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Hello and we're coming in on this list then we're going to have a quick introduction to the use of functions.

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We will have a section on lessons about the use of classes and object oriented programming and functions

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in the coming sections.

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But for now I thought it would be useful if we get the basic introduction to what functions are and

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why do we use them and how do we essentially use them and write them because we have been using them

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for a while now now it kind of makes sense that we know a little bit more about them.

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So functions are essentially the functioning part of an object.

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An object could have properties such as when you have a label that label has a property called text

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but also could have functions that does the things for us.

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We've talked about this in more detail in the future but for now we need to know how do we use them.

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So let's jump back into ex-cult and for this project I'm actually going to use on all U.S. applications

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simply because the way that we write functions in command line tools is a little bit different than

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the ones that we do you know in iOS up occasions and the command line is a little bit out of the scope

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of this course essentially.

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So I'm going to make a new iOS single view application and I'm going to call it functions by voice.

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So let's see what do we mean by functions.

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I'm going to go in here.

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I'm going to go to my viewpoint you can that I am not as you remember we can clear a lot of this out

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so we have a cleaner and tidy you know code.

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Not very overwhelming.

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And well I'm going to do is I'm going to say and Aslaug Hello.

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So what this does is very similar with a command line tool.

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When the app compiles on the application essentially launches in the simulator VBN see the command debug

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console and that's going to show us the value that we try to print.

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So now down in here it says hello which perfect Don't worry about that little thing up there.

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That's a machine printed you know.

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If if you have that depending on the application and the version of the simulator that you're using

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you might see different things.

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But this is the thing that we are seeing now here I want to add a new function.

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Let's see how do we do that.

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And then I'm going to explain what it does.

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I'm going to call this one my function and this is what my function does.

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It does this in a long Hello.

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So I currently have a new function in my project essentially in the implementation of your controller.

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Don't worry if you don't know what that is we'll talk about this in for more details in the future.

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But I have a new function which is actually quite similar to the Lord.

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You see it has a dash avoid the view of the alloy.

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I have it.

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I shall watch it.

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My function to call that I'm going to say self which means this column and file this client I see my

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function.

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So now I'm calling the function from self.

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So what do you think is going to happen when I run this application now when I relaunch it.

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Viewed that lot is going to happen because that's the one that happens by default and that the fourth

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is going to say Well go on find this function and run it and it finds this function says hello.

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Which is exactly what we expected.

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Now let's get a sense of what the function is or how it works.

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Every function essentially has these few things in it.

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I'm going to write them in comments.

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So it has a dash that shows it is not a construct or we'll talk about this in the future.

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Let's imagine there's always a dash and then within the Qantas's is the return type.

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It says what does this function return for us.

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And then there is the name of the function.

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And then there is a column an option or a column and then there is an all humans type and then there's

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an art you man's name.

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And this continues.

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Let's see what they have written it seems a little bit complicated.

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It actually is not is saying that there is a return type.

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What does this one pretend my function doesn't retain or anything it's return type is avoid it just

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does something.

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It's not like my function is meant to calculate somebody and give me a number.

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It simply means to print hello and that is saying what's the name of the function that someone.

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And then some optional arguments.

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Are there any arguments that you want to enter into it.

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Now that's a function that has an argument.

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So I'm going to go in here something right again boy and envoi I'm going to say my new function data

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has the identity of the type and this a string but I call it input.

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So let's see what this one means.

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It means there is a function called my new function.

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I receive is something called input.

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So it is going to call that going to say cell for my new function.

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And it says hey you have to feed me Genesis 3.

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I say OK this thing is a mirror.

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So now this function receives something but you haven't really done anything in here which we call the

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body of the function body of the function.

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You haven't done anything in your heart what we print that we say and the slogan perience what ever

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you will find in input.

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So whatever is the value that someone has fed into this function gets into the slot and gets printed.

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Let's see if that works.

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OK.

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So it says hello and then the other function.

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This fine print.

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I mean that's the one.

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Now bear with me for a few minutes.

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It will become a lot more you know a lot easier to understand now and clean or delete all of these functions.

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And I'm going to have a function that when you give it the number it returns the square effect.

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So I'm going to call it war.

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That is where function and my work function receives an integer let's call it input again.

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And what does it do.

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It says yins rez result is input multiplied by input.

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That is a squared value of something and log in a slide it says it's quite easy.

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What is it.

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It is going to be.

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So whoever calls this function and gives it a value it's really calculate the square feet and it gets

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printed for us the strike in the triangle.

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When I say sell a square function of eight let's run

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now I have it saying a square is 64.

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Exactly like how I expected.

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Now let's have another function that we give it to numbers it tells us which one is larger.

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So I'm going to delete all of these again.

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I'm going to say I have a void in my void which is bigger.

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These are obviously names coming up by solve our ints a and b.

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And that is going to be in beak.

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These are essentially high because you don't really need them but you want to separate your arguments.

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You have to put their space between them.

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Every human needs to know what is its type.

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In here both of them are integer.

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Maybe you're writing something that one of them is integer.

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One of them is a string.

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You should however mention or maybe you should have said this a little earlier.

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This lesson isn't for you to learn how to write functions you will get there in the future.

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This lesson is for you to understand how functions are being called and why do we use functions in general

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so don't worry overly about the ins and outs of the functions we will get there in a few sessions sections

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from now.

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So in any case if I receive an A and A B but I say if a is larger than B then and it's like are whatever

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is the value in a D is larger.

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And that is a else and this log what is the value is larger in B of course.

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So let's see how we can call this in my view that a lot because the method or the function that runs

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by default function runs out the value all the time.

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I'm going to say self which is bigger 5 and 15.

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And if you run this code now it's going to take a little while.

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And that is going to tell us 15 is large because it's calling that function.

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Now like I said the exact details of how do we use functions or how do we write our own functions is

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going to come up sometime in the future.

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What is important right now is understanding that how do we call functions and we do it using their

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bracket operations in Objective-C in swift and other languages.

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We do it slightly differently.

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Now I want to show you some of the functions that we have been using forever.

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Now one of them is the first I would say my name is equal to a string and then the other thing is either

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for instance.

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So that is essentially a function a function for a string.

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So just like for now in view controller I added my own function.

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Somebody has programmed something that is called is equal to a string that receives a string.

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Just make it here and returns a value that is Boolean or functions didn't return anything they want

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it.

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What that function essentially returns something it's the other one.

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Another one would be and this is throwing my a c r my A C R and that is going to be assisting a string

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format.

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Again this is a function somebody has programmed it's somebody out there or another one with B and S

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dictionary.

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My dictionary is this dictionary dictionary with objects and keys for instance a gain a function that

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somebody has programmed for us and that is how we call it.

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And then we call it that tells us well there's an argument that you have to feed me.

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So with that in mind let me just quickly recap this.

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Here is again the same thing I had written earlier on.

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So return type that is a return type of function name an optional call.

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All right.

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You meant type arguments.

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Name that is how a function is produced.

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And that is how we use it.

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Again we will be writing functions in more details in the future.

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But for now when you're using functions keep your eye on the types that is returning and the arguments

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that it's accepting.

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For instance if you have something like this immutable a string my A C R and that is going to have DNS

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and mutable a string the string weight or string.

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You see it says it's instance type return.

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So whatever is its own type.

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It will return the same thing.

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It will return and ask new to the string and it needs non-call and it's a string so you have to feed

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me with a string.

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If I do that I say well I have to give you a value or something.

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Doesn't matter one way it cannot be null.

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It has to have an actual value in.

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So keep an eye on those and you get more familiarity and you get more confidence in dealing with functions

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and calling methods and from different objects in your Iowas program.

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So that's about that.

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Let's keep it up to here and we'll move on to our next lesson which is actually a very interesting exercise.