Swift:函数与闭包的定义和语法

Question

这是一个函数还是一个闭包？

let triple: Int -> Int = {
    (number: Int) in // What is this?
    let result = 3 * number
    number
    return result
}

triple(1)

Answer 1

1:这是一个闭包。

例子:

func aFunction() -> () {
    // do something
}

let aClosure:() -> () = {
    // do something
}

Functions are actually a special case of closures. You can write a closure without a name by surrounding code with braces ({}). Use in to separate the arguments and return type from the body.

摘自:Apple Inc.“The Swift Programming Language”。电子书。 https://itun.es/us/jEUH0.l

2:“in”只是选择的符号来表示参数/返回类型结束的位置，以及闭包主体的开始位置。与inout无关。