flatMap --斯威夫特词典词典

Question

我有一个NSEnumerator，它包含嵌套的键值对象，如下所示：

 [ "posts" :
    ["randonRootKey1" :
        ["randomChildKey1" : [:] ]
    ], 
    ["randonRootKey2" :
        ["randomChildKey2" : [:] ],
        ["randomChildKey3" : [:] ],
    ]  
]

- posts
-- user1
--- posts
----post
-- user2
-- posts
--- post 

我想在一个数组中提取所有用户的所有帖子.最后一个孩子和所有的父母都是字典

我想flatMap它是：

[
        ["randomChildKey1" : [:] ],
        ["randomChildKey2" : [:] ],
        ["randomChildKey3" : [:] ]
]

注意，我已经提取了每个根字典的对象。

我试过：

let sub = snapshot.children.flatMap({$0}) 

但似乎不起作用

Answer 1

 let input: [String: [String: [String: Any]]] = ["posts":
    [
        "randonRootKey1": [
            "randomChildKey1": [:],
        ],
        "randonRootKey2": [
            "randomChildKey2": [:],
            "randomChildKey3": [:],
        ]
    ]
]

var output = [String: Any]()

for dictionary in input["posts"]!.values {
    for (key, value) in dictionary {
        output[key] = value
    }
}

print(output)

["randomChildKey3"："randomChildKey2"："randomChildKey1"：]

Answer 2

假设输入为此格式

let input: [String: [String: [String: Any]]] = ["posts":
    [
        "randonRootKey1": [
            "randomChildKey1": [:],
        ],
        "randonRootKey2": [
            "randomChildKey2": [:],
            "randomChildKey3": [:],
        ]
    ]
]

用这个

let output = input.flatMap{$0.1}.flatMap{$0.1}

您将获得所需的输出

[("randomChildKey1"，)，("randomChildKey2"，)，("randomChildKey3“)]

如果要将元组转换为字典，请使用reduce

let output = input.flatMap{$0.1}.flatMap{$0.1}.reduce([String: Any]())
{
    (var dict, tuple) in
    dict.append([tuple.0: tuple.1])
    return dict
}

["randomChildKey1"：{}，"randomChildKey2"：{}，"randomChildKey3"：{}]