If I have the following array and I want to create a string array containing the door prizes by mapping the mysteryDoors array as keys for the dictionary, and get the corresponding values into a new array.
Thus I would get a string array of ["Gift Card", "Car", "Vacation"] how can I do that?
let mysteryDoors = [3,1,2]
let doorPrizes = [
1:"Car", 2: "Vacation", 3: "Gift card"]
You can map() each array element to the corresponding value in
the dictionary. If it is guaranteed that all array elements are
present as keys in the dictionary then you can do:
let mysteryDoors = [3, 1, 2]
let doorPrizes = [ 1:"Car", 2: "Vacation", 3: "Gift card"]
let prizes = mysteryDoors.map { doorPrizes[$0]! }
print(prizes) // ["Gift card", "Car", "Vacation"]
To avoid a runtime crash if a key is not present, use
let prizes = mysteryDoors.flatMap { doorPrizes[$0] }
to ignore unknown keys, or
let prizes = mysteryDoors.map { doorPrizes[$0] ?? "" }
to map unknown keys to a default string.
If you have to use map, then it would look something like the following:
let array = mysteryDoors.map { doorPrizes[$0] }
After re-reading the Apple Doc example code and changing it to what I need. I believe this is it (Almost). Unfortunately it is now in string format with new lines...
let myPrizes = doorPrizes.map { (number) -> String in
var output = ""
output = mysteryDoors[number]!
return output;
}
Related
The problem with the ECMA standard for sort of Object.keys() is known:
Object.keys() handle all keys with integer (example: 168), including integer as strings (example: "168"), as a integer. The result is, both are the same (168 === "168"), and overwrite itself.
var object = {};
object["168"] = 'x';
object[168] = 'y';
Object.keys(object); // Array [ "168" ]
object[Object.keys(object)]; // "y"
Interestingly, all keys (including pure integer keys) are returned as a string.
The ecma262 wrote about this: All keys will be handle as a integer, expect the key is a String but is not an array index.
https://tc39.es/ecma262/#sec-ordinaryownpropertykeys
That should tell us: 168 === "168". A toString() do not solve the problem.
var object = {};
object[[3].toString()] = 'z';
object[[1].toString()] = 'x';
object[[2].toString()] = 'y';
Object.keys(object);
// Array(3) [ "1", "2", "3" ]
Paradoxically, in this case, only integer apply as "enumerable" (it's ignoring array.sort(), that sort also strings with letters.).
My question about this is simple: How can i prevent the sort function in Object.keys()? I have testet the Object.defineProperties(object, 1, {value: "a", enumerable: true/false}), but that mean not realy enumerable in the case of integer or string or integer-like string. It means only should it be counted with or not. It means "counted" like omit (if it false), not "enumerabled" like ascending or descending.
A answere like that is not a good answer: Please use only letters [a-zA-Z] or leastwise a letter at the first position of keyword.
What I want: That the keys are not sorted, but output in the order in which they were entered, whether integer, string or symbol.
Disclaimer: Please solutions only in JavaScript.
Javascript Objects are unordered by their nature. If you need an ordered object-like variable I would suggest using a map.
To achieve what you're looking for with a map instead of object you'd do something like the below:
var map1 = new Map();
map1.set("123", "c");
map1.set(123, "b");
var iterator1 = map1.keys();
var myarray = [];
for (var i = 0; i < map1.size; i++) {
myarray.push(iterator1.next().value);
}
console.log(myarray);
// Array ["123", 123]
Unfortunately it's not compatible with IE and I'm not sure how else you could achieve what you need without it. A quick Google did return something about jQuery maps, though.
If you don't want to use jQuery and still need to support IE some points are below:
Is there anything stopping you using an array rather than JS object to store the data you need? This will retain the order per your requirements unlike objects. You could have an object entry in each iteration which represents the key then use a traditional foreach to obtain them as an array. I.e.
The array:
var test_array = [
{key: 123, value: 'a value here'},
{key: "123", value: 'another value here'}
];
// console.log(test_array);
Getting the keys:
var test_array_keys = [];
test_array.forEach(function(obj) { test_array_keys.push(obj['key']); } );
// console.log(test_array_keys);
Then if you needed to check whether the key exists before adding a new entry (to prevent duplicates) you could do:
function key_exists(key, array)
{
return array.indexOf(key) !== -1;
}
if(key_exists('12345', test_array_keys))
{
// won't get here, this is just for example
console.log('Key 12345 exists in array');
}
else if(key_exists('123', test_array_keys))
{
console.log('Key 123 exists in array');
}
Would that work? If not then the only other suggestion would be keeping a separate array alongside the object which tracks the keys and is updated when an entry is added or removed to/from the object.
Object Keys sorted and store in array
First Creating student Object. then sort by key in object,last keys to store in array
const student={tamil:100, english:55, sci:85,soc:57}
const sortobj =Object.fromEntries(Object.entries(student).sort())
console.log(Object.keys(sortobj))
use map instead of an object.
let map = new Map()
map.set("a", 5)
map.set("d", 6)
map.set("b", 12)
to sort the keys (for example, to update a chart data)
let newMap = new Map([...map.entries()].sort())
let keys = Array.from(newMap.keys()) // ['a','b','d']
let values = Array.from(newMap.values()) // [5,12,6]
Apologize for a complete newbie question. This was the original array of Strings I wrote:
let fruit = ["apple1.jpg", "apple2.jpg", "apple3.jpg", ..... "apple10.jpg"]
First, I made a function in a separate Swift file (attached to the project) to replace above array, as the array's content might be changed based on several input factors later:
class Fruits {
let fruit = "apple"
func fruitName() -> [String] {
let arrayA = (1...10).map({ "\(fruit)\($0).jpg" })
return arrayA
}
}
}
This is everything written on Fruits.swift file. And then, back to original file, I wanted to replace the original let fruit = ["", "", ...] to something like let fruit = Fruits.fruitName() - by loading the returned arrayA. But it was a bit confusing to understand how to use returned String Array values in a different file, inside of a different Class bracket. I tried something like let fruits = Fruits(), let fruit = fruits.fruitName(), etc but it doesn't seem to successfully replace the original array code. I still need to create the constant let fruit = part. Is there any way to load the returned value in a separate file? Much appreciated. <3
If you want a property of a class to be directly accessible from anywhere in your code, you can make it static:
class Fruits {
static let fruit = "apple"
static func fruitName() -> [String] {
let arrayA = (1...10).map({ "\(fruit)\($0).jpg" })
return arrayA
}
}
// usage:
let fruits = Fruits.fruitName()
Depending on your specific situation, you could even not have a class and have a global function that takes the fruit as a parameter:
func fruitNames(fruit: String) -> [String] {
let arrayA = (1...10).map({ "\(fruit)\($0).jpg" })
return arrayA
}
// usage:
let fruits = fruitNames(fruit: "apple")
This is a fundamental thing that I should know but don't know at a deep level and therefore find confusing. Dictionaries seem to be unordered list of keys and values. I want to create an ordered list of keys and values so that I can sort and otherwise keep track of order. I think this means I have to convert the dictionary into a multi-dimensional Array that has the key and value and also an index value ie 0,1,2,3 etc.
If my dictionary looks like the following:
var myScores = [String: Float]()
myScores = ["player1":22,"player2":33]
How do I convert it into an Array where player1:22 is the first element and player2:33 is the second element?
Edit:
Alternative without creating struct is to create an empty array of dictionaries in the form of your dictionary and then append your dictionary to the array.
var myArray = [[String: Float]]()//note double brackets
propArray.append(myScores)
What you want is an array of structs.
struct Score {
let playerName: String
let score: Int
}
let scores = [Score(playerName: "player1", score: 22),
Score(playerName: "player2", score: 33),
]
let sortedScores = scores.sorted(by: { $0.playerName < $1.playerName })
To get key-value pairs out of a dictionary is straightforward, though it forces you to work with tuples, which are not a particularly friendly type. Even so, it's done this way:
let sortedScores = myScores.sorted { $0.key < $1.key }
That will create:
[(key: "player1", value: 22.0), (key: "player2", value: 33.0)]
Or
for (name, score) in myScores.sorted(by: { $0.key < $1.key }) {
print(name, score)
}
You can keep the dictionary as-is. One possible solution is to create an array that contains just the keys in the desired order. Then you can iterate the key array and access the elements of the dictionary.
var myScores: [String:Float] = ["player1":22, "player2":33]
var myPlayers = myScores.keys.sorted()
for player in myPlayers {
let score = myScores[player]
}
This works when you want to show the data in some particular order, such as in a table view.
I want to implement a multiple click in my Shinobi DataGrid. I have a grid which have array
( ["1", "32", and more] )
If I click the grid I put it into new Array self.arrayNr.append(currNr).
But I want to check and remove if currNr is already exist in arrayNr it is will be remove from the arrayNr.
I'm new and using Swift 3. I read some question regarding with my question like this and this but it's not working. I think the Swift 2 is simpler than Swift 3 in handling for String. Any sugesstion or answer will help for me?
You can use index(of to check if the currNrexists in your array. (The class must conform to the Equatable protocol)
var arrayNr = ["1", "32", "100"]
let currNr = "32"
// Check to remove the existing element
if let index = arrayNr.index(of: currNr) {
arrayNr.remove(at: index)
}
arrayNr.append(currNr)
Say you have an array of string, namely type [String]. Now you want to remove a string if it exists. So you simply need to filter the array by this one line of code
stringArray= stringArray.filter(){$0 != "theValueThatYouDontWant"}
For example, you have array like this and you want to remove "1"
let array = ["1", "32"]
Simply call
array = array.filter(){$0 != "1"}
Long Solution
sampleArray iterates over itself and removes the value you are looking for if it exists before exiting the loop.
var sampleArray = ["Hello", "World", "1", "Again", "5"]
let valueToCheck = "World"
for (index, value) in sampleArray.enumerated() {
if value == valueToCheck && sampleArray.contains(valueToCheck) {
sampleArray.remove(at: index)
break
}
}
print(sampleArray) // Returns ["Hello", "1", "Again", "5"]
Short Solution
sampleArray returns an array of all values that are not equal to the value you are checking.
var sampleArray = ["Hello", "World", "1", "Again", "5"]
let valueToCheck = "World"
sampleArray = sampleArray.filter { $0 != valueToCheck }
print(sampleArray) // Returns ["Hello", "1", "Again", "5"]
An NSSet can be converted to Array using set.allObjects() but there is no such method in the new Set (introduced with Swift 1.2). It can still be done by converting Swift Set to NSSet and use the allObjects() method but that is not optimal.
You can create an array with all elements from a given Swift
Set simply with
let array = Array(someSet)
This works because Set conforms to the SequenceType protocol
and an Array can be initialized with a sequence. Example:
let mySet = Set(["a", "b", "a"]) // Set<String>
let myArray = Array(mySet) // Array<String>
print(myArray) // [b, a]
In the simplest case, with Swift 3, you can use Array's init(_:) initializer to get an Array from a Set. init(_:) has the following declaration:
init<S>(_ s: S) where S : Sequence, Element == S.Iterator.Element
Creates an array containing the elements of a sequence.
Usage:
let stringSet = Set(arrayLiteral: "car", "boat", "car", "bike", "toy")
let stringArray = Array(stringSet)
print(stringArray)
// may print ["toy", "car", "bike", "boat"]
However, if you also want to perform some operations on each element of your Set while transforming it into an Array, you can use map, flatMap, sort, filter and other functional methods provided by Collection protocol:
let stringSet = Set(["car", "boat", "bike", "toy"])
let stringArray = stringSet.sorted()
print(stringArray)
// will print ["bike", "boat", "car", "toy"]
let stringSet = Set(arrayLiteral: "car", "boat", "car", "bike", "toy")
let stringArray = stringSet.filter { $0.characters.first != "b" }
print(stringArray)
// may print ["car", "toy"]
let intSet = Set([1, 3, 5, 2])
let stringArray = intSet.flatMap { String($0) }
print(stringArray)
// may print ["5", "2", "3", "1"]
let intSet = Set([1, 3, 5, 2])
// alternative to `let intArray = Array(intSet)`
let intArray = intSet.map { $0 }
print(intArray)
// may print [5, 2, 3, 1]
I created a simple extension that gives you an unsorted Array as a property of Set in Swift 4.0.
extension Set {
var array: [Element] {
return Array(self)
}
}
If you want a sorted array, you can either add an additional computed property, or modify the existing one to suit your needs.
To use this, just call
let array = set.array
ADDITION :
Swift has no DEFINED ORDER for Set and Dictionary.For that reason you should use sorted() method to prevent from getting unexpected results such as your array can be like ["a","b"] or ["b","a"] and you do not want this.
TO FIX THIS:
FOR SETS
var example:Set = ["a","b","c"]
let makeExampleArray = [example.sorted()]
makeExampleArray
Result: ["a","b","c"]
Without sorted()
It can be:
["a","b","c"] or ["b","c","a",] or ["c","a","b"] or ["a","c","b"] or ["b","a","c"] or ["c","b","a"]
simple math : 3! = 6
The current answer for Swift 2.x and higher (from the Swift Programming Language guide on Collection Types) seems to be to either iterate over the Set entries like so:
for item in myItemSet {
...
}
Or, to use the "sorted" method:
let itemsArray = myItemSet.sorted()
It seems the Swift designers did not like allObjects as an access mechanism because Sets aren't really ordered, so they wanted to make sure you didn't get out an array without an explicit ordering applied.
If you don't want the overhead of sorting and don't care about the order, I usually use the map or flatMap methods which should be a bit quicker to extract an array:
let itemsArray = myItemSet.map { $0 }
Which will build an array of the type the Set holds, if you need it to be an array of a specific type (say, entitles from a set of managed object relations that are not declared as a typed set) you can do something like:
var itemsArray : [MyObjectType] = []
if let typedSet = myItemSet as? Set<MyObjectType> {
itemsArray = typedSet.map { $0 }
}
call this method and pass your set
func getArrayFromSet(set:NSSet)-> NSArray {
return set.map ({ String($0) })
}
Like This :
var letters:Set = Set<String>(arrayLiteral: "test","test") // your set
print(self.getArrayFromSet(letters))