Xcode 为什么swift 3在闭包参数中需要``？

我是swift 3的新手。我有现有的代码，想把它转换成swift 3。我只是好奇为什么xcode要求我在参数名之前插入

。

func anotherClosure(age: Int, name: String, handler: (_ name: String, _ age: Int) -> ()) {
        handler(name, age)
    }

我正在网上搜索，但找不到答案。如果您有更好的方法创建具有多个值的闭包，并将其传递给处理程序，请在下面进行评论

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感谢在Swift 3之前，就类型系统而言，参数名称是类型的一部分。然而，强制使关键字名称正确匹配将使使用闭包成为一场噩梦。因此，类型系统忽略了它们，这就引出了一个问题：为什么它们在名字中是类型的一部分

import CoreFoundation

func applyAndPrint(closure: (a: Double, b: Double) -> Double, _ a: Double, _ b: Double) {
    print(a, b, closure(a: a, b: b))
}

//All these have different types, because of their different keyword parameter names.
let adder: (augend: Double, addend: Double) -> Double = { $0 + $1 }
let subtractor: (minuend: Double, subtrahend: Double) -> Double = { $0 - $1 }
let multiplier: (multiplicand: Double, multiplier: Double) -> Double = { $0 * $1 }
let divider: (dividend: Double, divisor: Double) -> Double = { $0 / $1 }
let exponentiator: (base: Double, exponent: Double) -> Double = { pow($0, $1) }
let rooter: (degree: Double, Radicand: Double) -> Double = { pow($1, 1/$0) }

// Yet the type system ignores that, and all these are valid:
applyAndPrint(adder, 2, 3)
applyAndPrint(subtractor, 2, 3)
applyAndPrint(multiplier, 2, 3)
applyAndPrint(divider, 2, 3)
applyAndPrint(exponentiator, 2, 3)
applyAndPrint(rooter, 2, 3)

---

在Swift 3之前，就类型系统而言，参数名称是类型的一部分。然而，强制使关键字名称正确匹配将使使用闭包成为一场噩梦。因此，类型系统忽略了它们，这就引出了一个问题：为什么它们在名字中是类型的一部分

import CoreFoundation

func applyAndPrint(closure: (a: Double, b: Double) -> Double, _ a: Double, _ b: Double) {
    print(a, b, closure(a: a, b: b))
}

//All these have different types, because of their different keyword parameter names.
let adder: (augend: Double, addend: Double) -> Double = { $0 + $1 }
let subtractor: (minuend: Double, subtrahend: Double) -> Double = { $0 - $1 }
let multiplier: (multiplicand: Double, multiplier: Double) -> Double = { $0 * $1 }
let divider: (dividend: Double, divisor: Double) -> Double = { $0 / $1 }
let exponentiator: (base: Double, exponent: Double) -> Double = { pow($0, $1) }
let rooter: (degree: Double, Radicand: Double) -> Double = { pow($1, 1/$0) }

// Yet the type system ignores that, and all these are valid:
applyAndPrint(adder, 2, 3)
applyAndPrint(subtractor, 2, 3)
applyAndPrint(multiplier, 2, 3)
applyAndPrint(divider, 2, 3)
applyAndPrint(exponentiator, 2, 3)
applyAndPrint(rooter, 2, 3)