I have declared a dictionary in Swift as so: var dict = [String: [String: [String]]]().
What I am trying to do now is to write to the nested dictionary. I have used both codes below, however, none of them work as the initial key does not exist:
dict["Test"]?["One"] = ["Failed"]
dict["Test"]!["One"] = ["Failed"]
What I am trying to do is to create a key for ["One"], much like how you can create a key for a normal dictionary using dict[key].
You need to instantiate every inner dictionary.
var dict = [String : [String : [String]]]()
dict["Test"] = [String : [String]]()
dict["Test"]?["One"] = ["Worked"]
print(dict)
Make sure to avoid force unwrapping.
dict is empty. There is no value for the "Test" key.
One option is to provide a default:
dict["Test", default: [:]]["One"] = ["A", "B"]
You can take this one step further:
dict["Test2", default: [:]]["Two", default: []].append("Hello")
That last line will work for any combination of the keys "Test2" and "Two" existing or not before that is used.
I have a struct that looks like:
struct nameStruct {
let name: String
let index: Int
}
I have an NSMutableArray that contains about 50 objects of this struct
Right now, I fill the contents of my namesDict with
let namesDict:[String: Any] = ["names" : namesArray]
However, because I only need the index object for sorting, I'd like to only add the name attribute to the dictionary, something like this:
let namesDict:[String: Any] = ["names" : namesArray.name]
or, because of swift's nature:
let namesDict:[String: Any] = ["names" : (namesArray as! [nameStruct]).name]
(focus on the .name part which obviously doesn't work in Swift)
Right now, my best guess would be to create a new array in a loop, only adding the name of the contents of my namesArray - but if there was a way to do this in one line without another array "in between", this would be really nice.
You can use map.
let namesDict: [String: Any] = ["names": namesArray.map({ ($0 as! nameStruct).name })]
In my Swift3 code I have an array:
var eventParams =
[ "fields" :
[ "photo_url":uploadedPhotoURL,
"video_url":uploadedVideoURL
]
]
Later on I want to add another array to this array, I thought I could just do:
eventParams["fields"]["user_location"] = [
"type":"Point", "coordinates":[appDelegate.longitude, appDelegate.latitude]
]
but I'm getting error here:
Type Any? has no subscript members
How can I add that array to my previously declared array fields?
Since your dictionary is declared as [String : Any], the compiler doesn't know that the value for "fields" is actually a dictionary itself. It just knows that it's Any. One very simple way to do what you're trying is like this:
(eventParams["fields"] as? [String : Any])?["user_location"] = [
"type":"Point", "coordinates":[appDelegate.longitude, appDelegate.latitude]
]
This will just do nothing if eventParams["fields"] is nil, or if it's not actually [String : Any].
You can also do this in a couple steps to allow for troubleshooting later on like this:
//Get a reference to the "fields" dictionary, or create a new one if there's nothig there
var fields = eventParams["fields"] as? [String : Any] ?? [String : Any]()
//Add the "user_location" value to the fields dictionary
fields["user_location"] = ["type":"Point", "coordinates":[appDelegate.longitude, appDelegate.latitude]]
//Reassign the new fields dictionary with user location added
eventParams["fields"] = fields
I have a simple Dictionary which is defined like:
var dict : NSDictionary = [ 1 : "abc", 2 : "cde"]
Now I want to add an element into this dictionary: 3 : "efg"
How can I append 3 : "efg" into this existing dictionary?
You're using NSDictionary. Unless you explicitly need it to be that type for some reason, I recommend using a Swift dictionary.
You can pass a Swift dictionary to any function expecting NSDictionary without any extra work, because Dictionary<> and NSDictionary seamlessly bridge to each other. The advantage of the native Swift way is that the dictionary uses generic types, so if you define it with Int as the key and String as the value, you cannot mistakenly use keys and values of different types. (The compiler checks the types on your behalf.)
Based on what I see in your code, your dictionary uses Int as the key and String as the value. To create an instance and add an item at a later time you can use this code:
var dict = [1: "abc", 2: "cde"] // dict is of type Dictionary<Int, String>
dict[3] = "efg"
If you later need to assign it to a variable of NSDictionary type, just do an explicit cast:
let nsDict = dict as! NSDictionary
And, as mentioned earlier, if you want to pass it to a function expecting NSDictionary, pass it as-is without any cast or conversion.
you can add using the following way and change Dictionary to NSMutableDictionary
dict["key"] = "value"
I know this might be coming very late, but it may prove useful to someone.
So for appending key value pairs to dictionaries in swift, you can use updateValue(value: , forKey: ) method as follows :
var dict = [ 1 : "abc", 2 : "cde"]
dict.updateValue("efg", forKey: 3)
print(dict)
SWIFT 3 - XCODE 8.1
var dictionary = [Int:String]()
dictionary.updateValue(value: "Hola", forKey: 1)
dictionary.updateValue(value: "Hello", forKey: 2)
dictionary.updateValue(value: "Aloha", forKey: 3)
So, your dictionary contains:
dictionary[1: Hola, 2: Hello, 3: Aloha]
If your dictionary is Int to String you can do simply:
dict[3] = "efg"
If you mean adding elements to the value of the dictionary a possible solution:
var dict = Dictionary<String, Array<Int>>()
dict["key"]! += [1]
dict["key"]!.append(1)
dict["key"]?.append(1)
Swift 3+
Example to assign new values to Dictionary. You need to declare it as NSMutableDictionary:
var myDictionary: NSMutableDictionary = [:]
let newValue = 1
myDictionary["newKey"] = newValue
print(myDictionary)
For whoever reading this for swift 5.1+
// 1. Using updateValue to update the given key or add new if doesn't exist
var dictionary = [Int:String]()
dictionary.updateValue("egf", forKey: 3)
// 2. Using a dictionary[key]
var dictionary = [Int:String]()
dictionary[key] = "value"
// 3. Using subscript and mutating append for the value
var dictionary = [Int:[String]]()
dictionary[key, default: ["val"]].append("value")
In Swift, if you are using NSDictionary, you can use setValue:
dict.setValue("value", forKey: "key")
Given two dictionaries as below:
var dic1 = ["a": 1, "c": 2]
var dic2 = ["e": 3, "f": 4]
Here is how you can add all the items from dic2 to dic1:
dic2.forEach {
dic1[$0.key] = $0.value
}
Dict.updateValue updates value for existing key from dictionary or adds new new key-value pair if key does not exists.
Example-
var caseStatusParams: [String: AnyObject] = ["userId" : UserDefault.userID ]
caseStatusParams.updateValue("Hello" as AnyObject, forKey: "otherNotes")
Result-
▿ : 2 elements
- key : "userId"
- value : 866
▿ : 2 elements
- key : "otherNotes"
- value : "Hello"
[String:Any]
For the fellows using [String:Any] instead of Dictionary below is the extension
extension Dictionary where Key == String, Value == Any {
mutating func append(anotherDict:[String:Any]) {
for (key, value) in anotherDict {
self.updateValue(value, forKey: key)
}
}
}
As of Swift 5, the following code collection works.
// main dict to start with
var myDict : Dictionary = [ 1 : "abc", 2 : "cde"]
// dict(s) to be added to main dict
let myDictToMergeWith : Dictionary = [ 5 : "l m n"]
let myDictUpdated : Dictionary = [ 5 : "lmn"]
let myDictToBeMapped : Dictionary = [ 6 : "opq"]
myDict[3]="fgh"
myDict.updateValue("ijk", forKey: 4)
myDict.merge(myDictToMergeWith){(current, _) in current}
print(myDict)
myDict.merge(myDictUpdated){(_, new) in new}
print(myDict)
myDictToBeMapped.map {
myDict[$0.0] = $0.1
}
print(myDict)
To add new elements just set:
listParameters["your parameter"] = value
There is no function to append the data in dictionary. You just assign the value against new key in existing dictionary. it will automatically add value to the dictionary.
var param = ["Name":"Aloha","user" : "Aloha 2"]
param["questions"] = "Are you mine?"
print(param)
The output will be like
["Name":"Aloha","user" : "Aloha 2","questions" : ""Are you mine"?"]
To append a new key-value pair to a dictionary you simply have to set the value for the key. for eg.
// Initialize the Dictionary
var dict = ["name": "John", "surname": "Doe"]
// Add a new key with a value
dict["email"] = "john.doe#email.com"
print(dict)
Output -> ["surname": "Doe", "name": "John", "email": "john.doe#email.com"]
var dict = ["name": "Samira", "surname": "Sami"]
// Add a new enter code herekey with a value
dict["email"] = "sample#email.com"
print(dict)
Up till now the best way I have found to append data to a dictionary by using one of the higher order functions of Swift i.e. "reduce". Follow below code snippet:
newDictionary = oldDictionary.reduce(*newDictionary*) { r, e in var r = r; r[e.0] = e.1; return r }
#Dharmesh In your case, it will be,
newDictionary = dict.reduce([3 : "efg"]) { r, e in var r = r; r[e.0] = e.1; return r }
Please let me know if you find any issues in using above syntax.
Swift 5 happy coding
var tempDicData = NSMutableDictionary()
for temp in answerList {
tempDicData.setValue("your value", forKey: "your key")
}
I added Dictionary extension
extension Dictionary {
func cloneWith(_ dict: [Key: Value]) -> [Key: Value] {
var result = self
dict.forEach { key, value in result[key] = value }
return result
}
}
you can use cloneWith like this
newDictionary = dict.reduce([3 : "efg"]) { r, e in r.cloneWith(e) }
if you want to modify or update NSDictionary then
first of all typecast it as NSMutableDictionary
let newdictionary = NSDictionary as NSMutableDictionary
then simply use
newdictionary.setValue(value: AnyObject?, forKey: String)
I'm looking for a straightforward way of converting a dictionary of type [String : Any?] to a dictionary of [String: AnyObject]. I could loop through the elements individually, but that just seems 'wrong' to me.
If I just try to cast the original dictionary, I get a crash.
let dict:[String : Any?] = ["something" : "else"]
// crashes with fatal error: 'can't unsafeBitCast
// between types of different sizes'
let newDict = dict as? [String: AnyObject]
Looping is exactly correct, and Swift encourages this. The most efficient and Swift-like (*) approach is:
var result = [String: AnyObject]()
for (key, value) in dict {
if let v = value as? AnyObject {
result[key] = v
}
}
(*) This isn't really "Swift-like" because it includes AnyObject, which should almost never be part of a non-temporary data structure. A proper Swift implementation would convert AnyObject to a real type.
Note that the crash you get is definitely not appropriate and you should open a radar (bugreport.apple.com). An as? should never crash like this. You should either get nil or a compiler failure.
Warning: as #rob-napier mentioned in the comments, its O(n^2) so this approach is only valid for small dictionaries (less than 100 elements).
You can use reduce:
let dict:[String : Any?] = ["something" : "else"]
let newDict = dict.reduce([String: AnyObject](), combine: { accumulator, pair in
var temp = accumulator
temp[pair.0] = pair.1 as? AnyObject
return temp
})
Here newDict is of type [String: AnyObject].