Duncan Rowland - 1 month ago 10

Swift Question

I am trying to understand closures in swift and am missing something fundamental.

Given the following example:

`var numbers = [20, 19, 7, 12]`

numbers.map({(number: Int) -> Int in return 3 * number})

numbers.map {(number: Int) -> Int in return 3 * number}

numbers.sorted {(n1:Int, n2:Int) -> Bool in return n1 < n2}

Why do the extra braces work for map but not sorted?

i.e.

`numbers.sorted({(n1:Int, n2:Int) -> Bool in return n1 < n2})`

does not compile...

`"error: argument passed to call that takes no arguments"`

Please could someone could explain the difference? Thanks.

Answer

Because sort method is func sorted(by:). So you have to add ** by**
param name:

```
numbers.sorted(by: {(n1:Int, n2:Int) -> Bool in return n1 < n2})
```