steventnorris steventnorris - 1 month ago 12
Swift Question

Make a dictionary value non-optional as extension

The below playground outlines my issue. The extension will remove nil values from my dictionary, but leave the other values as Optional(Value). What I need is a dictionary that has no nil values and make the optional value type non-optional.

Ex: I have a dictionary of

[String:Int?]
. I want the
jsonSantize()
of that called on that dictionary to return a
[String:Int]
.

//: Playground - noun: a place where people can play

import UIKit
import Foundation


protocol OptionalType {
associatedtype Wrapped
var asOptional : Wrapped? { get }
}

extension Optional : OptionalType {
var asOptional : Wrapped? {
return self
}
}

extension Dictionary where Value : OptionalType{

//Sanitizes the current dictionary for json serialization
//Removes nil values entirely. Makes optionals non-optional
func jsonSanitize() -> Dictionary<Key,Value> {
var newDict:[Key:Value] = [:]
for (key, value) in self {
if value.asOptional != nil {
newDict.updateValue(self[key]!, forKey: key)
}
}
return newDict
}

}

var youGood = false

var stringMan:String? = youGood ?
"WOHOO!" :
nil

var dict:[String:Any?] = [
"stuff":"THINGIES",
"things": stringMan

]
var dict2 = dict.jsonSanitize()
print(dict2)

var test = (stringMan != nil)


UPDATE: Suggestion made to use Value.Wrapped as new dictionary type

//: Playground - noun: a place where people can play

import UIKit
import Foundation


protocol OptionalType {
associatedtype Wrapped
var asOptional : Wrapped? { get }
}

extension Optional : OptionalType {
var asOptional : Wrapped? {
return self
}
}

extension Dictionary where Value : OptionalType{

//Sanitizes the current dictionary for json serialization
//Removes nil values entirely. Makes optionals non-optional
func jsonSanitize() -> Dictionary<Key,Value.Wrapped> {
var newDict:[Key:Value.Wrapped] = [:]
for (key, value) in self {
if let v = value.asOptional {
newDict.updateValue(v, forKey: key)
}
}
return newDict
}

}

var youGood = false

var stringMan:String? = youGood ?
"WOHOO!" :
nil

var dict:[String:Any?] = [
"stuff":"THINGIES",
"things": stringMan

]
var dict2:[String:Any] = dict.jsonSanitize()
print(dict2)

var test = (stringMan != nil)

Answer

Your method produces a dictionary of the same type [Key: Value] with Value being some optional type. What you probably want is to produce a dictionary of type [Key: Value.Wrapped]:

extension Dictionary where Value: OptionalType {

    func jsonSanitize() -> [Key: Value.Wrapped] {
        var newDict: [Key: Value.Wrapped] = [:]
        for (key, value) in self {
            if let v = value.asOptional {
                newDict.updateValue(v, forKey: key)
            }
        }
        return newDict
    }
}

Example:

let dict: [String: Int?] = [
    "foo": 1234,
    "bar": nil
]
var dict2 = dict.jsonSanitize()
print(dict2) // ["foo": 1234]

Note also that of Swift 3.0.1/Xcode 8.1 beta, optionals are bridged to NSNull instances automatically, see