Simple closures

We will begin by creating a very simple closure that does not accept any arguments and does not return any value. All it does is print Hello World to the console. Let's take a look at the following code:

let clos1 = {
  () -> Void in
  
  println("Hello World")
}

In this example, we create a closure and assign it to the constant clos1. Since, there are no parameters defined between the parentheses, this closure will not accept any parameters. Since, the return type is defined as Void, this closure will also not return any value. The body of the closure contains one line that simply prints Hello World to the console.

There are many ways to use closures; in this example, all we want to do is call it. We can execute this closure like this:

clos1()

When we execute the closure, we will see Hello World printed to the console. At this point, closures may not seem that useful, but as we get further along in this chapter, we will see how useful and powerful closures can be.

Let's look...