I want my top level dictionary "Products" to store only a non empty dictionary of sub products. Is there a way to write the code below with higher order functions like reduce function instead using if !subProductDictionary.isEmpty ?
var productDictionary = [String: Any]()
productDictionary["key 1"] = "value 1"
var subProductDictionary = [String: Any]()
if !subProductDictionary.isEmpty {
productDictionary["subProductsKey"] = subProductDictionary
}
*** edit
I would like to use the fact that when Dictionaries do not store nil values, so to transform subProductDictionary to nil
I don't know about higher-order functions here but this might be useful:
extension Dictionary {
var nonEmpty: Self? {
isEmpty ? nil : self
}
}
var things: [String: Any] = [:]
let dict: [String: Any] = [:]
things["A"] = dict
things["B"] = dict.nonEmpty
Possible solution:
var productDictionary = [String: Any]()
productDictionary["key 1"] = "value 1"
var subProductDictionary = [String: Any]()
if !subProductDictionary.isEmpty {
productDictionary["subProductsKey"] = subProductDictionary
}
*** "Optional with flatMap" instead "if"
productDictionary["subProductsKey"] = Optional(subProductDictionary).flatMap { $0.count == 0 ? nil : $0 }
Please find below the code for proper and correct understanding:
var dictUpdateTasks = [String: String]()
var arrAddSteps = [String]()
self.dictUpdateTasks["dDay"] = self.btnAddDate.titleLabel?.text
self.dictUpdateTasks["rem"] = self.btnRemindMe.titleLabel?.text
self.dictUpdateTasks["steps"] = arrAddSteps
Now , this is the error, on line
"self.dictUpdateTasks["steps"] = arrAddSteps"
// Error: Cannot assign value of type '[String]' to type 'String?'
Please guide. Thanks.
Reason:
dictUpdateTasks is of type [String:String], i.e. it can accept values only of type String.
dictUpdateTasks["steps"] = arrAddSteps
But in the above code, you are trying to add [String] type value to dictUpdateTasks.
Solution:
Change the type of dictUpdateTasks from [String: String] to [String: Any],
var dictUpdateTasks = [String: Any]()
If you are looking for something like checking if the value exists or not by using isEmpty property of both the String and [String], on a higher level you could create a protocol separately for that. But for this scenario I would not recommend this.
protocol EmptyIdentifiable {
var isEmpty: Bool { get }
}
extension String: EmptyIdentifiable { }
extension Array: EmptyIdentifiable where Element == String { }
var dictionary = [String: EmptyIdentifiable]()
dictionary["string"] = "value"
dictionary["array"] = ["values1", "values2"]
print(dictionary["string"]?.isEmpty)
print(dictionary["array"]?.isEmpty)
Normal solution in this current situation would be to use casting from Any to String or [String].
if let array = dictionary["array"] as? [String] {
print(array, array.isEmpty)
}
if let string = dictionary["string"] as? String {
print(string, string.isEmpty)
}
Here is the correct way to create a dictionary.
Correct syntax
var dictUpdateTasks = [String: Any]()
You have created a dictionary with [String: String]() and you are assigned String Array arrAddSteps instead of String.
Please try this :
Need to make your dictionary type [String : Any]() instead of [String : String]()
In your case it will accept only String type in value
var dictUpdateTasks = [String: Any]()
var arrAddSteps = [String]()
self.dictUpdateTasks["dDay"] = self.btnAddDate.titleLabel?.text
self.dictUpdateTasks["rem"] = self.btnRemindMe.titleLabel?.text
self.dictUpdateTasks["steps"] = arrAddSteps
print(self.dictUpdateTasks)
You have to use key value pair to assign string to dictionary.
I have a multidimensional dictionary and I am trying to add data into it without deleting data, but overwrite if duplicate.
var items = [Int: AnyObject]()
var IdsAndDetails = [String:AnyObject]()
let index = 3 // static for test
...
for result in results {
// result is String (result also indicates itemId)
let details = self.IdsAndDetails[result]
// details is AnyObject like [String:String]
if let itemDetails = details {
// Here I want to append data into 'items' variable
// This doesn't work: (Error-1)
self.items[index]![result] = itemDetails
}
(Error-1):
Cannot assign to immutable expression to type AnyObject.
However, if I try like, it works but it's not the approach I want. It's re-creating the dictionary. Instead, I want to append the data.
self.items = [
index : [result : itemDetails]
]
The structure of dictionary I want to get in the end is:
items = [
index : [
"id1" : ["key": "value", "key": "value"],
"id2" : ["key": "val", "key": "val"],
],
index : [
"id3" : ["key": "val", "key": "val"],
"id4" : ["key": "val", "key": "val"],
"id5" : ["key": "val", "key": "val"],
]
]
// index is Integer
// [Key:Value] is [String:String] - itemDetails equal to all `[key:value]`s
// 'id' is also String
Update: I also tried, but no luck
let a = self.items[index]
a![result]! = itemDetails as [String:String]
Update 2:
let valueDict = (value as! NSDictionary) as Dictionary
for (key, val) in valueDict {
let keyString = key as! String
let valString = val as! String
self.items[index]![result]![keyString]! = valString
}
But it's throwing error:
fatal error: unexpectedly found nil while unwrapping an Optional value
But Surprisingly debugging shows all values:
po index : 1
po itemId : "123123"
po keyString: "keyInString"
po valString: "valInString"
Update 3:
for index in 1...5 {
var results = [String]()
// First I retrieve nearby users and assign it to key
let itemsRef = Firebase(url: self.secret + "/items")
eventsRef.queryOrderedByChild("user_id").queryEqualToValue(key).observeEventType(.ChildAdded, withBlock: { snapshot in
// ^ above 'key' is the user_id retrieved before
let itemDetails = snapshot.value // item details - [key:val, key:val]
let itemId = snapshot.key // item ids [id1,id2,id3]
// I used 'KeyAndDetails' to store all values with ids
let IdsAndDetails = [itemId: itemDetails]
self.itemIdsArray = []
self.itemIdsArray.append(itemId)
if index == 1 {
// self.items = [
// index : [itemId : itemDetails]
// ]
// ^ This worked and gave me the structure
// but I don't want to overwrite it, instead, I want to append
// on the dictionary
// This is where I am trying to append into `self.items`,
// and throws error:
self.items[index]?[result] = (eventDetails as! [String : String])
}
...
It seems like you're trying to bypass Swift's type system instead of working with it. Instead of using AnyObject, you should be trying to use the exact type you want for the value of that dictionary. In this case it looks like you want something like [Int: [String: [String: String]]] (although, like #EricD said in the comments, you should probably be using a struct instead, if at all possible).
Here's a quick (static) example similar to the code in your question:
var items = [Int: [String: [String: String]]]()
let idsAndDetails = ["id2": ["key3": "value3"]]
let index = 3
items[index] = ["id1": ["key1": "value1", "key2": "value2"]]
let result = "id2"
if let itemDetails = idsAndDetails[result] {
items[index]?[result] = itemDetails
}
At the end of that, items will be:
[3: ["id1": ["key1": "value1", "key2": "value2"], "id2": ["key3": "value3"]]]
The ? in items[index]?[result] tells Swift to make sure items[index] is non-nil before attempting to execute the subscript method. That way, if you try to update an index that doesn't exist in items you don't cause a crash.
I have this Swift code in which I'm trying to append a Dictionary to Array.
var savedFiles: [Dictionary<String, AnyObject>] = []
var newEntry = Dictionary<String,AnyObject>()
if let audio = receivedAudio?.filePathURL {
newEntry["url"] = audio
}
newEntry["name"] = caption
savedFiles.append(newEntry! as Dictionary<String,AnyObject>)
This gives me an error on last line (in append) Cannot invoke 'append' with an argument list of type '(Dictionary<String, AnyObject>)'
Any idea? I also tried remove force unwrapping as well.
Please try this:
var savedFiles: [[String: AnyObject]] = []
var newEntry: [String: AnyObject] = [:]
if let audio = receivedAudio?.filePathURL {
newEntry["url"] = audio
}
newEntry["name"] = caption
savedFiles.append(newEntry)
Hi just tried on playground its working, only you should know this: audio could be nil any time, in that case this key value pair won't be added in newEntryDictionary.
var savedFilesDictionary = [[String: AnyObject]]()
var newEntryDictionary = [String: AnyObject]()
var receivedAudio = NSURL(string: "/something/some")
if let audio = receivedAudio?.filePathURL {
newEntryDictionary["url"] = audio
}
newEntryDictionary["name"] = "some caption"
savedFilesDictionary.append(newEntryDictionary)
As of Swift 4, the correct way to work with dictionaries:
Declare empty dictionary (associative array):
var namesOfIntegers = [Int: String]()
Append to dictionary:
namesOfIntegers[16] = "sixteen"
Check if dictionary contains key:
let key = 16
if namesOfIntegers.keys.contains(key) {
// Does contain array key (will print 16)
print(namesOfIntegers[key])
}
See more, straight from Apple: https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/CollectionTypes.html
Absolutely no problem:
var savedFiles: [Dictionary<String, AnyObject>] = []
var newEntry = Dictionary<String, AnyObject>()
newEntry["key"] = "value"
savedFiles.append(newEntry)
Although this is the "Swifty"-Style:
var savedFiles = [[String: AnyObject]]()
var newEntry = [String: AnyObject]()
newEntry["key"] = "value"
savedFiles.append(newEntry)
I am using Xcode 7.2.1.
var savedFilesDictionary = [String: AnyObject]()
var newEntryDictionary = [String: AnyObject]()
if let audio = receivedAudio?.filePathURL {
newEntryDictionary["url"] = audio
}
newEntryDictionary["name"] = caption
savedFilesDictionary.append(newEntryDictionary)
Try this.
I am beginning to learn swift by following the iBook-The Swift Programming Language on Swift provided by Apple. The book says to create an empty dictionary one should use [:] same as while declaring array as []:
I declared an empty array as follows :
let emptyArr = [] // or String[]()
But on declaring empty dictionary, I get syntax error:
let emptyDict = [:]
How do I declare an empty dictionary?
var emptyDictionary = [String: String]()
var populatedDictionary = ["key1": "value1", "key2": "value2"]
Note: if you're planning to change the contents of the dictionary over time then declare it as a variable (var). You can declare an empty dictionary as a constant (let) but it would be pointless if you have the intention of changing it because constant values can't be changed after initialization.
You can't use [:] unless type information is available.
You need to provide it explicitly in this case:
var dict = Dictionary<String, String>()
var means it's mutable, so you can add entries to it.
Conversely, if you make it a let then you cannot further modify it (let means constant).
You can use the [:] shorthand notation if the type information can be inferred, for instance
var dict = ["key": "value"]
// stuff
dict = [:] // ok, I'm done with it
In the last example the dictionary is known to have a type Dictionary<String, String> by the first line. Note that you didn't have to specify it explicitly, but it has been inferred.
The Swift documentation recommends the following way to initialize an empty Dictionary:
var emptyDict = [String: String]()
I was a little confused when I first came across this question because different answers showed different ways to initialize an empty Dictionary. It turns out that there are actually a lot of ways you can do it, though some are a little redundant or overly verbose given Swift's ability to infer the type.
var emptyDict = [String: String]()
var emptyDict = Dictionary<String, String>()
var emptyDict: [String: String] = [:]
var emptyDict: [String: String] = [String: String]()
var emptyDict: [String: String] = Dictionary<String, String>()
var emptyDict: Dictionary = [String: String]()
var emptyDict: Dictionary = Dictionary<String, String>()
var emptyDict: Dictionary<String, String> = [:]
var emptyDict: Dictionary<String, String> = [String: String]()
var emptyDict: Dictionary<String, String> = Dictionary<String, String>()
After you have an empty Dictionary you can add a key-value pair like this:
emptyDict["some key"] = "some value"
If you want to empty your dictionary again, you can do the following:
emptyDict = [:]
The types are still <String, String> because that is how it was initialized.
Use this will work.
var emptyDict = [String: String]()
You can simply declare it like this:
var emptyDict:NSMutableDictionary = [:]
You have to give the dictionary a type
// empty dict with Ints as keys and Strings as values
var namesOfIntegers = Dictionary<Int, String>()
If the compiler can infer the type, you can use the shorter syntax
namesOfIntegers[16] = "sixteen"
// namesOfIntegers now contains 1 key-value pair
namesOfIntegers = [:]
// namesOfIntegers is once again an empty dictionary of type Int, String
Declaring & Initializing Dictionaries in Swift
Dictionary of String
var stringDict: [String: String] = [String: String]()
OR
var stringDict: Dictionary<String, String> = Dictionary<String, String>()
Dictionary of Int
var stringDict: [String: Int] = [String: Int]()
OR
var stringDict: Dictionary<String, Int> = Dictionary<String, Int>()
Dictionary of AnyObject
var stringDict: [String: AnyObject] = [String: AnyObject]()
OR
var stringDict: Dictionary<String, AnyObject> = Dictionary<String, AnyObject>()
Dictionary of Array of String
var stringDict: [String: [String]] = [String: [String]]()
OR
var stringDict: Dictionary<String, Array<String>> = Dictionary<String, Array<String>>()
Array of Dictionaries of String
var stringDict: [[String: String]] = [[String: String]]()
OR
var stringDict: Array<Dictionary<String, String>> = Array<Dictionary<String, String>>()
Swift:
var myDictionary = Dictionary<String, AnyObject>()
I'm playing with this too. It seems strange that you can just declare an empty dictionary and then add a key/value pair to it like so :
var emptyDictionary = Dictionary<String, Float>()
var flexDictionary = [:]
emptyDictionary["brian"] = 4.5
flexDictionary["key"] = "value" // ERROR : cannot assign to the result of this expression
But you can create a Dictionary that accepts different value types by using the "Any" type like so :
var emptyDictionary = Dictionary<String, Any>()
emptyDictionary["brian"] = 4.5
emptyDictionary["mike"] = "hello"
You need to explicitly tell the data type or the type can be inferred when you declare anything in Swift.
Swift 3
The sample below declare a dictionary with key as a Int type and the value as a String type.
Method 1: Initializer
let dic = Dictionary<Int, String>()
Method 2: Shorthand Syntax
let dic = [Int:String]()
Method 3: Dictionary Literal
var dic = [1: "Sample"]
// dic has NOT to be a constant
dic.removeAll()
If you want to create a generic dictionary with any type
var dictionaryData = [AnyHashable:Any]()
Swift 4
let dicc = NSDictionary()
//MARK: - This is empty dictionary
let dic = ["":""]
//MARK:- This is variable dic means if you want to put variable
let dic2 = ["":"", "":"", "":""]
//MARK:- Variable example
let dic3 = ["name":"Shakeel Ahmed", "imageurl":"https://abc?abc.abc/etc", "address":"Rawalpindi Pakistan"]
//MARK: - This is 2nd Variable Example dictionary
let dic4 = ["name": variablename, "city": variablecity, "zip": variablezip]
//MARK:- Dictionary String with Any Object
var dic5a = [String: String]()
//MARK:- Put values in dic
var dic5a = ["key1": "value", "key2":"value2", "key3":"value3"]
var dic5b = [String:AnyObject]()
dic5b = ["name": fullname, "imageurl": imgurl, "language": imgurl] as [String : AnyObject]
or
//MARK:- Dictionary String with Any Object
let dic5 = ["name": fullname, "imageurl": imgurl, "language": imgurl] as [String : AnyObject]
//MARK:- More Easy Way
let dic6a = NSDictionary()
let dic6b = NSMutalbeDictionary()
To create an empty dictionary with the [:] aka the empty dictionary literal, you actually need to provide the context first as in the type of both the key and the value. The correct way to use the [:] to create an empty dictionary is:
var dict: [String: Int] = [:]
I'm usually using
var dictionary:[String:String] = [:]
dictionary.removeAll()
You can declare it as nil with the following:
var assoc : [String:String]
Then nice thing is you've already typeset (notice I used var and not let, think of these as mutable and immutable). Then you can fill it later:
assoc = ["key1" : "things", "key2" : "stuff"]
You can use the following code:
var d1 = Dictionary<Int, Int>()
var d2 = [Int: Int]()
var d3: Dictionary<Int, Int> = [Int : Int]()
var d4: [Int : Int] = [:]
var dictList = String:String for dictionary in swift
var arrSectionTitle = String for array in swift
var parking = [Dictionary < String, Double >()]
^ this adds a dictionary for a [string:double] input
It is very handy for finding your way
var dict:Dictionary = [:]