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All right.
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So in this lesson, I want to talk about Swift Structures versus Swift Classes.
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Now, it's really important to state that I'm talking about Swift Structures in particular, because even
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though different programming languages, a lot of them will have these things called struct.
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They have different capabilities.
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And from language to language, they actually behave quite differently.
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So it's important to realize that we're just talking about the structures that are in the Swift Programming
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Language. Now, to create a structure,
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it's pretty simple.
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You would create it just as you would any class and you simply replace the keyword class with struct.
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Now, the naming convention for structures are, again, the same as classes.
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You will start off with a capital letter to name your structures which is different from how you would
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camel case your property names or your function names.
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Now, structures in Swift can have properties as well as methods, and they can do almost everything that
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classes can, but they work a little bit differently.
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Now, a lot of times whenever I give this talk, students will ask, "Well, which one is better, struct or classes?
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Which one comes out on top?
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And this is very similar to another question that I often get which is which is the best programming
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language to learn?
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And they both have the same problem.
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There is no such thing as one is better than the other, but you should see everything inside programming,
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be it a programming language or a component being tools in your tool belt. and you should choose them
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in different scenarios and for different purposes. I'm just saying, you know, which is better struct versus
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classes. It's kind of saying like which is better, a horse or a mule,
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right?
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They both have their uses.
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They both have their pros and cons. Now, similar to a mule,
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a struct is infertile.
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So just as you can't mate a female and a male mule to create a baby mule, you also can't inherit from struts
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or try to subclass in a struct.
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Inheritance is reserved for classes and this is one of the biggest differences between structs and classes
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and when you would use each, whenever you need inheritance.
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So if you're working with object-oriented programming, we know how important inheritance is.
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So far, none of our user interface components have been created from scratch by us.
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We've always been inheriting UIView or UIViewController or UITableViewController, and this
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capability is not given to structs.
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Now, the other major difference between structs and classes is that they live in different places in memory.
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So in computers and that includes handheld computers, such as the iPhone, there's two main ways of storing
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data for random access.
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So this is referring to the RAM or the part of the memory that needs to be frequently accessed and it's
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not the same as your permanent storage, such as your SSD or your hard drive. And stacks and heaps are
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simply different ways of organizing the RAM and they're used for different purposes.
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So let's say that you're working at an office, a stack might just be that a stack of papers which you
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have to get through from top to bottom, but a heap could be just a random heap of all of your files and
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folders.
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Now, structs live on the stack.
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And the thing about the stack is that it follows something called a first in, last out system.
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So that means that the first piece of data that went into the stack will be the last one that pops off
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the stack,
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and this means that the most recently saved pieces of data will be on hand and quickly accessed when
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you need it.
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Now, classes on the other hand, they live in the heap.
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And if we create a new class that's called MyClass with a property and a method,
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then when we initialize our class, let's call it MyClass.
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Then all of that data gets allocated some memory and it will be saved somewhere in the heap.
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Now, in order to find it in the heap, our class also has a reference in the stack.
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So if our class was called MyClass, then that reference MyClass will be put onto the stack, and that
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reference will point towards our allocated block of data in the heap, so that when we need to access
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something inside this object MyClass, will be able to locate it using the reference MyClass.
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Now, another common thing that you'll hear when people are discussing struct versus classes is that struct
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of value types.
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And this means that they stole the actual data values.
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Now, classes are reference types and we store a reference to a block of memory, and the reference is just
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an instruction for how you might locate that block in the heap.
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Now, what's the difference between value and reference types?
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Well, if I was to copy a struct or a value type in this case, then it would create a new copy that has
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exactly the same values.
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But if I was to copy a reference type, so a class, then I would copy only the instructions for how to
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locate the block of memory inside the heap.
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So this is a really important concept,
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value types and reference types.
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And so in order to understand it better,
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let's head over to playgrounds and do a deep dive into how they work and behave in real life when we're
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writing code for structs and classes.