What are Closures in Swift 3? (Part 2)

In the last post I wrote about what closures are and some use of them now I want to cover about some important characteristics of closures and these are:

• Inferring Type from Context
• Implicit Return from Single-Expression Closures

Let’s tackle one at a time.

Inferring Type from Context

We have this function:

sayHello method accepts a String and a Closure on its parameters and we call it in this way:

But since it is already known that the type expected of the Closure argument will be (String) -> Void, we could only remove the types of the argument and the type of return like this:

You see the difference? We removed the type String of person and also the returning type it happens to be Void.

Implicit Return from Single-Expression Closures

In the following code I’m filtering the zeros from the array.

Swift allows us to remove the keyword return when we have a single expression like in the example above, we’re only doing a single thing that’s returning something.

And Swift already knows that the returning type of the closure will be a Bool, filter method expects a Closure like (Int) -> Bool, and the call is reduced like this:

Hope you find it useful this quick view of Closures so there will be a last post about some other characteristics of Closures that I saw are important but I will reserve that for another post.

Thanks for reading me!