Implement Swift function with completion block outside parameter set

Question

As I understood right we can use function

func saveImage(imageType:imageType, thumb: UIImage, completion: CompletionHandler)

like this:

imageSaver.saveImage(someType, thumb:image) { in
...
}

but actually as from Objective-C I suppose that block is a parameter and maybe should I use it like this:

imageSaver.saveImage(someType, thumb:image, { in
...
})

Also one more that is interesting for me as Objective-C coder it's passing arguments to a function:

so if I want to add some params to savaImage function like this:

func saveImage(someInt:UInt, imageType:imageType, thumb: UIImage, completion: CompletionHandler)

then I should call it with specifying imageType name.

imageSaver.saveImage(10, imageType:someType, thumb:image) { in
...
}

I guess in Swift we have something like skipping definition of function

Objective-C example:

- (void)saveImage:(UIImage *)image withParams:(NSDictionary *)params

So withParams sometimes can be skipped at start of function, as I understood right, which is not quite obvious for me)

@PEEJWEEJ my question is it legal to implement block outside () of function, so as I see it's a last parameter of function. in objective c we did not use it like that. — Oleksandr Matrosov
– Oleksandr Matrosov, Commented Apr 18, 2016 at 16:16

GetSwifty · Accepted Answer · 2016-04-18 16:20:24Z

2

Yes that's part of the purpose of the distinction between a closure and a function. It's not really defining a block outside the function, so much as some syntactic sugar to improve readability.

I would suggest reading through this: Closure Documentation

answered Apr 18, 2016 at 16:20

GetSwifty

7,7761 gold badge32 silver badges46 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Oleksandr Matrosov Over a year ago

ok got it, but it means that it will work only in case if the closure is a last param in the function. right?

GetSwifty Over a year ago

I believe that's correct. It also doesn't work from within "if let" or "guard let" statements

Collectives™ on Stack Overflow

Implement Swift function with completion block outside parameter set

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related