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So we're coming again in this exercise.

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You're asked to do this you need to have an interface that has a button on or so it has a label.

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And every time that you tap on the button in name of a city should be randomly displayed.

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So every time they pop a button a city name should be chosen randomly and it should be displayed on

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the screen of your iPhone or iPhone simulator.

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So good luck our the we don't try to do it on your own.

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And once you're done you can look at the way that I do it as well and hopefully we'll get it done.

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OK.

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So let's jump back into Scott in here.

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I'm going to start a new project this new project I'm going to call it I have to reveal the in my top

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to reveal.

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I'm going to go to my main storyboard in my main storyboard.

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I'm going to have a button on that bottom just like the last time I'm going to place it somewhere up

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there.

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For now we don't really care about the design.

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There's you know where exactly we want to put objects and in here I'm going to say it's this color is

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like.

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And it's gone is maybe pink.

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And it says how to review.

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And then there is a label and this label which is here it's going to be there very similar to are actually

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identical to what we did in the previous lesson.

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I'm in here I'm going to go ahead and say My background is actually dark gray or maybe I don't like

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green and that I'm going to go to my assistant later and I'm going to go to my age just like the last

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time and remove everything.

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Say this is the action.

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So my boy then calls the action top to reveal the auction.

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You don't really have to give such elaborate names but you know you're welcome to do it.

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And I usually do it like this especially when I'm teaching but if I'm working on something for a project

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I try to stick to short term names that I have a property for the label.

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Let's call it resolved labor and that's about that.

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So one of them is a property.

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One of them is an action.

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So let's go ahead to our code.

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I'm going to go to the AM.

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As always I'm going to clear things out.

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Get rid of that.

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That's my deal with the Lord.

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And this is the function that they want something to happen.

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So what they want to happen is I want to show a random city.

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So let's go ahead and do this.

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This array.

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This array is called cities.

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And that's going to be honest.

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They out.

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And in it with objects and the objects are Vancouver Sun Cisco I'm finally learning how to type that

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New York may be harsh and high if that's how you spell it.

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I'm going to stack them properly in here and or in here.

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And of course in here nice and tidy and then I have to get one of them randomly to get one of those

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cities randomly I'm gonna say.

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And it's a string.

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It's it the random city random city is going to be cities array objects that index for the index we

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have to put a random value.

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So I'm going to say integer random index is going to be all for random Let's get it modulus for which

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is going to give us 0 1 2 or 3.

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Or better yet let's get it modulars cities that count.

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So it gives us the exact dynamic result of it.

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So that's the random index and that's the object that I want and of course finally I'm going to say

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result labor resolves to label dot text with with an underscore of course.

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What's going on here.

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There there's an hour before that.

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So all on this go a text that becomes the around Sefi and that's about that.

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So let's run this.

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I just realized this is from New York.

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I have a spell Turk sob.

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You know what to.

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That's going here top to reveal in San Francisco San Francisco San Francisco Toigo Vancouver.

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Kind of getting all of them one at a time.

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Now while this isn't working and it's all well there is a bit of a design flaw in this program and a

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design flaw that we are having is this Every time I'm tapping on real action.

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What's happening is it's really initialising an instance of an array called cities.

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So every time I stop there is a new array being produced and that's really not a good practice simply

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because your array of objects are not static like these are probably being read from some sort of a

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backend or a network or some it is being provided to you.

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So you shouldn't be really initializing it you have to just be using it.

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So wouldn't it make more sense if we actually declare them define this array once at the beginning and

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then every time that we stop we just use it.

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So I'm going to go cut this whole part out and then I'm going to put this entire thing in my view that

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lot which means every time the viewer loads.

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Please go ahead and declare and define an array for me that is for cities which makes all the sense

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it says do it just once at the very beginning.

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We are however running into a brand new issue now and that issue is this.

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It's called the scope of a variable dislikable N.S. our cities is being declared within the boundaries

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of the body of the view of the Lord.

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So anyone outside of here doesn't have access to it.

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So in here the error says the use of undeclared identifier cities.

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It says I don't know what it is.

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How are you trying to access something that I don't even know what it is.

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And that's simply because cities is what we call low call to this function only to view that lot only.

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So to remedy that there are similar or different solutions.

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Some of the most notable solutions are converting the cities into a property or placing them within

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a private interface.

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If you remember in the earlier stages of this application or any brand new application you'll have something

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like this interface of your controller and and and that's essentially a private interface that holds

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onto the properties that you want to use in this application.

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I am however not going to use any of these.

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I'm going to use a much simpler way and that is I'm going to go outside any of the methods outside the

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function off of you that load or outside the function of top to reveal what I say here is the declaration

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of MSRA.

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So it says declare a and as array.

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So there is a something called the cities and then inside the view of the Lord I'm going to get rid

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of the odd declaration.

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So this is the declaration and this is the definition of hate or what is in it it's being allocate and

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initialized.

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And here I'm using them.

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So this will work.

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But before we jump into actually running this application let me explain this really quickly why I wasn't

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getting an error or why I was having this in year 1 declaration inside the view that load another declaration

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outside because each of the declarations would work independently in their view that they would have

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a called object called cities.

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And then we'll have a.

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Somehow you could call it a global object is not exactly global.

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It is a class property but it would have a class property called cities and that cities object was this

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one.

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So this application would actually crash not simply because whatever is in the cities is not the same

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as the one in here.

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These two have nothing to do with each other because this is a brand new copy of it.

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So to fix that we said let's declare it just once and get rid of these.

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So if we define it once in here as of yet another thing I should mention is that while this is perfectly

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valid to have the same name for two properties one of them in a different scope another way in a different

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scope.

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It's really not a good practice because it kind of confuses you about which one is Veach And why are

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you using them in a certain way if you need a variable that must have a certain name and there must

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be two copies of it which is a very rare situation.

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But in that case make sure that each of the names you modified in a way that you know which one is the

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local one and which one is the one that everybody can access.

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So I'm going to get you out of this.

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So now when are we in then everything.

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And then I have my MSRA set is when the view Lote's cities gets what we call populated.

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It gets all of its elements inside it.

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And then when the top thing would happen let's see that in action

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top to reveal that now finally before I close this lesson just a bit of a housekeeping and this isn't

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really all that important but it's somehow good for us to get a sense of it.

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We don't really do a lot of stuff in our view the Lord because if we do soon enough our view of the

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Lord function will be cluttered with so many many different things happen.

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Instead what we try to do is we try to put every bit of code inside a new function and we just call

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all of those functions.

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So here I'm going to say there is a function called populates aere which is going to put all of our

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objects inside the array.

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And this is that guy so populated area is going to be here.

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And then in my view of the Lord I say that moment the view Lords do this superb You know that's a system

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thing.

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And then I say self populate right.

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So this way I have properly organized things.

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And if you want you can actually fold.

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It's called that by holding the command but then clicking on it.

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So if something is you know something that you do it once and then you are not going to worry about

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it for a while.

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You can fall dead.

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Another thing you can do is you can actually cut it and put it somewhere at the bottom of the record.

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So if you don't really worry about this one for a while now all we care about is doing this thing simply

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because in here we have gotten to see how an array is populated and once we have the objects in it that's

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all we care about from this point on we care about here.

153
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What's going to happen then the top.

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So that's about that.

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We call that function and then this function gets called only when we tap on it.

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This one gets called right at the beginning of the view.

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So with that let's keep it up to here on we'll move on to our next lesson.