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Hey what's up.

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Jack Davis here with Defoe's dot com.

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And tonight we're here to talk about a very popular subject over the last year or so and that subject

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is protocol oriented programming.

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There was a talk given w DC in 2015 that generated a huge amount of buzz on this subject.

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It continues to generate buzz to this day sometimes is referred to as the crusty talk.

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I highly recommend that you watch this session if you haven't already.

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What edition of protocol extensions protocol oriented programming has become even bigger.

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And in this introduction we're going to cover a few different topics such as swift tops the differences

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between object oriented programming and protocol oriented programming protocols themselves protocol

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extensions and generics.

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Then to wrap things up we'll take a brief look at practical real world examples of how protocol oriented

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programming can be used in your own projects.

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Now this is just an introduction and this is a topic that can get very complex.

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I hope you're as interested as I am and digging in continue learning new ways that protocol oriented

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programming can help you to write better code.

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There is a ton of information out there about it.

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With that said let's move on and get started.

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First we'll quickly cover the swift type system.

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So for the first part of this segment we're going to talk about swift types and I'm going to pull up

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a whiteboard at appears so I can sketch those out for you.

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This is just going to be a quick run through.

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Hopefully you're already familiar with them.

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Some of the things you may not be familiar with but we're going to go ahead and lay those out just because

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they may come up later on.

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So let's pull up a white board here.

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All right.

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So we've got swift tops

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and basically swift taps are broken into two categories.

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We have nine tops

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and we have compound tops and we're not going to talk about compound tops for a whole lot but I'm going

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to go ahead and lay them out here just so you know how it works.

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Compound types.

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We have a group of top set or functions.

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And the reason I say it's a group of tops is because it includes functions themselves

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as well as closures.

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And then also in compound types we have tuples

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and I don't know if you're familiar with tuples or not you may have seen them in code before.

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It's basically where you have two two or more types enclosed in parentheses.

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You can pass those around in your code if you don't know what tuples are highly recommended that you

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looked at.

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Those are very handy in certain instances.

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So let's look at nine types and that's mainly what we're going to focus on here and under nine types

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we have we have primitives

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and primitives are things like integers doubles strings characters things like that in most languages.

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Those are all just built in to the language in swift they're handled a little bit differently they're

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actually implemented in the standard library structures.

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Most of them anyway and will will probably take a look at that a little bit later.

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I just want you to understand that in swift the way that they create those is they take structures and

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they put extensions in there to give them functionality that's built into other languages.

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So we've got primitives.

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So we've got so primitive as a name type but it's also a value tot and undervalue types besides primitives

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we also have structures

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and gnomes or enumerations.

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All right.

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And then also under the name types we have reference types

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and it's kind of important to understand the difference because if you don't it could cause problems

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and under reference types of classes.

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And with this being a little bit more of an advanced topic hopefully you are familiar with Object-Oriented

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Programming and classes and a lot of times we just kind of default to using classes.

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But we're going to talk about object oriented programming obviously.

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And the fact that sometimes classes aren't always the best answer.

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Sometimes it's better to use a structure or it as a value type.

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And basically what that means is value types are passed as copies.

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So when you say the eraser.

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So let's go ahead and clean this off here.

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So we're going to talk about the way objects are created.

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So if we have a reference type if you remember that would be a class

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and we've got a value type over here.

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And for this case we're just going to say a structure.

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So over here we've got a class.

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And over here we've got a struct.

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Now if you create an object out of each of these things so say we do a variable and we'll say car one

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equal to an instance of a car

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OK.

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And then over here say we implemented car as a struct instead of a class so we can save or we'll save

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our car one equals car again.

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Now obviously on the left side we've implemented a car as a class on the ride as a struct and then if

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we come in and we save our car two equals car 1 and we do the same thing on the other side

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we have two different things here on the class side or the reference side.

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Both of these instances point to the same object.

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So if we did something like car to dark color and the default color was blue if we do something like

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car to color and we say equals red since that's a reference and they both point to the same thing car

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one

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color is also going to be red.

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Now the end on the stroke side which is of value it's passed by value.

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So when you make this assignment in this line right here what that does it doesn't copy a link or reference

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to a car too it makes a copy of the actual data and passes it as a copy.

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So if we do the same thing over here

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when we say car to talk color equals red car one color is still going to be equal to blue.

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And it's kind of an important thing to understand.

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In most cases we keep up with the flow in our programs and we know exactly what's going on.

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And if you get in a very complex hierarchy and situation you've really got to be aware that if you set

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something in one part of your code that you don't have unintended consequences and another part of your

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code.

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So that's kind of the point of this here's just demonstrating that classes are passed by reference.

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So if you create if you set something to a copy it's not a copy it's a reference they both point to

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the same thing whereas a value type.

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It passes it as a copy and there's places where reference types are better suited for the task.

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And there's other places where value types are suited for better suited for the task.

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Apple always recommends going with a value type wherever possible to quote parts of the WWT see 20:15

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video I spoke of earlier.

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Strokes are preferable if they're relatively small and copyable copying is way safer than having multiple

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references to the same instance.

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Especially important when passing around a variable to many classes in a multi-threaded environment.

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If you can always send a copy of your variable to other places you never have to worry about that other

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place changing the value of your variable underneath the strokes there is no need to worry about memory

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leaks or multiple threads Reisen to access a single instance of a variable.

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Classes can also become bloated because of class can only inherit from a single superclass.

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That encourages us to create huge superclasses with many different abilities that are only loosely related.

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Use protocols and protocol extensions allows us to eliminate the need for classes to achieve that sort

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of behavior.

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That's the official word from Apple on the subject.

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Struction gnomes are preferred and classes should be kind of like a fallback whenever they make sense.

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There are some instances where classes are going to be the only option you have.

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Anyway I hope you enjoy this intro and I'll look forward to see you later.

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Later.