Swift learning: Swift programming tour-Sets of Collection types (7) and swiftsets

Swift learning: Swift programming tour-Sets of Collection types (7) and swiftsets

Sets are unordered values of the same type. You can use Sets to replace arrays when order is not important, or if you need to appear the same value only once in the set.

I. Sets type syntax

WritingSet <Element>,ElementIs the type of sets that can be stored

　　Create and initialize an empty set

var letters = Set<Character>()print("letters is of type Set<Character> with \(letters.count) items.")// Prints "letters is of type Set<Character> with 0 items.

 

 

If you can infer the type of its elements, you can also write

letters = []

 

 

Use the array literal to create a set

var favoriteGenres: Set<String> = ["Rock", "Classical", "Hip hop"]// favoriteGenres has been initialized with three initial items

Or (because it can be inferred as set <String>)

var favoriteGenres:Set = ["Rock", "Classical", "Hip hop"]// favoriteGenres has been initialized with three initial items

 

 

Access and modify

The count method returns the number of set data items.

print("I have \(favoriteGenres.count) favorite music genres.")// Prints "I have 3 favorite music genres.

 

 

IsEmpty checks whether set is empty

 

Contains (_ :) check whether the set object contains specific data.

if favoriteGenres.contains("Funk") {    print("I get up on the good foot.")} else {    print("It's too funky in here.")}// Prints "It's too funky in here.

 

　　

Add new data item

Insert (_ :) Add new data to an existing set object

favoriteGenres.insert("Jazz")// favoriteGenres now contains 4 items

 

 

Delete existing data items

Remove (_ :) delete existing data from an existing set object

if let removedGenre = favoriteGenres.remove("Rock") {    print("\(removedGenre)? I'm over it.")} else {    print("I never much cared for that.")}// Prints "Rock? I'm over it.

 

 

Traverse set

Use the forin statement to traverse the set

for genre in favoriteGenres {    print("\(genre)")}// Classical// Jazz// Hip hop

 

 

Set unordered data storage. You can use sort () to sort data in ascending order.

 

Intersect (_ :) creates a new set object that contains data shared by two Set objects.

ExclusiveOr (_ :) is a new set object that does not contain data shared by two Set objects.

Union (_ :) creates a new set object that contains all the data of two Set objects.

Subtract (_ :) creates a new set object that only contains one of the existing Set data.

let oddDigits: Set = [1, 3, 5, 7, 9]let evenDigits: Set = [0, 2, 4, 6, 8]let singleDigitPrimeNumbers: Set = [2, 3, 5, 7] oddDigits.union(evenDigits).sort()// [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]oddDigits.intersect(evenDigits).sort()// []oddDigits.subtract(singleDigitPrimeNumbers).sort()// [1, 9]oddDigits.exclusiveOr(singleDigitPrimeNumbers).sort()// [1, 2, 9]

 

 

 

 

= The operator compares whether the values of the two sets are all the same

let houseAnimals: Set = ["