Question

我声明并初始化了一个[[String:[String:String]字典。它在开头是空的，我试图在父键下添加多个值。

var dictionary = [String:[String:String]

// some checks

dictionary[i] = ["name" : name]
dictionary[i] = ["from" : country]
dictionary[i] = ["age" : age]

当我这样做时，我最终只有[key: [String:String]下的孩子年龄。所以当我使用这种方法时它会被覆盖。

适当的做法是什么

Answer 1

您的代码正在每行创建一个新词典，并在dictionary中为键i分配，因此您最终会得到最后一个词典["age" : age]

您需要创建一个内部字典，为其指定值，然后将其分配给外部字典;

var innerDict = [String:String]()
innerDict["name"] = name
innerDict["from"] = from
innerDict["age"] = age

dictionary[i] = innerDict

但是，我建议您考虑创建一个Struct并将其放在外部字典中而不是使用字典字典

Answer 2

func insert(key:String, value:String, at k:String) {
    var d = dictionary[k] ?? [String:String]()
    d[key] = value
    dictionary[k] = d
}

以下是如何测试它：

insert("name", value: name, at: i)
insert("from", value: country, at: i)
insert("age", value: age, at: i)

Answer 3

您可以使用可选链接分配到内部字典，但您需要先创建内部字典。

// create the dictionary of dictionaries
var dictionary = [String:[String:String]]()

// some example constants to make your code work    
let i = "abc"
let name = "Fred"
let country = "USA"
let age = "28"

// Use nil coalescing operator ?? to create    
// dictionary[i] if it doesn't already exist
dictionary[i] = dictionary[i] ?? [:]

// Use optional chaining to assign to inner dictionary
dictionary[i]?["name"] = name
dictionary[i]?["from"] = country
dictionary[i]?["age"] = age

print(dictionary)

输出：

["abc": ["age": "28", "from": "USA", "name": "Fred"]]

使用这些技巧，这是我的@ matt insert(_:value:at:)函数的版本：

func insert(key:String, value:String, at k:String) {
    dictionary[k] = dictionary[k] ?? [:]
    dictionary[k]?[key] = value
}

在多维字典中添加“键：值”会覆盖

3 个答案: