我有这一系列字典：
var dicts = [["key1": "value1", "key2": "value2"], ["key1": "value3", "key2": "value4"]]
我应该如何延长Array这样我就有这个功能：
dicts.values(of: "key1") // result: ["value1", "value3"]
我试试这个：
extension Array where Iterator.Element == [String: Any] { // ERROR!
func values(of key: String) -> [Any]? {
var result: [Any]?
for value in self {
let val = value as! Dictionary<String, Any>
for k in val.keys {
if k == key {
if result == nil {
result = [Any]()
}
result?.append(val[k])
break
}
}
}
return result
}
}
但我总是有错误标记extension Array宣言：
错误：相同类型的要求使泛型参数“Element”成为非泛型
我应该怎么做才能修复这个错误？
迭代是否正确Array with for value in self?
Thanks
extension Sequence where Iterator.Element == [String: Any] {
func values(of key: String) -> [Any]? {
var result: [Any] = []
for value in self {
let val = value
for (k, v) in val {
if k == key {
result.append(v)
break
}
}
}
return result.isEmpty ? nil : result
}
}
var dicts: [[String: Any]] = [["key1": "value1", "key2": "value2"], ["key1": "value3", "key2": "value4"]]
dicts.values(of: "key1") // ["value1", "value3"]
或更短的版本：
extension Sequence where Iterator.Element == [String: Any] {
func values(of key: String) -> [Any]? {
let result: [Any] = reduce([]) { (result, dict) -> [Any] in
var result = result
result.append(dict.filter{ $0.key == key }.map{ $0.value })
return result
}
return result.isEmpty ? nil : result
}
}
var dicts: [[String: Any]] = [["key1": "value1", "key2": "value2"], ["key1": "value3", "key2": "value4"]]
dicts.values(of: "key1")
并且没有减少功能：
extension Sequence where Iterator.Element == [String: Any] {
func values(of key: String) -> [Any]? {
var result: [Any] = []
forEach {
result.append($0.filter{ $0.key == key }.map{ $0.value })
}
return result.isEmpty ? nil : result
}
}
var dicts: [[String: Any]] = [["key1": "value1", "key2": "value2"], ["key1": "value3", "key2": "value4"]]
dicts.values(of: "key1")
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