支持嵌套`NSNull`

Question

我有下面的字典代码

var dic : [String: AnyObject] = ["FirstName": "Anvar", "LastName": "Azizov", "Website": NSNull(),"About": NSNull()]

我已经使用下面的代码

删除了具有空值的键

var keys = dic.keys.array.filter({dic[$0] is NSNull})
for key in keys {
  dic.removeValueForKey(key)
}

它适用于静态字典，但我想动态地做，我想用函数完成它但是每当我将字典作为参数传递时它就像一个let意味着常量，所以不能删除null键我在下面编写代码

func nullKeyRemoval(dic : [String: AnyObject]) -> [String: AnyObject]{
        var keysToRemove = dic.keys.array.filter({dic[$0] is NSNull})
        for key in keysToRemove {
            dic.removeValueForKey(key)
        }
        return dic
}

请告诉我这个解决方案

Answer 1

不是使用全局函数（或方法），为什么不使用扩展名将其作为Dictionary的方法？

extension Dictionary {
    func nullKeyRemoval() -> Dictionary {
        var dict = self

        let keysToRemove = Array(dict.keys).filter { dict[$0] is NSNull }
        for key in keysToRemove {
            dict.removeValue(forKey: key)
        }

        return dict
    }
}

它适用于任何泛型类型（不限于String, AnyObject），您可以直接从字典本身调用它：

var dic : [String: AnyObject] = ["FirstName": "Anvar", "LastName": "Azizov", "Website": NSNull(),"About": NSNull()]
let dicWithoutNulls = dic.nullKeyRemoval()

Answer 2

对于add_action( 'template_redirect', 'redirect_to_homepage' ); function redirect_to_homepage() { $homepage_id = get_option('page_on_front') if ( ! is_page( $homepage_id ) ) { wp_redirect( home_url( 'index.php?page_id=' . $homepage_id ) ); } }，这可能会有所帮助。同时删除递归的render() { return ( <div ref="root" className={s.root}> // ---- </div> )}; onChange(state) { if(this.refs.root) { this.setState(state); } }个对象：

Swift 3.0 / 3.1

Answer 3

Swift 3：从词典中删除null

 func removeNSNull(from dict: [String: Any]) -> [String: Any] {
    var mutableDict = dict
    let keysWithEmptString = dict.filter { $0.1 is NSNull }.map { $0.0 }
    for key in keysWithEmptString {
        mutableDict[key] = ""
    }
    return mutableDict
}

使用：

let outputDict = removeNSNull(from: ["name": "Foo", "address": NSNull(), "id": "12"])

输出：[“name”：“Foo”，“address”：“”，“id”：“12”]

Answer 4

不是使用全局函数（或方法），为什么不使用扩展名将其作为Dictionary的方法呢？

   extension NSDictionary
    {
        func RemoveNullValueFromDic()-> NSDictionary
        {
            let mutableDictionary:NSMutableDictionary = NSMutableDictionary(dictionary: self)
            for key in mutableDictionary.allKeys
            {
                if("\(mutableDictionary.objectForKey("\(key)")!)" == "<null>")
                {
                    mutableDictionary.setValue("", forKey: key as! String)
                }
                else if(mutableDictionary.objectForKey("\(key)")!.isKindOfClass(NSNull))
                {
                    mutableDictionary.setValue("", forKey: key as! String)
                }
                else if(mutableDictionary.objectForKey("\(key)")!.isKindOfClass(NSDictionary))
                {
                    mutableDictionary.setValue(mutableDictionary.objectForKey("\(key)")!.RemoveNullValueFromDic(), forKey: key as! String)
                }
            }
            return mutableDictionary
        }
    }

Answer 5

Swift 4

比其他解决方案更有效率。仅使用O(n)复杂度。

extension Dictionary where Key == String, Value == Any? {

    var trimmingNullValues: [String: Any] {
        var copy = self
        forEach { (key, value) in
            if value == nil {
                copy.removeValue(forKey: key)
            }
        }
        return copy as [Key: ImplicitlyUnwrappedOptional<Value>]
    }
}

Usage: ["ok": nil, "now": "k", "foo": nil].trimmingNullValues // = ["now": "k"]

如果您的字典是可变的，您可以在适当的位置执行此操作并防止低效复制：

extension Dictionary where Key == String, Value == Any? {
    mutating func trimNullValues() {
        forEach { (key, value) in
            if value == nil {
                removeValue(forKey: key)
            }
        }            
    }
}

Usage: var dict: [String: Any?] = ["ok": nil, "now": "k", "foo": nil] dict.trimNullValues() // dict now: = ["now": "k"]

Answer 6

使用reduce

的Swift 4示例

let dictionary = [
  "Value": "Value",
  "Nil": nil
]

dictionary.reduce([String: String]()) { (dict, item) in

  guard let value = item.value else {
    return dict
  }

  var dict = dict
  dict[item.key] = value
  return dict
}

Answer 7

最干净的方法，只有1行

extension Dictionary {
    func filterNil() -> Dictionary {
        return self.filter { !($0.value is NSNull) }
    }
}

Answer 8

Swift 5添加compactMapValues(_:)，让您可以这么做

let filteredDict = dict.compactMapValues { $0 is NSNull ? nil : $0 }

Answer 9

支持嵌套`NSNull`

要删除任何嵌套级别（包括数组和字典）中的任何 NSNull外观，请尝试以下操作：

extension Dictionary where Key == String {
    func removeNullsFromDictionary() -> Self {
        var destination = Self()
        for key in self.keys {
            guard !(self[key] is NSNull) else { destination[key] = nil; continue }
            guard !(self[key] is Self) else { destination[key] = (self[key] as! Self).removeNullsFromDictionary() as? Value; continue }
            guard self[key] is [Value] else { destination[key] = self[key]; continue }

            let orgArray = self[key] as! [Value]
            var destArray: [Value] = []
            for item in orgArray {
                guard let this = item as? Self else { destArray.append(item); continue }
                destArray.append(this.removeNullsFromDictionary() as! Value)
            }
            destination[key] = destArray as? Value
        }
        return destination
    }
}

使用函数从swift字典中动态删除空值

9 个答案:

支持嵌套`NSNull`

使用函数从swift字典中动态删除空值

9 个答案:

支持嵌套NSNull

支持嵌套`NSNull`