Swift: How to remove a null value from Dictionary?

Swift 5

Use compactMapValues:

dictionary.compactMapValues { $0 }

compactMapValues has been introduced in Swift 5. For more info see Swift proposal SE-0218.

Example with dictionary

let json = [    "FirstName": "Anvar",    "LastName": "Azizov",    "Website": nil,    "About": nil,]let result = json.compactMapValues { $0 }print(result) // ["FirstName": "Anvar", "LastName": "Azizov"]

Example including JSON parsing

let jsonText = """  {    "FirstName": "Anvar",    "LastName": "Azizov",    "Website": null,    "About": null  }  """let data = jsonText.data(using: .utf8)!let json = try? JSONSerialization.jsonObject(with: data, options: [])if let json = json as? [String: Any?] {    let result = json.compactMapValues { $0 }    print(result) // ["FirstName": "Anvar", "LastName": "Azizov"]}

Swift 4

I would do it by combining filter with mapValues:

dictionary.filter { $0.value != nil }.mapValues { $0! }

Examples

Use the above examples just replace let result with

let result = json.filter { $0.value != nil }.mapValues { $0! }

You can create an array containing the keys whose corresponding values are nil:

let keysToRemove = dict.keys.array.filter { dict[$0]! == nil }

and next loop through all elements of that array and remove the keys from the dictionary:

for key in keysToRemove {    dict.removeValueForKey(key)}

Update 2017.01.17

The force unwrapping operator is a bit ugly, although safe, as explained in the comments. There are probably several other ways to achieve the same result, a better-looking way of the same method is:

let keysToRemove = dict.keys.filter {  guard let value = dict[$0] else { return false }  return value == nil}

I ended up with this in Swift 2:

extension Dictionary where Value: AnyObject {    var nullsRemoved: [Key: Value] {        let tup = filter { !($0.1 is NSNull) }        return tup.reduce([Key: Value]()) { (var r, e) in r[e.0] = e.1; return r }    }}

Same answer but for Swift 3:

extension Dictionary {    /// An immutable version of update. Returns a new dictionary containing self's values and the key/value passed in.    func updatedValue(_ value: Value, forKey key: Key) -> Dictionary<Key, Value> {        var result = self        result[key] = value        return result    }    var nullsRemoved: [Key: Value] {        let tup = filter { !($0.1 is NSNull) }        return tup.reduce([Key: Value]()) { $0.0.updatedValue($0.1.value, forKey: $0.1.key) }    }}

Things get a lot easier in Swift 4. Just use Dictionary's filter directly.

jsonResult.filter { !($0.1 is NSNull) }

Or if you don't want to remove the relevant keys, you can do this:

jsonResult.mapValues { $0 is NSNull ? nil : $0 }

Which will replace the NSNull values with nil instead of removing the keys.