I am trying to access the value from a dictionary using a random number, but I am lost, can someone please guide?
Here is what I have:
var themes = ["Halloween": "😈💀🤡👻🤖👽", "Sports": "🏉🏓⛳️⚽️🎳🎱" , "Faces": "😀😍😨🤗😤🤤", "Animal": "🦓😼😺😿🙀🙈"]
// This Does not work for some reason?
lazy var themeRandomNumber = themes.count.arc4random
lazy var currentTheme = themes[themeRandomNumber]
//Cannot subscript a value of type[String : String]' with an index of type 'Int'
This makes sense since, I am trying to access the key using an Int when it is obviously a String, but not sure how to proceed?
lazy var currentEmoji = themes[currentTheme]
extension Int{
var arc4random: Int{
if self > 0 {
return Int(arc4random_uniform(UInt32(self)))
} else if self < 0 {
return -Int(arc4random_uniform(UInt32(abs(self))))
} else {
return 0
}
}
}
Just replace
lazy var currentEmoji = themes[currentTheme]
with
var currentTheme = themes.randomElement()
print(currentTheme?.value) //Optional("🏉🏓⛳️⚽️🎳🎱")
print(currentTheme?.key) //Optional("Sports")
Here randomElement is new property which you can use to get random element.
Because you're not accessing the key of your dictionary, you need to select "Halloween", "Sports", "Faces" or "Animal" - your themes dict's keys.
You can use some custom mapping method with Int.random(in: 0...3) or a Keys enum conforming to CaseIterable, and then you need to select a random character (emoji) in the String for your given Key (via a random number in the range 0..<string.length).
EDIT
With Swift 4.2+ (Xcode 10) you can use randomElement():
var themes = ["Halloween": "😈💀🤡👻🤖👽", "Sports": "🏉🏓⛳️⚽️🎳🎱" , "Faces": "😀😍😨🤗😤🤤", "Animal": "🦓😼😺😿🙀🙈"]
var randomEmoji = themes.randomElement()?.value.randomElement()
Related
I have an array like:-
var arrayData : Array<Dictionary<String, [BottleModel]>> = []
Bottle model :-
class BottleModel: NSObject {
var name : String
var price : Int
var reviews : Int
var category : String
var quantity : String
var id : String
var shopData : ShopModel
}
I want filtered array where price is > 2000
I tried let searchByInts = arrayData.filter({m in m.price < 200})
but getting below error:
Contextual closure
type '(Dictionary) -> Bool' expects 1 argument,
but 0 were used in closure body
How to filter such kind of array based on price
Working code:
let searchByInts = arrayData.filter { $0.values.contains { $0.contains { $0.price > 2000 } } }
By the way please write the following using literals:
var arrayData : [[String : [BottleModel]]] = []
Still no idea if that is what you actually want because your goal is very unclear. You have an array of dictionaries of arrays which actually contain the values you want to filter out. If a BottleModel costs more than 2000 do you want to keep the entire array it is contained in and the dictionary that array is in? You might want to map the entire data into one flat array before or after filtering.
Alternative using flatMap:
let flat = arrayData.flatMap { $0.values.flatMap { $0 } }
let searchByInts2 = flat.filter { $0.price < 200 } // or some other criteria
I have this class
class InboxInterests {
var title = ""
var eventID = 0
var count = ""
var added = 0
init(title : String, eventID : NSInteger, count: String, added : NSInteger) {
self.title = title
self.eventID = eventID
self.count = count
self.added = added
}
}
And i use it like this
var array: [InboxInterests] = [InboxInterests]()
Add item
let post = InboxInterests(title: "test",eventID : 1, count: "test", added: 0)
self.array.append(post)
I want to find the index by eventID key and change the value of added key in the same index
How is that possible?
For me, the above answer did not work. So, what I did was first find the index of the object that I want to replace then using the index replace it with the new value
if let row = self.upcoming.index(where: {$0.eventID == id}) {
array[row] = newValue
}
In Swift 5.0:
if let row = self.upcoming.firstIndex(where: {$0.eventID == id}) {
array[row] = newValue
}
Since you are using a class, use filter and first to find the value:
array.filter({$0.eventID == id}).first?.added = value
In this you:
filter the array down to elements that match the event ID
pick the first result, if any
then set the value
This works since classes are pass by reference. When you edit the return value from array.filter({$0.eventID == id}).first?, you edit the underlying value. You'll need to see the answers below if you are using a struct
EDIT: In Swift 3 you can save yourself a couple of characters
array.first({$0.eventID == id})?.added = value
EDIT: Swift 4.2:
array.first(where: { $0.eventID == id })?.added = value
array.filter {$0.eventID == id}.first?.added = value
The filter operator is not the best in this case, it works for some of you because classes are passed by reference.
Explanation: (You can copy the following code in a playground if you want to verify it).
class Book {
let id: Int
var title = "default"
init (id: Int) {
self.id = id
}
}
var arrayBook = [Book]()
arrayBook.append(Book(id: 0))
arrayBook.append(Book(id:1))
arrayBook.forEach { book in
print(book.title)
}
arrayBook.filter{ $0.id == 1 }.first?.title = "modified"
arrayBook.forEach { book in
print(book.title)
}
Arrays are copied by value not reference, so when you are using filter you are creating a new array (different than the initial), but when you modify the new one, the initial one gets modified too because both are pointing to the same class (classed are passed by reference), so after the filter your array will have changed and the new one gets deallocated. So in this case it will print "default", "default" and then "default, "modified".
What happens if you change class for struct, the value will be passed by value not reference so you will have 2 arrays in memory with different values, so if you go through arrayBooks again it will print before the filter "default","default", and then "default", "default" again. Because when you are using the filter you are creating and modifying a new array that will get deallocated if you do not store it).
The solution is using map, creating a new array with all the values but with the modified items or fields that we want and then replace our array with the new one. This will print "default", "default" before the map, and then "default", "modified"
This will work with structs, classes and everything that you want :).
struct Book {
let id: Int
var title = "default"
init (id: Int) {
self.id = id
}
}
var arrayBook = [Book]()
arrayBook.append(Book(id: 0))
arrayBook.append(Book(id:1))
arrayBook.forEach { book in
print(book.title)
}
arrayBook = arrayBook.map{
var mutableBook = $0
if $0.id == 1 {
mutableBook.title = "modified"
}
return mutableBook
}
arrayBook.forEach { book in
print(book.title)
}
array = array.map { $0.eventID == id ? newValue : $0 }
If you conform your class to Equatable then this would work:
extension Array where Element: Equatable {
#discardableResult
public mutating func replace(_ element: Element, with new: Element) -> Bool {
if let f = self.firstIndex(where: { $0 == element}) {
self[f] = new
return true
}
return false
}
}
Use like this:
array.replace(prev, with: new)
I am trying to use a list that is a value for a dictionary key/pair set, and this dictionary is itself a value in a key/pair set in a dictionary. To explain, this is how I initialize it.
var dictOfEvents = [Int: [Int: [PFObject]]]()
I am trying to add events to the list, with the inner dictionary's key being the day of month and the outer one being the month. For example, an event on May 1 would be:
dictOfEvents[5:[1:[ListOfEvents]]
Where ListOfEvents is an array of PFObjects. Before I added the month functionality, and thus the outer dictionary, the way I added new events was:
` self.dictOfEvents[components.day] = [event]
But now, when I try to extend this with:
self.dictOfEvents[components.month]?[components.day]! = [event]
It does not work. Any explanation on how to create new event lists and access this double layer dictionary would be greatly appreciated.
(Note: I don't know where to put the ! and the ? in the last piece of code so please excuse me if I made a mistake.)
Here is what I think could be a good use of optionals in your case (and should respond to your question):
var dic: [Int: [Int: [String]]] = [:]
dic[5] = [1:["Hello", "World"]]
if let list = dic[5]?[1] {
// your list exist and you can safely use it
for item in list {
println(item)
}
}
I just used String instead of PFObject.
A different approach could be:
/*
Define a struct to encapsulate your Month and Day
Make it Hashable so that you can use it as Dictionary key
*/
public struct MonthDay: Hashable {
let month: Int
let day: Int
public var hashValue: Int { return month * 100 + day }
}
public func ==(lhs: MonthDay, rhs: MonthDay) -> Bool {
return lhs.month == rhs.month && lhs.day == rhs.day
}
var dictOfEvents = [MonthDay :[String]]()
let aMonthAndDay = MonthDay(month: 5, day: 1)
dictOfEvents[aMonthAndDay] = ["Hello", "World"]
if let list = dictOfEvents[aMonthAndDay] {
// your list exist and you can safely use it
for item in list {
println(item)
}
}
U can simple change:
self.dictOfEvents[components.month]?[components.day]! = [event]
to :
self.dictOfEvents[components.month]![components.day]! = [event]
Because Dictionary has subscript, Dictionary? doesn't have subscript.
if U try add Events to Dictionary. I suggest to use this:
var dictOfEvents = [Int: [Int: [PFObject]]]()
var dictOfDayEvents = [Int:[PFObject]]()
dictOfDayEvents.updateValue([PFObject()], forKey: 1)
dictOfEvents.updateValue(dictOfDayEvents, forKey: 5)
is there a possibility to get an object from an array with an specific property? Or do i need to loop trough all objects in my array and check if an property is the specific i was looking for?
edit: Thanks for given me into the correct direction, but i have a problem to convert this.
// edit again: A ok, and if there is only one specific result? Is this also a possible method do to that?
let imageUUID = sender.imageUUID
let questionImageObjects = self.formImages[currentSelectedQuestion.qIndex] as [Images]!
// this is working
//var imageObject:Images!
/*
for (index, image) in enumerate(questionImageObjects) {
if(image.imageUUID == imageUUID) {
imageObject = image
}
}
*/
// this is not working - NSArray is not a subtype of Images- so what if there is only 1 possible result?
var imageObject = questionImageObjects.filter( { return $0.imageUUID == imageUUID } )
// this is not working - NSArray is not a subtype of Images- so what if there is only 1 possible result?
You have no way to prove at compile-time that there is only one possible result on an array. What you're actually asking for is the first matching result. The easiest (though not the fastest) is to just take the first element of the result of filter:
let imageObject = questionImageObjects.filter{ $0.imageUUID == imageUUID }.first
imageObject will now be an optional of course, since it's possible that nothing matches.
If searching the whole array is time consuming, of course you can easily create a firstMatching function that will return the (optional) first element matching the closure, but for short arrays this is fine and simple.
As charles notes, in Swift 3 this is built in:
questionImageObjects.first(where: { $0.imageUUID == imageUUID })
Edit 2016-05-05: Swift 3 will include first(where:).
In Swift 2, you can use indexOf to find the index of the first array element that matches a predicate.
let index = questionImageObjects.indexOf({$0.imageUUID == imageUUID})
This is bit faster compared to filter since it will stop after the first match. (Alternatively, you could use a lazy sequence.)
However, it's a bit annoying that you can only get the index and not the object itself. I use the following extension for convenience:
extension CollectionType {
func find(#noescape predicate: (Self.Generator.Element) throws -> Bool) rethrows -> Self.Generator.Element? {
return try indexOf(predicate).map({self[$0]})
}
}
Then the following works:
questionImageObjects.find({$0.imageUUID == imageUUID})
Yes, you can use the filter method which takes a closure where you can set your logical expression.
Example:
struct User {
var firstName: String?
var lastName: String?
}
let users = [User(firstName: "John", lastName: "Doe"), User(firstName: "Bill", lastName: "Clinton"), User(firstName: "John", lastName: "Travolta")];
let johns = users.filter( { return $0.firstName == "John" } )
Note that filter returns an array containing all items satisfying the logical expression.
More info in the Library Reference
Here is a working example in Swift 5
class Point{
var x:Int
var y:Int
init(x:Int, y:Int){
self.x = x
self.y = y
}
}
var p1 = Point(x:1, y:2)
var p2 = Point(x:2, y:3)
var p3 = Point(x:1, y:4)
var points = [p1, p2, p3]
// Find the first object with given property
// In this case, firstMatchingPoint becomes p1
let firstMatchingPoint = points.first{$0.x == 1}
// Find all objects with given property
// In this case, allMatchingPoints becomes [p1, p3]
let allMatchingPoints = points.filter{$0.x == 1}
Reference:
Trailing Closure
Here is other way to fetch particular object by using object property to search an object in array.
if arrayTicketsListing.contains({ $0.status_id == "2" }) {
let ticketStatusObj: TicketsStatusList = arrayTicketsListing[arrayTicketsListing.indexOf({ $0.status_id == "2" })!]
print(ticketStatusObj.status_name)
}
Whereas, my arrayTicketsListing is [TicketsStatusList] contains objects of TicketsStatusList class.
// TicketsStatusList class
class TicketsStatusList {
internal var status_id: String
internal var status_name: String
init(){
status_id = ""
status_name = ""
}
}
var sourceEntries: [Entry] = [entry1, ..., entry14]
var myDict: Dictionary<String, [Entry]> = [:]
for entry in sourceEntries {
if var array = myDict[entry.attribute1] { theArray.append(entry) }
else { myDict[entry.attribute1] = [entry] }
}
I am intending to create a Dictionary, which matches all the objects of the struct "Eintrag" with the same attribute from the source-Array "alleEinträge" to a String containing the value of the shared attribute. For some reason my final Dictionary just matches Arrays of one element to the Strings, although some Arrays ought to contain up to four elements.
The problem is that the array is passed by value (i.e. "copied"), so the array you are writing to when you say array.append is not the array that is "inside" the dictionary. You have to write back into the dictionary explicitly if you want to change what's in it.
Try it in a simple situation:
var dict = ["entry":[0,1,2]]
// your code
if var array = dict["entry"] { array.append(4) }
// so what happened?
println(dict) // [entry: [0, 1, 2]]
As you can see, the "4" never got into the dictionary.
You have to write back into the dictionary explicitly:
if var array = dict["entry"] { array.append(4); dict["entry"] = array }
FURTHER THOUGHTS: You got me thinking about whether there might be a more elegant way to do what you're trying to do. I'm not sure whether you will think this is "more elegant", but perhaps it has some appeal.
I will start by setting up a struct (like your Entry) with a name attribute:
struct Thing : Printable {
var name : String
var age : Int
var description : String {
return "{\(self.name), \(self.age)}"
}
}
Now I will create an array like your sourceEntries array, where some of the structs share the same name (like your shared attribute attribute1):
let t1 = Thing(name: "Jack", age: 40)
let t2 = Thing(name: "Jill", age: 38)
let t3 = Thing(name: "Jill", age: 37)
let arr = [t1,t2,t3]
And of course I will prepare the empty dictionary, like your myDict, which I call d:
var d = [String : [Thing]]()
Now I will create the dictionary! The idea is to use map and filter together to do all the work of creating key-value pairs, and then we just build the dictionary from those pairs:
let pairs : [(String, [Thing])] = arr.map {
t in (t.name, arr.filter{$0.name == t.name})
}
for pair in pairs { d[pair.0] = pair.1 }