When would I use a function instead of a closure

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Created Nov ’20

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I come from a VB background (and lots of other languages), and now I'm learning Swift. I just reached the part about closures, and I've been searching for an article about when a function is to be preferred over a closure, and I haven't found any yet.

It seems that closures have the advantage that I can call it without having to identify all of the parameters by name. And (though I haven't tested it), another closure advantage may be that it's definition may be dynamic and possibly changed at runtime.

But with these advantages of closures, what's a case where a function would have advantages over a closure?

Answered by Claude31 in 646569022

A closure let you write a func "in line", without having to define an external explicit func:

Code Block func backward(_ s1: String, _ s2: String) -> Bool {
    return s1 > s2
}
var reversedNames = names.sorted(by: backward)

can be replaced by more condensed

Code Block reversedNames = names.sorted(by: { (s1: String, s2: String) -> Bool in return s1 > s2 } )

Apple Inc. « The Swift Programming Language (Swift 4). » Apple Books.

But func and closures are very close.
You can name a closure

Code Block     let closure = { print("")}

But it is much easier to pass arguments through a func.

So, which is better depends on the context of the code.

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Answer 1

Claude31 OP

Nov ’20

Accepted Answer

A closure let you write a func "in line", without having to define an external explicit func:

Code Block func backward(_ s1: String, _ s2: String) -> Bool {
    return s1 > s2
}
var reversedNames = names.sorted(by: backward)

can be replaced by more condensed

Code Block reversedNames = names.sorted(by: { (s1: String, s2: String) -> Bool in return s1 > s2 } )

Apple Inc. « The Swift Programming Language (Swift 4). » Apple Books.

But func and closures are very close.
You can name a closure

Code Block     let closure = { print("")}

But it is much easier to pass arguments through a func.

So, which is better depends on the context of the code.

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