ios - 在swift中遍历nsdictionary

Question

我是 swift 的新手。 我的字典是

monthData = 
{
    "2018-08-10" = {
        accuracy = 71;
        attempted = 7;
        correct = 5;
        reward = Bronze;
    };
    "2018-08-12" = {
        accuracy = 13;
        attempted = 15;
        correct = 2;
        reward = "";
    };
    "2018-08-13" = {
        accuracy = 33;
        attempted = 15;
        correct = 5;
        reward = "";
    };
    "2018-08-14" = {
        accuracy = 100;
        attempted = 15;
        correct = 15;
        reward = Gold;
    };
    "2018-08-16" = {
        accuracy = 73;
        attempted = 15;
        correct = 11;
        reward = Silver;
    };
    "2018-08-21" = {
        accuracy = 26;
        attempted = 15;
        correct = 4;
        reward = "";
    };
    "2018-08-23" = {
        accuracy = 46;
        attempted = 15;
        correct = 7;
        reward = "";
    };
}

我想获取所有 reward 为 Gold 的日期

有人可以帮我做吗？

到目前为止，我尝试过的是:

for (key,value) in monthData{
   let temp = monthData.value(forKey: key as! String) as! NSDictionary
   for (key1,value1) in temp{
     if((value1 as! String) == "Gold"){
       print("keyFINAL \(key)")
     }
}

但它输出错误 Could not cast value of type '__NSCFNumber' to 'NSString'

Answer 1

发生错误是因为当您迭代字典时，您强制将 Int 值转换为 String，这是不可能的

(高度)推荐的 Swift 方法是使用 filter 函数。这比循环更有效。

在闭包中，$0.1 表示当前字典的值($0.0 将是键)。结果是一个日期字符串数组。

let data : [String:Any] = ["monthData" : ["2018-08-10": ["accuracy" : 71, "attempted" ... ]]]

if let monthData = data["monthData"] as? [String:[String:Any]] {
    let goldData = monthData.filter { $0.1["reward"] as? String == "Gold" }
    let allDates = Array(goldData.keys)
    print(allDates)
}

代码安全地解包所有可选值。

但是，如果只有一个 Gold 条目，first 函数仍然比filter

更有效

if let monthData = data["monthData"] as? [String:[String : Any]] {
    if let goldData = monthData.first( where: {$0.1["reward"] as? String == "Gold" }) {
       let goldDate = goldData.key
        print(goldDate)
    }
}

在 Swift 中，尽可能避免使用 ObjC 运行时 (value(forKey:)) 和 Foundation 集合类型 (NSDictionary)。