在 Swift 中使用字符串变量的值引用对象

Question

在下面的代码中，我无法使用 performActivity 方法来增加角色的幸福感。因为 'need' 以字符串的形式出现，其值为“happiness”，而我需要对作为类实例的“happiness”进行更改。如有任何帮助，我将不胜感激！

// Character Needs Class
class CharNeeds {
    var currentNeedValue : Int = 0

    func changeNeedValue (changeBy : Int){
        currentNeedValue += changeBy
    }


}

// Activities Class

class Activities{
    let activityName : String
    var effects = [String: Int]()

    //Initializers
    init(activityName: String, effects: [String: Int]){
        self.activityName = "Unnamed Activity"
        self.effects = effects
    }

    //Methods
    static func performActivity(activityName : Activities){

        for (need, effect) in activityName.effects {
            need.changeNeedValue(changeBy: effect)
        }
    }
}

//Testing

var happiness = CharNeeds()
var cycling = Activities(activityName: "cycling", effects: ["happiness":10])
Activities.performActivity(activityName: cycling)

Answer 1

这种设计在某些方面是倒退的。让每个需要一个对象，并让每个活动直接修改它。这里不需要（或渴望）字符串。如果您将效果存储为DictionaryLiteral 而不是Dictionary，那么使用它也会更容易一些。这样我们就不需要费力地将需求设为 Hashable。

// A need has an immutable name and a mutable value that can be increased and read
class Need {
    let name: String
    private(set) var value = 0

    init(name: String) {
        self.name = name
    }

    func increaseValue(by: Int){
        value += by
    }
}

// An Activity has an immutable name and an immutable list of needs and adjustments
class Activity {
    let name: String
    let effects: DictionaryLiteral<Need, Int>

    init(name: String, effects: DictionaryLiteral<Need, Int>){
        self.name = name
        self.effects = effects
    }

    func perform() {
        for (need, effect) in effects {
            need.increaseValue(by: effect)
        }
    }
}

// Now we can assign happiness to this activity, and perform it.
let happiness = Need(name: "happiness")
let cycling = Activity(name: "cycling", effects: [happiness: 10])
cycling.perform()
happiness.value

如果您收到字符串，那么您只需要保留字符串到需求的映射。例如：

let needMap = ["happiness": Need(name: "happiness")]
if let happiness = needMap["happiness"] {
    let cycling = Activity(name: "cycling", effects: [happiness: 10])
    cycling.perform()
    happiness.value
}