在Swift 3中通过闭包定义常量有什么好处

Question

let a: UIView = {
    let a = UIView()
    a.frame = CGRect(x: 0, y: 0, width: 20, height: 20)
    return a
}()

I saw a lot of people's Swift source code defining let as this way. I just curious what is the benefit of this way?

Answer 1

In this case, there is no benefit, but if the variable in question were a value type then the benefit would be that you could perform some mutating setup code and still get a constant out of it.

It also lets you hide temporary variables that were only needed to initialize the constant, since they'll only exist inside the closure's scope.