Swift Language Tutorial for Beginner 8 - Set

In Swift Language Tutorial for Beginner 7 - Dictionary, we understand the use of dictionary types in Swift, and now let’s take a look at collection types in Swift - Set.

Collections can be used to store unordered, non-duplicate data.

Declaration and initialization

var set1:Set<Int> = [1,2,3,4]
var set2 = Set(arrayLiteral: 1,2,3,4)

Note the differences with Array’s definition and initialization

Common operations

Determine the number of elements

Use the count property

set1.count

Determines whether the collection is empty

Use the isEmpty property

if set1.isEmpty {
    print("集合为空")
}

Determines whether an element is included

if set1.contains(1){
    print("集合包含")
}

Add an element

set1.insert(5)

Delete the element

set1.remove(1)

Note: The 1 here is not the ordinal number (subscript), it is the 1 element

Delete all elements

set1.removeAll()

Collection operations

Suppose there are two sets

var set3:Set<Int> = [1,2,3,4]
var set4:Set<Int> = [1,2,5,6]

Take the intersection

var setInter = set3.intersection(set4)

After the operation, setInter will contain {2, 1}

Take the union

var setUni = set3.union(set4)

After the operation, setUni will contain {4, 5, 6, 3, 1, 2}

Complement sets

var setEx = set3.symmetricDifference(set4)

After the operation, setEx will contain {4, 6, 3, 5}

Child collection judgment

Suppose there are several sets as follows:

var set5:Set = [1,2]
var set6:Set = [2,3]
var set7:Set = [1,2,3]
var set8:Set = [1,2,3]

1. Determining whether a subset of a set set5 is a subset of set7 returns ture

set5.isSubset(of: set7)

2. The superset set7 that determines whether it is a set of sets is the superset of set5 returns the ture

set7.isSuperset(of: set5)

3. Determines whether it is a true subset of a collection

set5 is a true subset of set7 returns to the form

set5.isStrictSubset(of: set7)

set7 is not a true superset of set8 returns false

set7.isStrictSuperset(of: set8)

Iterate over elements

You can use the for statement to traverse

for item in set7 {
    print(item)
}

You can also get the subscript of an element

for index in set7.indices {
    print(set7[index])
}

You can also set the sort to traverse

for item  in set7.sorted(by: >){
    print(item)
}

Next

Next, we’ll take a brief look at Function in Swift.