是否可以指定字典中允许的对象类型？ [英] Is it possible to specify the object type allowed in a Dictionary?

问题描述

在Swift 3.x中可以指定字典中允许的对象类型吗？

In Swift 3.x is it possible to specify the object type allowed in a Dictionary?

如果在声明时我们可以传递一组

It would be great if at declaration time we could pass a set of object types allowed.

推荐答案

您可以通过自定义协议来实现此目的，该协议仅由要允许的对象类型实现。字典：

You can achieve this via a custom protocol that is implemented only by the types you want to allow within the dictionary:

protocol AllowedDictionaryValue: {}

extension String: AllowedDictionaryValue {}
extension Int: AllowedDictionaryValue {}
extension MyClass: AllowedDictionaryValue {}
extension MyEnum: AllowedDictionaryValue {}

let dictionary: [String:AllowedDictionaryValue] = ...

以上字典仅包含 String ， Int ， MyClass 实例和 MyEnum 值。

The above dictionary will hold only String's, Int's, MyClass instances, and MyEnum values.

这样，您可以在字典中只保留想要的值，同时保持字典的异构性。

This way you can have only the values you want in the dictionary, while keeping the dictionary heterogenous.

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