Swift的字典排序问题

字典的例子

let dict = ["a": 1, "b": 2, "c": 3]

然后字典他是没有顺序的。运行的时候他的key，a,b,c会不定顺序

使用系统的方法：

let jsonData  = try? JSONSerialization.data(withJSONObject: dict, options: []) 

let jsonString = String(data: jsonData!, encoding: .utf8)

print(jsonString)
输出如下：
Optional("{\"b\":2,\"c\":3,\"a\":1}")

系统在iOS11的时候也有一个设置可以对字典排序

if #available(iOS 11.0, *) {
	let jsonData  = try? JSONSerialization.data(withJSONObject: dict, options: [.sortedKeys]) 

	let jsonString = String(data: jsonData!, encoding: .utf8)
  
	print(jsonString)
}
输出如下：
Optional("{\"a\":1,\"b\":2,\"c\":3}")

下面找了两种排序的方法。

方法一：

func creatJsonString(dict: [String:Any]) ->String{
    if(!JSONSerialization.isValidJSONObject(dict)) {
        print("无法解析出JSONString")
        return""
    }
    var namedPaird = [String]()
    let sortedKeysAndValues = dict.sorted{ $0.0 < $1.0 }
    for(key, value) in sortedKeysAndValues {
        if value is [String:Any] {
            namedPaird.append("\"\(key)\":\(creatJsonString(dict: value as! [String:Any]))")
        }else if value is [Any] {
            namedPaird.append("\"\(key)\":\(value)")
        }else{
            namedPaird.append("\"\(key)\":\"\(value)\"")
        }
    }
    let returnString = namedPaird.joined(separator:",")
    return"{\(returnString)}"
}

方法二：

class MutableOrderedDictionary: NSDictionary {
    let _values: NSMutableArray = []
    let _keys: NSMutableOrderedSet = []

    override var count: Int {
        return _keys.count
    }
    override func keyEnumerator() -> NSEnumerator {
        return _keys.objectEnumerator()
    }
    override func object(forKey aKey: Any) -> Any? {
        let index = _keys.index(of: aKey)
        if index != NSNotFound {
            return _values[index]
        }
        return nil
    }
    func setObject(_ anObject: Any, forKey aKey: String) {
        let index = _keys.index(of: aKey)
        if index != NSNotFound {
            _values[index] = anObject
        } else {
            _keys.add(aKey)
            _values.add(anObject)
        }
    }
}	
extension MutableOrderedDictionary {
    private static let defaultOrder: ((String, Any), (String, Any)) -> Bool = {
        $0.0.compare($1.0, options: [.forcedOrdering, .caseInsensitive]) == .orderedAscending
    }
    static func sorted(object: Any, by areInIncreasingOrder: ((key: String, value: Value), (key: String, value: Value)) -> Bool = defaultOrder) -> Any {
        if let dict = object as? [String: Any] {
            return MutableOrderedDictionary(dict, by: areInIncreasingOrder)
        } else if let array = object as? [Any] {
            return array.map { sorted(object: $0, by: areInIncreasingOrder) }
        } else {
            return object
        }
    }
    convenience init(_ dict: [String: Any], by areInIncreasingOrder: ((key: String, value: Value), (key: String, value: Value)) -> Bool = defaultOrder) {
        self.init()
        dict.sorted(by: areInIncreasingOrder)
            .forEach { setObject(MutableOrderedDictionary.sorted(object: $0.value, by: areInIncreasingOrder), forKey: $0.key) }
    }
}

用法：
// force ordering
let orderedJson = MutableOrderedDictionary(jsonObject)

// write pretty printed
_ = JSONSerialization.writeJSONObject(orderedJson, to: outputJSON, options: [.prettyPrinted], error: nil)

www.jianshu.com/p/326fc7815…

stackoverflow.com/questions/4…