map function argument type

Question

Created Mar ’16

Replies 2

Boosts 0

Participants 3

Here's a little test function:

import UIKit

func foo() {
    let views1 = (1...2).map { _ in
        let v = UIView()
        return v
    }
    
    let views2 = (1...2).map { _ in
        return UIView()
    }
    
    
}

I would expect the two map calls to behave identically. In fact, view2 compiles fine; but I get this error on view1:

error: cannot invoke 'map' with an argument list of type '(@noescape (Int) throws -> _)'
let views1 = (1...2).map { _ in
                             ^
note: expected an argument list of type '(@noescape (Self.Generator.Element) throws -> T)'
let views1 = (1...2).map { _ in
                             ^

Can anyone tell me what is going on?

Thanks.

Boost

Answer 1

beyondstorm OP

Mar ’16

import UIKit

func foo() {

let views1: [UIView] = (1...2).map { _ in

let v = UIView()

return v

}

let views2 = (1...2).map { _ in

return UIView()

}

it's ok after setting view1 type explicitly, I guess the Swift compiler can't infer view1 type when you write codes like this: define a varible, then return it.

0

Answer 2

DTS Engineer OP

Apple

Mar ’16

Just FYI, Neil Faiman posted the same question to swift-users and got a bunch of interesting answers. The question is here and you can see the answers here (when you get there, keep clicking Next message to see more follow-up posts).

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0