ios - Swift - 闭包模式

Question

我正在阅读有关 Swinject 的文档，但我不明白这段代码中的两件事:

let container = Container()
container.register(AnimalType.self) { _ in Cat(name: "Mimi") }
container.register(PersonType.self) { r in
    PetOwner(pet: r.resolve(AnimalType.self)!)
}

两个闭包如何独立存在而不嵌入方法调用中？闭包没有返回任何对象，我没有看到任何“返回”。那么容器如何获得“Cat”实例呢？ (还有 PetOwner 实例)。

谢谢

Answer 1

1. “两个闭包是独立的，没有嵌入到方法调用中”

这就是所谓的“尾随闭包”:

If you need to pass a closure expression to a function as the function’s final argument and the closure expression is long, it can be useful to write it as a trailing closure instead. A trailing closure is a closure expression that is written outside of (and after) the parentheses of the function call it supports...

来源:Apple's documentation

1. “闭包没有返回任何对象，我没有看到任何‘返回’”

该功能称为“隐式返回”:

Single-expression closures can implicitly return the result of their single expression by omitting the return keyword from their declaration...

来源:Apple's documentation