从字典中删除嵌套的键 [英] Remove nested key from dictionary

问题描述

假设我有一个相当复杂的字典，就像这样：

  let dict：[String：Any] = [ 
countries：[
japan：[
capital：[
name：tokyo，
lat：35.6895 ，
lon：139.6917
]，
language：japanese
] 
]，
 b $ bgermany：[FRA，MUC，HAM，TXL] 
] 
] 
  

我可以使用访问所有字段，如果let .. 阻止可以转换为可以使用的东西，当阅读时。

但是，我正在编写单元测试，我需要以多种方式有选择地打破字典。

但我不知道如何从字典中优雅地删除密钥。

例如我想在一个测试中删除密钥japan，下一个lat应该为零。

这是我目前的删除lat的实现：

 如果var countries = dict [countries] as？ [String：Any]，
 var japan = countries [japan] as？ [String：Any]，
 var capital = japan [capital] as？ [String：Any] 
 {
 capital.removeValue（forKey：lat）
 japan [capital] = capital 
 countries [japan] = japan 
 dictWithoutLat [countries] = countries 
} 
  

当然必须有更多优雅的方式？

理想情况下，我会写一个测试帮手，需要一个KVC字符串，并具有如下的签名：

  func dictWithoutKeyPath（_ path：String） - > [String：Any] 
  

在lat case我会称之为 dictWithoutKeyPath（countries.japan.capital.lat）。

解决方案

当使用下标时，如果下标是get / set，变量是可变的，则整个表达式是可变的。然而，由于类型转换，表达式失去可变性。 （这不再是 l值）。

解决这个问题的最短的方法是创建一个下标，这个下标是get / set，并为您进行转换。

 扩展字典{
 subscript（jsonDict key：Key） - > [字符串：任何]？ {
 get {
 return self [key] as？ [String：Any] 
} 
 set {
 self [key] = newValue as？价值
} 
} 
} 
  

现在你可以写以下：

  dict [jsonDict：countries]？[jsonDict：japan]？[jsonDict：capital] ？[name] =berlin
  

我们很喜欢这个问题，关于它的（公开）Swift Talk插曲：突变无类型字典

Let's say I have a rather complex dictionary, like this one:

let dict: [String: Any] = [
    "countries": [
        "japan": [
            "capital": [
                "name": "tokyo",
                "lat": "35.6895",
                "lon": "139.6917"
            ],
            "language": "japanese"
        ]
    ],
    "airports": [
        "germany": ["FRA", "MUC", "HAM", "TXL"]
    ]
]

I can access all fields with if let .. blocks optionally casting to something that I can work with, when reading.

However, I am currently writing unit tests where I need to selectively break dictionaries in multiple ways.

But I don't know how to elegantly remove keys from the dictionary.

For example I want to remove the key "japan" in one test, in the next "lat" should be nil.

Here's my current implementation for removing "lat":

if var countries = dict["countries"] as? [String: Any],
    var japan = countries["japan"] as? [String: Any],
    var capital = japan["capital"] as? [String: Any]
    {
        capital.removeValue(forKey: "lat")
        japan["capital"] = capital
        countries["japan"] = japan
        dictWithoutLat["countries"] = countries
}

Surely there must be a more elegant way?

Ideally I'd write a test helper that takes a KVC string and has a signature like:

func dictWithoutKeyPath(_ path: String) -> [String: Any] 

In the "lat" case I'd call it with dictWithoutKeyPath("countries.japan.capital.lat").

解决方案

When working with a subscript, if the subscript is get/set and the variable is mutable, then the entire expression is mutable. However, due to the type cast the expression "loses" the mutability. (It's not an l-value anymore).

The shortest way to solve this is by creating a subscript that is get/set and does the conversion for you.

extension Dictionary {
    subscript(jsonDict key: Key) -> [String:Any]? {
        get {
            return self[key] as? [String:Any]
        }
        set {
            self[key] = newValue as? Value
        }
    }
}

Now you can write the following:

dict[jsonDict: "countries"]?[jsonDict: "japan"]?[jsonDict: "capital"]?["name"] = "berlin"

We liked this question so much that we decided to make a (public) Swift Talk episode about it: mutating untyped dictionaries

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