Swift Dictionary的自定义序列 [英] Custom sequence for Swift Dictionary

问题描述

我有一个容器类，它有一个基础字典。我已经为这个类实现了下标来访问底层字典的成员。现在，我正在尝试在这个类上创建一个序列，这样我就可以通过在类实例本身上使用'for-in'循环来迭代底层字典的所有元素。我一直在寻找一些序列为Swift词典的例子，但找不到任何能很好地解释这些东西的东西。我已经看到了Swift数组的一些自定义序列示例，但没有看到Swift Dictionary的自定义序列示例。如果有人能解释我是如何实现这一点的，我真的很感激。以下是该类的代码（没有序列代码，因为我不知道从哪里开始）

I have a container class that has an underlying dictionary. I have implemented subscripts for this class to access member of the underlying dictionary. Now, I am trying to create a sequence on this class so that I could iterate over all the elements of the underlying dictionary by using 'for-in' loop on the class instance itself. I have been looking to find some examples for Sequences for Swift Dictionary but could not find anything that explains the stuff well. I have seen some custom sequence examples for Swift Array but none for the Swift Dictionary. I would really appreciate if anyone could explain how I can achieve that. Following is the code for the class (no sequence code yet as I am not sure where to begin)

import Foundation

class STCQuestionList : GeneratorType, SequenceType {

private var questionDict: [String : STCQuestion] = [ : ];

subscript(key : String?) -> STCQuestion? {
    get {
        if (key != nil) {
            return self.questionDict[key!];
        }
        return nil;
    }
    set(newValue) {
        if (key != nil) {
            self.questionDict[key!] = newValue;
        }
    }
}

func generate() -> GeneratorType {

}


 func next() -> (String, STCQuestion)? {
    if (self.questionDict.isEmpty) {
        return .None
    }

 }
}

推荐答案

如果我理解正确，那么转发生成怎么样？

If I'm understanding correctly, how about just forwarding on the generate?

func generate() -> DictionaryGenerator<String, STCQuestion> {
    return questionDict.generate()
}

（你不是需要实现 GeneratorType ，只需 SequenceType 就可以了。它是 generate（）本身返回 GeneratorType ， 必须实现的内容 next（），字典中现有的 generate（）实现已经为你做了。）

(You don't need to implement GeneratorType, just SequenceType should do. It's generate() itself that returns a GeneratorType, and that's what has to implement next(), which the existing generate() implementation in Dictionary already does for you.)

完整的工作示例根据您的代码：

Full worked example based on your code:

// Playground - noun: a place where people can play

import Foundation

class STCQuestion {
    let foo: String
    init(_ foo: String) {
        self.foo = foo
    }
}

class STCQuestionList : SequenceType {

    private var questionDict: [String : STCQuestion] = [ : ];

    subscript(key : String?) -> STCQuestion? {
        get {
            if key != nil {
                return self.questionDict[key!];
            }
            return nil;
        }
        set(newValue) {
            if key != nil {
                self.questionDict[key!] = newValue;
            }
        }
    }

    func generate() -> DictionaryGenerator<String, STCQuestion> {
        return questionDict.generate()
    }
}


var list = STCQuestionList()
list["test"] = STCQuestion("blah")
list["another"] = STCQuestion("wibble")
list["third"] = STCQuestion("doodah")

for (key, value) in list {
    println("Key: \(key) Foo: \(value.foo)")
}

// Output:
// Key: test Foo: blah
// Key: another Foo: wibble
// Key: third Foo: doodah

这篇关于Swift Dictionary的自定义序列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！