I've only basic knowledge in Swift.
I want to change var dataSource:[[CustomModel?]]? into [CustomModel].
I tried following Methods
let flat = dataSource.reduce([],+)
let flat = dataSource.flatMap { $0 }
let flat = dataSource.compactMap{ $0 }
let flat = dataSource.Array(dataSource.joined())
I'm getting error
Cannot convert value of type '[FlattenSequence<[[CustomModel?]]>.Element]' (aka 'Array<Optional< CustomModel >>') to expected argument type '[CustomModel]'
You need to flat the nested array first using flatMap{}, then in order to get the non-optional value use compactMap{}. Suppose the input array is [[Int?]]
let value:[Int] = dataSource.flatMap{$0}.compactMap{ $0 } //Correct
The other option will give an error -
let value:[Int] = dataSource.flatMap{ $0 } ?? [] //Error
//Correct
//Wrong
You can try
var arr:[CustomModel] = dataSource?.flatMap { $0 } ?? []
Also
var arr:[CustomModel] = dataSource?.flatMap { $0 }.compactMap{ $0 } ?? []
Related
I have an array:
let arr = ["Ivan Ivanov", "Bogdan Bogdanov", "Georgi Milchev", "Bogdan Petkov", "Vladimir Zahariev"]
let name = "Bogdan"
Search if array contains(name) and append the result to the new array without loop.
So new array have to be ["Bogdan Bogdanov", "Bogdan Petkov"]
Trying with: if arr.contains(where: {$0 == name}) { newArray.append($0) }
but it's not working. Error: Anonymous closure argument not contained in a closure
You need
let res = arr.compactMap { $0.contains(name) ? $0.components(separatedBy: " ").last! : nil }
I'm Using Swift2.0+, SwiftyJSON, Alamofire
I Got the Value let stringJSON:JSON = ["a1","a2","a3"] from Server
But If I Check stringJSON[0],Then it's null
When I debugPrint(stringJSON), Then it's ["a1","a2","a3"]
How Can I got the value stringJSON[0] //"a1" ?
Do I Have To Convert From JSON To Another?
The correct syntax is
let stringJSON:JSON = ["a1","a2","a3"]
if let firstValue = stringJSON.array?.first {
print(firstValue) // a1
}
Update
Since the value actually contains this string "[\"a1\/a1\",\"a2\/a2\",\"a3\"]" and you cannot fix this on the server side here it is a workaround.
if let words = stringJSON.string?.characters.dropFirst().dropLast().split(",").map(String.init) {
let word = String(words[0].characters.dropFirst().dropLast())
print(word) // a1
}
if let x = stringJSON[0].string{
print(x)
}
Since the server is not returning an Array, but a String, you need to convert that into an Array of Strings like this:
let string = stringJSON.string
let array = string.stringByReplacingOccurrencesOfString("[", withString: "")
.stringByReplacingOccurrencesOfString("]", withString: "")
.stringByReplacingOccurrencesOfString("\"", withString: "")
.componentsSeparatedByString(",")
stringJSONIf it is a string type, you can like this to solve:
extension String {
var parseJSONString: AnyObject? {
var any: AnyObject?
let data = self.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)
do{
any = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableContainers)
}catch let error as NSError{
print("error: \(error)")
}
return any
}
and use it like this:
let strArr = stringJSON.stringvalue.parseJSONString as! Array<String>
I am trying to create an array of words from a string object retrieved from Parse. The object retrieved looks like this:
Then this line of code gives this.
let joinedWords = object["Words"] as! String
How do I convert joinedWords to an Array?
If you don't care about the order, you can use flatMap on the set:
var mySet = Set<String>()
for index in 1...5 {
mySet.insert("testwords\(index)")
}
let myArray = mySet.flatMap { $0 }
print(myArray) // "["testwords5", "testwords3", "testwords4", "testwords2", "testwords1"]"
If you want the list sorted alphabetically, you can make your array a var and use sortInPlace()
var myArray = mySet.flatMap { $0 }
myArray.sortInPlace()
print(myArray) // "["testwords1", "testwords2", "testwords3", "testwords4", "testwords5"]"
If object["Words"] is AnyObject, you will have to unwrap it.
if let joinedWordsSet = object["Words"] as? Set<String> {
var joinedWordsArray = joinedWordsSet.flatMap { $0 }
myArray.sortInPlace()
print(myArray)
}
Swift 3 note: sortInPlace() has been renamed sort().
Many thanks to #JAL for so much time on chat to solve this one. This is what we came up with. Its a bodge and no doubt there is a better way!
When uploading to Parse save the set as an array.
let wordsSet = (wordList?.words?.valueForKey("wordName"))! as! NSSet
let wordsArray = Array(wordsSet)
Then it saves to Parse - looking like a set, not an array or a dictionary.
let parseWordList = PFObject(className: "WordList")
parseWordList.setObject("\(wordsArray)", forKey: "Words")
parseWordList.saveInBackgroundWithBlock { (succeeded, error) -> Void in
if succeeded {
// Do something
} else {
print("Error: \(error) \(error?.userInfo)")
}
}
Then you can drop the [ ] off the string when its downloaded from Parse, and remove the , and add some "" and voila, there is an array that can be used e.g. to add to CoreData.
var joinedWords = object["Words"] as! String
joinedWords = String(joinedWords.characters.dropFirst())
joinedWords = String(joinedWords.characters.dropLast())
let joinedWordsArray = joinedWords.characters.split() {$0 == ","}.map{ String($0) } // Thanks #JAL!
What woudl be a simple way to reduce a string like AAA:111;BBB:222;333;444;CCC:555 to a dictionary in Swift. I have the following code:
var str = "AAA:111;BBB:222;333;444;CCC:555"
var astr = str.componentsSeparatedByString(";").map { (element) -> [String:String] in
var elements = element.componentsSeparatedByString(":")
if elements.count < 2 {
elements.insert("N/A", atIndex: 0)
}
return [elements[0]:elements[1]]
}
The code above produces an Array of Dictionaries:
[["A": "111"], ["BBB": "222"], ["UKW": "333"], ["UKW": "444"], ["CCC": "555"]]
I want it to produce
["A": "111", "BBB": "222", "UKW": "333", "UKW": "444", "CCC": "555"]
but no mater what I try, since i call the map function on an Array it seems impossible to convert the nature of the map function's result.
NOTE: The dictionary in string format is described as either having KEY:VALUE; format or VALUE; format, in which case the mapping function will add the "N/A" as being the key of the unnamed value.
Any help on this matter is greatly appreciated.
Your map produces an array of dictionaries. When you want to combine them into 1, that's a perfect job for reduce:
func + <K,V>(lhs: Dictionary<K,V>, rhs: Dictionary<K,V>) -> Dictionary<K,V> {
var result = Dictionary<K,V>()
for (key, value) in lhs {
result[key] = value
}
for (key, value) in rhs {
result[key] = value
}
return result
}
var str = "AAA:111;BBB:222;333;444;CCC:555"
var astr = str
.componentsSeparatedByString(";")
.reduce([String: String]()) {
aggregate, element in
var elements = element.componentsSeparatedByString(":")
if elements.count < 2 {
elements.insert("N/A", atIndex: 0)
}
return aggregate + [elements[0]:elements[1]]
}
print(astr)
Swift has no default operator to "combine" two Dictionaries so you have to define one. Note that the + here is not commutative: dictA + dictB != dictB + dictA. If a key exist in both dictionaries, the value from the second dictionary will be used.
This is a work for reduce:
let str = "AAA:111;BBB:222;333;444;CCC:555"
let keyValueStrings = str.componentsSeparatedByString(";")
let dictionary = keyValueStrings.reduce([String: String]()) {
aggregate, element in
var newAggregate = aggregate
let elements = element.componentsSeparatedByString(":")
let key = elements[0]
// replace nil with the value you want to use if there is no value
let value = (elements.count > 1) ? elements[1] : nil
newAggregate[key] = value
return newAggregate
}
print(dictionary)
You can also make aggregate mutable directly:
let dictionary = keyValueStrings.reduce([String: String]()) {
(var aggregate: [String: String], element: String) -> [String: String] in
let elements = element.componentsSeparatedByString(":")
let key = elements[0]
// replace nil with the value you want to use if there is no value
let value = (elements.count > 1) ? elements[1] : nil
aggregate[key] = value
return aggregate
}
This is a functional approach, but you can achieve the same using a for iteration.
The reason this is happening is because map can only return arrays. If you are using this method to parse your string, then you need to convert it to a dictionary after.
var newDict = [String:String]()
for x in astr {
for (i, j) in x {
newDict[i] = j
}
}
The current issue with your code is that map function iterates over array containing [["key:value"],["key:value"]..] and you separate it again. But it returns ["key":"value"] which you then add to your array.
Instead you can add elements[0]:elements[1] directly to a locally kept variable which will fix your problem. Something like
finalVariable[elements[0]] = elements[1]
I would like to know how can i fill my label from an Array
func metaDataUpdated(metaData : NSString){
var listItems: NSArray = [metaData.componentsSeparatedByString(";")]
if ([listItems.count] > 0){
println([listItems.objectAtIndex(0)])
titleSong.text = [listItems.objectAtIndex(0)]
}
}
I don't really know how to convert an array to string.
Direct conversion to Swift:
func metaDataUpdated(metaData : String) {
let listItems = metaData.componentsSeparatedByString(";")
if listItems.count > 0 {
print(listItems[0])
titleSong.text = listItems[0]
}
}
Nicer Swift:
func metaDataUpdated(metaData : String) {
let listItems = metaData.componentsSeparatedByString(";")
if let first = listItems.first {
print(first)
titleSong.text = first
}
}
Even nicer Swift, without using Foundation and without the function needing to get every component separated by ";", but only the first one (recommended):
func metaDataUpdated(metaData : String) {
if let index = metaData.characters.indexOf(";") {
let first = metaData[metaData.startIndex ..< index]
print(first)
titleSong.text = first
}
}
you cannot assign NSArray to NSString therefore you need to cast the value of this first index into a string
change this
titleSong.text = [listItems.objectAtIndex(0)]
to
titleSong.text = "\(listItems.objectAtIndex(0))"
or
titleSong.text = listItems[0] as! String
and also change this line to ([listItems.count > 0]) to (listItems.count > 0)
your code will look like this:
Note this not obj-c so remove all []
func metaDataUpdated(metaData : NSString){
var listItems: NSArray = metaData.componentsSeparatedByString(";")
if (listItems.count > 0)
{
println(listItems.objectAtIndex(0))
titleSong.text = listItems.objectAtIndex(0) as! String
}
}
Better use Swift types and objects now: Array instead of NSArray, Dictionary instead of NSDictionary, etc.
func metaDataUpdated(metaData : NSString) {
var listItems = metaData.componentsSeparatedByString(";")
if listItems.count > 0 {
print(listItems[0])
titleSong.text = listItems[0]
}
}
Here componentsSeparatedByString returns an array of strings: [String]. We then use simple index subscripting to retrieve its first value.
Note: I suppose you were trying to adapt code from Objective-C because your example was ridden with [] everywhere...
Put your to string item in "\\()".
For instance:
titleSong.text = "\\([listItems.objectAtIndex(0)])"
Not sure you need the [] brackets though