更改枚举Swift的关联值 [英] Changing associated value of enum Swift

问题描述

如何更改枚举的特定关联值

 枚举Origin {
 case search（searchTerm：字符串，已过滤：Bool）
案例类别（categoryName：字符串，subcategoryName：String）
 
} 
 
 @objc类GameSession：NSObject 
 {
 var gameOrigin：起源？ 
 
 ... 
 
 @objc func setIsSearchFiltered（filtered：Bool）
 {
 if（< gameOrigin类型为.search？> ）
 {
 self.gameOrigin =<将已过滤的关联值更改为新值> 
} 
} 
 
 .... 
} 
  

这个有答案的问题，很遗憾，最近对我没有帮助。

解决方案

您只能分配该变量的新枚举值。
如我可以更改枚举的关联值？？
当前值的关联值可以在switch语句
中使用case样式将关联值绑定到局部变量。 p>

不需要当前关联的过滤的值，因此
我们可以使用通配符模式 _ 。

由于 var gameOrigin：Origin？是可选，我们需要带有尾随问号的可选模式。

  switch gameOrigin {
 case .search（让searchTerm，_）?： 
 gameOrigin = .search（searchTerm：searchTerm，已过滤：已过滤）
默认值：
 break 
} 
  

在具有情况和模式$ b $的if语句中，也可以这样做b匹配：

 如果是case.search（让searchTerm，_）？ = gameOrigin {
 gameOrigin = .search（searchTerm：searchTerm，已过滤：已过滤）
} 
  

How do I change a specific associated value of an enum

enum Origin {
    case search(searchTerm: String, filtered: Bool)
    case category(categoryName:String, subcategoryName:String)

}

@objc class GameSession: NSObject
{
    var gameOrigin: Origin?

    ...

    @objc func setIsSearchFiltered(filtered:Bool)
    {
        if (<gameOrigin is of type .search?>)
        {
            self.gameOrigin = <change "filtered" associated value to new value>
        }
    }

    ....
}

This question with answer, unfortunately, lately didn't help me.

解决方案

You can only assign a new enumeration value to the variable. As in Can I change the Associated values of a enum?, the associated values of the current values can be retrieved in a switch statement, with a case pattern which binds the associated value to a local variable.

The currently associated filtered value is not needed, therefore we can use a wildcard pattern _ at that position.

Since var gameOrigin: Origin? is an optional, we need an "optional pattern" with a trailing question mark.

switch gameOrigin {
case .search(let searchTerm, _)?:
    gameOrigin = .search(searchTerm: searchTerm, filtered: filtered)
default:
    break
}

The same can be done also in an if-statement with case and pattern matching:

if case .search(let searchTerm, _)? = gameOrigin {
    gameOrigin = .search(searchTerm: searchTerm, filtered: filtered)
}

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