在Swift中以Equatable和Printable作为参数的泛型函数和属性 [英] Generic function and attribute with Equatable and Printable as parameters in Swift

问题描述

如何编写一个允许任何对象但在Swift中必须为对象的Printable和Equatable数组的函数?

How to write a function that allow any objects but must be Printable and Equatable array of objects in Swift?

class func withItems(items: [AnyObject]){

}

1. 我需要将项目设置为Printable和Equatable
2. 我需要将items数组声明为类的属性

谢谢

推荐答案

您可以使用泛型约束在一个函数中同时要求两个协议:

You can use generic constraints to require both protocols in a function:

class func withItems<T: AnyObject where T: Equatable, T: Printable>(items: [T]) {
    // ...
}

因为Equatable不能用作类型，所以要求具有存储属性的操作比较棘手.为此，您实际上需要使类本身具有通用性.最好将items声明为AnyObject的数组，并通过像这样的通用方法提供对它的访问.

Requiring that of a stored property is trickier, since Equatable can't be used as a type. In order to do so you'd essentially need to make the class itself generic. You'd probably be better off declaring items as an array of AnyObject and providing access to it through generic methods like this one.

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