know what just for time let's just go ahead and just create a class here of type answer just so



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that it doesn't yell 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.



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You can sort of subclass protocols as well which is really neat.



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



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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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K 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.