如何在 Swift 中组合两个 Dictionary 实例？

Question

如何使用Swift 将一个Dictionary 附加到另一个Dictionary？

我正在使用AlamoFire 库将JSON 发送到REST server。

字典 1

var dict1: [String: AnyObject] = [
    kFacebook: [
        kToken: token
    ]
]

字典 2

var dict2: [String: AnyObject] = [
    kRequest: [
        kTargetUserId: userId
    ]
]

如何将两个字典组合成一个新字典，如下图所示？

let parameters: [String: AnyObject] = [
    kFacebook: [
        kToken: token
    ],
    kRequest: [
        kTargetUserId: userId
    ]
]

我尝试过dict1 += dict2，但出现编译错误：

二元运算符“+=”不能应用于两个“[String : AnyObject]”操作数

Answer 1

我喜欢这种方法：

dicFrom.forEach { (key, value) in dicTo[key] = value }

Swift 4 和 5

随着 Swift 4，Apple 引入了一种更好的方法来合并两个字典：

let dictionary = ["a": 1, "b": 2]
let newKeyValues = ["a": 3, "b": 4]

let keepingCurrent = dictionary.merging(newKeyValues) { (current, _) in current }
// ["b": 2, "a": 1]

let replacingCurrent = dictionary.merging(newKeyValues) { (_, new) in new }
// ["b": 4, "a": 3]

这里有 2 个选项（与大多数在容器上运行的函数一样）：

• merge 改变现有字典
• merging 返回一个新字典

Answer 2

var d1 = ["a": "b"]
var d2 = ["c": "e"]

extension Dictionary {
    mutating func merge(dict: [Key: Value]){
        for (k, v) in dict {
            updateValue(v, forKey: k)
        }
    }
}

d1.merge(d2)

参考很棒的美元和美分项目 https://github.com/ankurp/Cent/blob/master/Sources/Dictionary.swift

Answer 3

对于 Swift >= 2.2：
let parameters = dict1.reduce(dict2) { r, e in var r = r; r[e.0] = e.1; return r }

对于 Swift let parameters = dict1.reduce(dict2) { (var r, e) in r[e.0] = e.1; return r }

Swift 4 有一个新功能： let parameters = dict1.reduce(into: dict2) { (r, e) in r[e.0] = e.1 }

挖掘标准库非常重要：map、reduce、dropFirst、forEach 等是简洁代码的主要内容。功能位很有趣！

Answer 4

我们可以使用merge关键字更好地合并字典

var dictionary = ["a": 1, "b": 2]
/// Keeping existing value for key "a":
dictionary.merge(["a": 3, "c": 4]) { (current, _) in current }
 // ["b": 2, "a": 1, "c": 4]

Answer 5

extension Dictionary {
    static func +=(lhs: inout Self, rhs: Self) {
        lhs.merge(rhs) { _ , new in new }
    }
    static func +=<S: Sequence>(lhs: inout Self, rhs: S) where S.Element == (Key, Value) {
        lhs.merge(rhs) { _ , new in new }
    }
}

---

var dic = ["test1": 1]
dic += ["test2": 2]
dic  // ["test1": 1, "test2": 2]
dic += [("test2", 3),("test3", 4)]
dic  // ["test3": 4, "test1": 1, "test2": 3]

Answer 6

SequenceType.forEach（由Dictionary 实现）提供了一种优雅的解决方案，可以将字典的元素添加到另一个字典。

dic1.forEach { dic2[$0] = $1 }

例如

func testMergeDictionaries() {
    let dic1 = [1:"foo"]
    var dic2 = [2:"bar"]

    dic1.forEach { dic2[$0] = $1 }

    XCTAssertEqual(dic2[1], "foo")
}

Answer 7

我的需求不同，我想合并而不是破坏。

merging:
    ["b": [1, 2], "s": Set([5, 6]), "a": 1, "d": ["x": 2]]
with
    ["b": [3, 4], "s": Set([6, 7]), "a": 2, "d": ["y": 4]]
yields:
    ["b": [1, 2, 3, 4], "s": Set([5, 6, 7]), "a": 2, "d": ["y": 4, "x": 2]]

我希望有一个更简单的解决方案，但这就是我最终得到的。挑战在于从动态类型转换到静态类型，我使用协议来解决这个问题。

另外值得注意的是，当您使用字典字面量语法时，您实际上获得了基础类型，它不采用协议扩展。我放弃了支持这些的努力，因为我找不到一个简单的方法来验证集合元素的一致性。

import UIKit


private protocol Mergable {
    func mergeWithSame<T>(right: T) -> T?
}



public extension Dictionary {

    /**
    Merge Dictionaries

    - Parameter left: Dictionary to update
    - Parameter right:  Source dictionary with values to be merged

    - Returns: Merged dictionay
    */


    func merge(right:Dictionary) -> Dictionary {
        var merged = self
        for (k, rv) in right {

            // case of existing left value
            if let lv = self[k] {

                if let lv = lv as? Mergable where lv.dynamicType == rv.dynamicType {
                    let m = lv.mergeWithSame(rv)
                    merged[k] = m
                }

                else if lv is Mergable {
                    assert(false, "Expected common type for matching keys!")
                }

                else if !(lv is Mergable), let _ = lv as? NSArray {
                    assert(false, "Dictionary literals use incompatible Foundation Types")
                }

                else if !(lv is Mergable), let _ = lv as? NSDictionary {
                    assert(false, "Dictionary literals use incompatible Foundation Types")
                }

                else {
                    merged[k] = rv
                }
            }

                // case of no existing value
            else {
                merged[k] = rv
            }
        }

        return merged
    }
}




extension Array: Mergable {

    func mergeWithSame<T>(right: T) -> T? {

        if let right = right as? Array {
            return (self + right) as? T
        }

        assert(false)
        return nil
    }
}


extension Dictionary: Mergable {

    func mergeWithSame<T>(right: T) -> T? {

        if let right = right as? Dictionary {
            return self.merge(right) as? T
        }

        assert(false)
        return nil
    }
}


extension Set: Mergable {

    func mergeWithSame<T>(right: T) -> T? {

        if let right = right as? Set {
            return self.union(right) as? T
        }

        assert(false)
        return nil
    }
}



var dsa12 = Dictionary<String, Any>()
dsa12["a"] = 1
dsa12["b"] = [1, 2]
dsa12["s"] = Set([5, 6])
dsa12["d"] = ["c":5, "x": 2]


var dsa34 = Dictionary<String, Any>()
dsa34["a"] = 2
dsa34["b"] = [3, 4]
dsa34["s"] = Set([6, 7])
dsa34["d"] = ["c":-5, "y": 4]


//let dsa2 = ["a": 1, "b":a34]
let mdsa3 = dsa12.merge(dsa34)
print("merging:\n\t\(dsa12)\nwith\n\t\(dsa34) \nyields: \n\t\(mdsa3)")

Answer 8

试试这个方法

    let dict1: [String: AnyObject] = ["kFacebook": ["kToken": "token"]]
    let dict2: [String: AnyObject] = ["kRequest": ["kTargetUserId": "userId"]]

    var combinedAttributes : NSMutableDictionary!

    combinedAttributes = NSMutableDictionary(dictionary: dict1)

    combinedAttributes.addEntriesFromDictionary(dict2)

    println(combinedAttributes)

它将打印以下内容：

{
kFacebook =     {
    kToken = token;
};
kRequest =     {
    kTargetUserId = userId;
};

}

希望对你有帮助！！

Answer 9

您可以使用以下代码在 Swift 中组合两个字典实例：

extension Dictionary {
    func merge(dict: Dictionary<Key,Value>) -> Dictionary<Key,Value> {
        var mutableCopy = self
        for (key, value) in dict {
            // If both dictionaries have a value for same key, the value of the other dictionary is used.
            mutableCopy[key] = value
        }
        return mutableCopy
    }
}

Answer 10

您正在使用 let 关键字来声明字典，因此您不能对字典进行更改，因为它用于声明常量。

将其更改为 var 关键字，然后它将为您工作。

var dict1: [String: AnyObject] = [
            kFacebook: [
                kToken: token
            ]
        ]

var dict2: [String: AnyObject] = [
        kRequest: [
            kTargetUserId: userId
        ]
    ]

dict1 += dict2