用于字符串插值的 Swift 协议 [英] Swift protocol for string interpolation

问题描述

我必须实现什么协议来控制对象在 Swift 中的字符串插值中的表示方式?

What protocol do I have to implement to control the way an object is represented within a string interpolation in Swift?

我不想指定像这样打印的内容:

I wan't to specify what get's printed in something like this:

struct A{

}

var a = A()
println("\(a)")

推荐答案

你需要实现Printable协议:

希望自定义其的类型应采用此协议文字表示.这种文本表示用于对象被写入 OutputStreamType.

This protocol should be adopted by types that wish to customize their textual representation. This textual representation is used when objects are written to an OutputStreamType.

protocol Printable {
    var description: String { get }
}

还有 DebugPrintable 协议仅用于调试目的:

There's also the DebugPrintable protocol when it's only for debugging purposes:

希望自定义的类型应采用此协议它们用于调试目的的文本表示.这将对象写入到文本中时使用文本表示OutputStreamType.

This protocol should be adopted by types that wish to customize their textual representation used for debugging purposes. This textual representation is used when objects are written to an OutputStreamType.

protocol DebugPrintable {
    var debugDescription: String { get }
}

文档(感谢@MartinR)

Documentation (Thanks @MartinR)

注意:正如评论中提到的@Antonio 和@MartinR，这在操场上不起作用(无论如何从Xcode6 GM 开始)；这是一个已知的错误.它确实适用于已编译的应用程序.

Note: As @Antonio and @MartinR mentioned in the comments, this doesn't work in the playground (as of Xcode6 GM anyway); that's a known bug. It does work in compiled apps.

来自 Xcode6 GM 发行说明:

From the Xcode6 GM Release Notes:

在 Playgrounds 中，println() 忽略了 Printable 一致性用户定义的类型.(16562388)

In Playgrounds, println() ignores the Printable conformance of user-defined types. (16562388)

从 Swift 2.0 开始，Printable 现在变成了 CustomStringConvertible.一切都和以前一样，你仍然需要实现

As of Swift 2.0 Printable has now become CustomStringConvertible. Everything stays the same as before, you still need to implement

 var description: String { get }

但现在它被称为 CustomStringConvertible.并且调试是 CustomDebugStringConvertible

But now its called CustomStringConvertible. And debug is CustomDebugStringConvertible

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