在Swift中有多个类型的变量 [英] Have a variable with multiple types in Swift

问题描述

我想要一个变量，它可以有多种类型(我定义的只有一种)，例如:

I would like to have a variable, which can have multiple types (only ones, I defined), like:

var example: String, Int = 0
example = "hi"

此变量应该只能容纳Int和String类型的值.

This variable should be able to hold only values of type Int and String.

这可能吗?

感谢您的帮助；)

推荐答案

这是实现它的方法.完全按照您的期望工作.

protocol StringOrInt { }

extension Int: StringOrInt { }
extension String: StringOrInt { }

var a: StringOrInt = "10"
a = 10 //> 10
a = "q" //> "q"
a = 0.8 //> Error

注意！我不建议您在生产代码中使用它.这可能会使您的队友感到困惑.

NB! I would not suggest you to use it in production code. It might be confusing for your teammates.

UPD:，如@Martin R所述:请注意，这仅按惯例"限制了可能的类型.任何模块(或源文件)都可以添加扩展名MyType:StringOrInt {} 一致性.

UPD: as @Martin R mentioned: Note that this restricts the possible types only "by convention." Any module (or source file) can add a extension MyType: StringOrInt { } conformance.

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