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Welcome to a Swift Deep Dive on Parameter Names. Now, in Swift, the parameter names of a function are incredibly
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important. In the predecessor to Swift, Objective-C, which used to be the language that we used to make
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iOS apps,
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they weren't really big on parameter names.
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Instead, you ended up with really, really long method and function names to describe exactly what the
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function is supposed to do. But in Swift, it's meant to be about well-named parameters that clearly describe
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the functionality. And this ability of Swift methods and functions, to be really clear, relies really heavily
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on a particular feature of the Swift parameter names.
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And it's the ability to have completely separate internal and external parameter names.
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So in this case, instead of having a single parameter name, the word "name," we now have a external name
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which is the name that will refer to the parameter when we call the function, and an internal name which is
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the name that we'll use when we need to use the parameter within the function.
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So if this is what our method definition looks like, then when we call the function, we would write something
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like this. So in this case, the external parameter name is what we're using when we call the function, and the
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internal parameter name is what we use when we need to use the value of that parameter within the function.
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Now, you can also if you wanted to, actually omit the external parameter name altogether to be able to
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call your function just by passing in a value without mentioning the name of the parameter at all.
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So how would we do that?
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Well, all that we would need to do is simply turn the external parameter name into an underscore.
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And now we can call our function without using a parameter name at all.
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And instead, all we have to do is just pass in the value that we want to use as the input.
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So in this case, we still have an internal parameter name which we can use to refer to the value within
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the function.
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But when we call the method, we no longer have an external parameter name.
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So in the next lesson, we're actually going to use this in practice and we're going to update our delegate
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methods to be more in line with the way that Apple does things.