xcode $0 在 Swift 的闭包中代表什么？
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What does $0 represent in closures in Swift?
提问by lostAtSeaJoshua
I have seen closures in swift have $0 inside of it and sometimes they use $1. What exactly is $0 and what are other $x can you use?
我看到 swift 中的闭包里面有 $0，有时他们使用 $1。到底什么是 $0，还有什么是你可以使用的 $x？
Here are examples of it in use.
以下是它的使用示例。
applyMutliplication(2, {##代码## * 3})
array.map({##代码## + 1})
Thanks!
谢谢！
采纳答案by Andy Obusek
It's a shorthand argument name.
这是一个速记参数名称。
From the Swift Book:
来自斯威夫特书：
“Swift automatically provides shorthand argument names to inline closures, which can be used to refer to the values of the closure's arguments by the names $0, $1, $2, and so on.”
— Apple Inc. “The Swift Programming Language.”
“Swift 自动为内联闭包提供速记参数名称，可用于通过名称 $0、$1、$2 等引用闭包参数的值。”
— Apple Inc. “Swift 编程语言”。
It helps reduce the verbosity of your code (sometimes at the cost of readability), so you don't have to write out long argument lists when defining closures.
它有助于减少代码的冗长（有时以可读性为代价），因此您不必在定义闭包时写出很长的参数列表。
