I am having an array of dictionaries with columnId and columnValue as a pair. Now i need to flatten it as columnId as the key and columnValue as the value of it. How is it possible to do with swift higher order functions?
let arrayOfDictionaries = [["columnId": 123, "columnValue": "sample text"], ["columnId": 124, "columnValue": 9977332]]
//The end result should be:
flattenedDictionary: [String: Any] = ["123": "sample text", "124": 9977332]
Note: Result dictionary will be in the form of [String: Any]
This would work:
func flatten(_ pairs: [[String: Any]]) -> [String: Any] {
pairs.reduce(into: [String: Any]()) {
if let id = $1["columnId"] as? Int, let value = $1["columnValue"] {
$0["\(id)"] = value
}
}
}
You can do this in two steps;
Convert your input array into a sequence of key-value pairs using compactMap
Convert the sequence back into a dictionary using Dictionary(uniqueKeysWithValues:)
let arrayOfDictionaries = [["columnId": 123, "columnValue": "sample text"], ["columnId": 124, "columnValue": 9977332]]
let tupleArray:[(String,Any)] = arrayOfDictionaries.compactMap { dict in
guard let id = dict["columnId"], let value = dict["columnValue"] else {
return nil
}
return ("\(id)",value)
}
let flattenedDictionary: [String: Any] = Dictionary(uniqueKeysWithValues: tupleArray)
Note that this code will throw an exception if there are duplicate keys. You should either take steps to ensure the columnId values are unique or use Dictionary(keysAndValues:, uniquingKeysWith:) to resolve id clashes.
Related
I have a data structure in a Dictionary which looks like this:
- device
- type
- isActive
- Data
- Manufacturer
- Build Date
- Power
...
- Example
Now if I create a For Loop it only shows me the Values of the First level which means
type, isActive, Data, Example
for (key, value) in value {
}
All below Data like Build Date or Power is Missing - how can I irritate through this levels also?
Assuming you have Dictionary with type [String:Any], function to flatten it will be something like:
func flatten(_ obj:[String:Any]) -> [String:Any] {
var result = [String:Any]()
for (key, val) in obj {
if let v = val as? [String:Any] {
result = result.merging(flatten(v), uniquingKeysWith: {
$1
})
}
//I also included initial value of internal dictionary
/if you don't need initial value put next line in 'else'
result[key] = val
}
return result
}
To use that:
let d:[String:Any] = [
"test1":1,
"test2":2,
"test3":[
"test3.1":31,
"test3.2":32
]
]
let res = flatten(d)
print(res)
["test2": 2, "test3.2": 32, "test3.1": 31, "test1": 1, "test3":
["test3.2": 32, "test3.1": 31]]
note: dictionaries are not sorted structures
You are dealing with a Recursion problem here.
You could walk the dictionary level by level:
func walk(dictionary: [String: Any]) {
for (key, value) in dictionary {
print("\(key): \(value)")
if let value = value as? [String: Any] {
walk(dictionary: value)
}
}
}
You can change [String: Any] type with your dictionary type (NSDictionary, etc.)
As Tomas says, this can be solved with recursion. His "walk" function simply prints the values on separate lines, but with no keys, and not formatting. Here is code that logs nested dictionaries using the structure you outlined:
//Define the keys we use in our example
enum keys: String {
case device
case type
case isActive
case Data
case Manufacturer
case BuildDate
case Power
case Example
}
//Create a sample dictionary using those keys and some random values
let dict = [keys.device.rawValue:
[keys.type.rawValue: "appliance",
keys.isActive.rawValue: true,
keys.Data.rawValue:
[keys.Manufacturer.rawValue: "GE",
keys.BuildDate.rawValue: "12/23/96",
keys.Power.rawValue: 23,
],
keys.Example.rawValue: "Foo"
]
]
//Create an extension of Dictionary for dictionaries with String Keys.
extension Dictionary where Key == String {
//Define a function to recursively build a description of our dictionary
private func descriptionOfDict(_ aDict: [String: Any], level: Int = 0) -> String {
var output = ""
var indent: String = ""
if level > 0 {
output += "\n"
for _ in 1...level {
indent += " "
}
}
for (key,value) in aDict {
output += indent + key + ": "
if let subDict = value as? [String: Any] {
//If the value for this key is another dictionary, log that recursively
output += descriptionOfDict(subDict, level: level+1)
} else {
if let aString = value as? String {
output += "\"" + aString + "\"\n"
} else {
output += String(describing: value) + "\n"
}
}
}
return output
}
//Add a description property for dictionaries
var description: String {
return descriptionOfDict(self)
}
}
print(dict.description)
That outputs:
device:
isActive: true
Data:
Manufacturer: "GE"
Power: 23
BuildDate: "12/23/96"
Example: "Foo"
type: "appliance"
Edit:
The above, defining a String property description, changes the output when you print a [String:Any] dictionary. If you don't want that, rename the property description to something else like dictDescription
var clariQuestion: [String: String] = ["0": "What are my last 10 transactions",
"1": "What are my spending transactions",
"2": "What are my largest trasactions",
"3": "What are my pending tracnstions"]
var explanationActionParameters: [String: Any] = ["clariQuestion": 2]
So i need to match the value of explanationActionParameters with the key of clariQuestion, and then when the keys match replace the number 2 in explanationActionParameters with "what are my largest transactions". What's causing me difficulty is that the value in explanationActionParameter is of type 2 and the key in clariQuestion is of type String. Not to sure how to go about this.
You can either convert your int to string, using String(2) or convert your string to int, like Int("2")
My answer to you would be to transform your clariQuestion dictionary into an array, because the keys are integers, and an array can be seen as a dictionary where the keys are integers. So, you could do
var clariQuestion: [String] = ["What are my last 10 transactions",
"What are my spending transactions",
"What are my largest trasactions",
"What are my pending tracnstions"]
var explanationActionParameters: [String: Any] = ["clariQuestion": 2]
let questionIndex = explanationActionParameters["clariQuestion"]
let question = clariQuestion[questionIndex]
If you insist on maintaining this dictionary structure, you can flatmap your dictionaries and transform all keys from string to int, like this
clariQuestion.flatMap { (key, value) in [Int(key) : value] }
or transform all your values to a string, like this
explanationActionParameters.flatMap { (key, value) in [key : String(value)] }
Either way, now you should be able to access elements across those dictionaries. I'm going to create a function demonstrating how
func replace(_ clariQuestion: [String : String], _ explanationActionParameters: [String: Any]) -> [String: String] {
// The dictionary that will be returned containing the mapping from clariQuestion to explanationActionParameters
var ret = [String : String]()
let mappedClariQuestion = clariQuestion.flatMap { (key, value) in [Int(key) : value] }
for (key, value) in clariQuestion {
ret[key] = mappedClariQuestion[value]
}
return ret
}
Then, just explanationActionParameters = replace(clariQuestion, explanationActionParameters)
I'm trying to extract the info from a json array and i'm getting this error
"Cannot subscript a value of type '[[String : Any]]' with an index of type 'String'"
here
if let rev = place.details?["reviews"] as? [[String:Any]] {
if let ver = rev["author_name"] as? String { // <- IN THIS LINE I GET THE ERROR
}
}
i know that if i cast the type as [String : Any] instead of [[String:Any]] it will work, but in this case i have to cast it as an array of arrays otherwise it doesn't read the json, so how can i solve the problem?
[[String:Any]] is an array. It can be only subscripted by Int index.
You have to iterate over the array for example:
if let reviews = place.details?["reviews"] as? [[String:Any]] {
for review in reviews {
if let authorName = review["author_name"] as? String {
// do something with authorName
}
}
}
You can't access an item in an array with a String. You have to use Int
[[String:Any]] This is an array of dictionaries.
[[String:Any]] is a two dimensional Array. It can be only subscripted using Int index.
It is better to use a forEach loop, e.g.
if let reviews = place.details?["reviews"] as? [[String:Any]] {
reviews?.forEach { review in
if let authorName = review["author_name"] as? String {
// do something with authorName
}
}
}
I think you are mixing up dictionaries and arrays here.
If you want to access an element in an array, you have to use an Int index like this
let a = ["test", "some", "more"] // your array
let b = a[0] // print(b) = "test"
If you want to access an element in a dictionary, you can access it via its key, in your case a String
let dict: [String: Any] = ["aKey": "someValue"]
let value = dict["aKey"] // print(value) = "someValue"
In your case you have an array of dictionaries, each of them containing information about a review. If you want to access the author of one of your reviews, you have to first get the review dictionary out of your array like this:
if let reviews = place.details?["reviews"] as? [[String:Any]],
let review = reviews[0] {
// here you can access the author of the review then:
if let author = review["author_name"] as? String {
// do something
}
}
Instead of accessing just the first review like in my example, you can also loop via the array to access all of the reviews one by one
I have a Dictionary that contains values in such a way that some values are empty string.
let fbPostDic: [String: AnyObject] = [
"title":"",
"first_name”:”Ali“,
"last_name”:”Ahmad“,
"nick_name”:”ahmad”,
"gender":1,
"gender_visibility":2,
"dob":"1985-08-25",
"dob_visibility":2,
"city":"Lahore",
"city_visibility":2,
"bio”:”Its bio detail.”,
"bio_visibility":2,
"nationality":"Pakistan",
"nationality_visibility":2,
"relationship_status”:”Single”,
"rel_status_visibility":2,
"relation_with":"",
"relation_with_visibility":2,
"social_media_source":"Facebook",
]
I want to filter this dictionary such a way that new dictionary should just contains elements without empty strings.
let fbPostDic: [String: AnyObject] = [
"first_name”:”Ali“,
"last_name”:”Ahmad“,
"nick_name”:”ahmad”,
"gender":1,
"gender_visibility":2,
"dob":"1985-08-25",
"dob_visibility":2,
"city":"Lahore",
"city_visibility":2,
"bio”:”Its bio detail.”,
"bio_visibility":2,
"nationality":"Pakistan",
"nationality_visibility":2,
"relationship_status”:”Single”,
"rel_status_visibility":2,
"relation_with_visibility":2,
"social_media_source":"Facebook",
]
There are present ways like
let keysToRemove = dict.keys.array.filter { dict[$0]! == nil }
But its support iOS9.0 or above. I want to give support of iOS8.0 as well.
Any suggestions?
Because the above dict is a constant, add an extra init method in Dictionary extension can simplify the process:
extension Dictionary where Key: StringLiteralConvertible, Value: AnyObject {
init(_ elements: [Element]){
self.init()
for (key, value) in elements {
self[key] = value
}
}
}
print(Dictionary(dict.filter { $1 as? String != "" }))
However, if above dict can be declared as a variable. Probably try the one below without above extra Dictionary extension:
var dict: [String : AnyObject] = [...]
dict.forEach { if $1 as? String == "" { dict.removeValueForKey($0) } }
print(dict)
This solution will also work; But Allen's solution is more precise.
public class func filterDictionaryFromEmptyString(var dictionary:[String: AnyObject]) -> [String: AnyObject]
{
print(dictionary.keys.count)
for key:String in dictionary.keys
{
print(key)
print(dictionary[key]!)
if String(dictionary[key]!) == ""
{
dictionary.removeValueForKey(key)
}
}
print(dictionary.keys.count)
return dictionary
}
Trying to fill an array with strings from the keys in a dictionary in swift.
var componentArray: [String]
let dict = NSDictionary(contentsOfFile: NSBundle.mainBundle().pathForResource("Components", ofType: "plist")!)
componentArray = dict.allKeys
This returns an error of: 'AnyObject' not identical to string
Also tried
componentArray = dict.allKeys as String
but get: 'String' is not convertible to [String]
Swift 3 & Swift 4
componentArray = Array(dict.keys) // for Dictionary
componentArray = dict.allKeys // for NSDictionary
With Swift 3, Dictionary has a keys property. keys has the following declaration:
var keys: LazyMapCollection<Dictionary<Key, Value>, Key> { get }
A collection containing just the keys of the dictionary.
Note that LazyMapCollection that can easily be mapped to an Array with Array's init(_:) initializer.
From NSDictionary to [String]
The following iOS AppDelegate class snippet shows how to get an array of strings ([String]) using keys property from a NSDictionary:
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
let string = Bundle.main.path(forResource: "Components", ofType: "plist")!
if let dict = NSDictionary(contentsOfFile: string) as? [String : Int] {
let lazyMapCollection = dict.keys
let componentArray = Array(lazyMapCollection)
print(componentArray)
// prints: ["Car", "Boat"]
}
return true
}
From [String: Int] to [String]
In a more general way, the following Playground code shows how to get an array of strings ([String]) using keys property from a dictionary with string keys and integer values ([String: Int]):
let dictionary = ["Gabrielle": 49, "Bree": 32, "Susan": 12, "Lynette": 7]
let lazyMapCollection = dictionary.keys
let stringArray = Array(lazyMapCollection)
print(stringArray)
// prints: ["Bree", "Susan", "Lynette", "Gabrielle"]
From [Int: String] to [String]
The following Playground code shows how to get an array of strings ([String]) using keys property from a dictionary with integer keys and string values ([Int: String]):
let dictionary = [49: "Gabrielle", 32: "Bree", 12: "Susan", 7: "Lynette"]
let lazyMapCollection = dictionary.keys
let stringArray = Array(lazyMapCollection.map { String($0) })
// let stringArray = Array(lazyMapCollection).map { String($0) } // also works
print(stringArray)
// prints: ["32", "12", "7", "49"]
Array from dictionary keys in Swift
componentArray = [String] (dict.keys)
You can use dictionary.map like this:
let myKeys: [String] = myDictionary.map{String($0.key) }
The explanation:
Map iterates through the myDictionary and accepts each key and value pair as $0. From here you can get $0.key or $0.value. Inside the trailing closure {}, you can transform each element and return that element. Since you want $0 and you want it as a string then you convert using String($0.key). You collect the transformed elements to an array of strings.
dict.allKeys is not a String. It is a [String], exactly as the error message tells you (assuming, of course, that the keys are all strings; this is exactly what you are asserting when you say that).
So, either start by typing componentArray as [AnyObject], because that is how it is typed in the Cocoa API, or else, if you cast dict.allKeys, cast it to [String], because that is how you have typed componentArray.
extension Array {
public func toDictionary<Key: Hashable>(with selectKey: (Element) -> Key) -> [Key:Element] {
var dict = [Key:Element]()
for element in self {
dict[selectKey(element)] = element
}
return dict
}
}
dict.keys.sorted()
that gives [String]
https://developer.apple.com/documentation/swift/array/2945003-sorted
From the official Array Apple documentation:
init(_:) - Creates an array containing the elements of a sequence.
Declaration
Array.init<S>(_ s: S) where Element == S.Element, S : Sequence
Parameters
s - The sequence of elements to turn into an array.
Discussion
You can use this initializer to create an array from any other type that conforms to the Sequence protocol...You can also use this initializer to convert a complex sequence or collection type back to an array. For example, the keys property of a dictionary isn’t an array with its own storage, it’s a collection that maps its elements from the dictionary only when they’re accessed, saving the time and space needed to allocate an array. If you need to pass those keys to a method that takes an array, however, use this initializer to convert that list from its type of LazyMapCollection<Dictionary<String, Int>, Int> to a simple [String].
func cacheImagesWithNames(names: [String]) {
// custom image loading and caching
}
let namedHues: [String: Int] = ["Vermillion": 18, "Magenta": 302,
"Gold": 50, "Cerise": 320]
let colorNames = Array(namedHues.keys)
cacheImagesWithNames(colorNames)
print(colorNames)
// Prints "["Gold", "Cerise", "Magenta", "Vermillion"]"
Swift 5
var dict = ["key1":"Value1", "key2":"Value2"]
let k = dict.keys
var a: [String]()
a.append(contentsOf: k)
This works for me.
NSDictionary is Class(pass by reference)
Dictionary is Structure(pass by value)
====== Array from NSDictionary ======
NSDictionary has allKeys and allValues get properties with
type [Any].
let objesctNSDictionary =
NSDictionary.init(dictionary: ["BR": "Brazil", "GH": "Ghana", "JP": "Japan"])
let objectArrayOfAllKeys:Array = objesctNSDictionary.allKeys
let objectArrayOfAllValues:Array = objesctNSDictionary.allValues
print(objectArrayOfAllKeys)
print(objectArrayOfAllValues)
====== Array From Dictionary ======
Apple reference for Dictionary's keys and values properties.
let objectDictionary:Dictionary =
["BR": "Brazil", "GH": "Ghana", "JP": "Japan"]
let objectArrayOfAllKeys:Array = Array(objectDictionary.keys)
let objectArrayOfAllValues:Array = Array(objectDictionary.values)
print(objectArrayOfAllKeys)
print(objectArrayOfAllValues)
This answer will be for swift dictionary w/ String keys. Like this one below.
let dict: [String: Int] = ["hey": 1, "yo": 2, "sup": 3, "hello": 4, "whassup": 5]
Here's the extension I'll use.
extension Dictionary {
func allKeys() -> [String] {
guard self.keys.first is String else {
debugPrint("This function will not return other hashable types. (Only strings)")
return []
}
return self.flatMap { (anEntry) -> String? in
guard let temp = anEntry.key as? String else { return nil }
return temp }
}
}
And I'll get all the keys later using this.
let componentsArray = dict.allKeys()
// Old version (for history)
let keys = dictionary.keys.map { $0 }
let keys = dictionary?.keys.map { $0 } ?? [T]()
// New more explained version for our ducks
extension Dictionary {
var allKeys: [Dictionary.Key] {
return self.keys.map { $0 }
}
}