在 Swift 中使用字符串变量的值引用对象

Question

在我下面的代码中，我无法获取 performActivity 方法来增加角色的快乐度。因为 'need' 作为字符串出现，值为 "happiness" 而我需要对 "happiness" 进行更改，这是一个 class 实例。如果有任何帮助，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each需要一个对象，让eachactivity直接修改。这里不需要（或不需要）字符串。如果将效果存储为 DictionaryLiteral 而不是 Dictionary，使用它也会更容易一些。这样我们就不需要经历使需求可哈希化的麻烦。

// 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
}

在 Swift 中使用字符串变量的值引用对象

Referring to an object using a string variable's value in Swift

methods

swift

swift3

ios10