Swift - Arrays

Swift 4 arrays are used to store ordered psts of values of the same type. Swift 4 puts strict checking which does not allow you to enter a wrong type in an array, even by mistake.

If you assign a created array to a variable, then it is always mutable, which means you can change it by adding, removing, or changing its items; but if you assign an array to a constant, then that array is immutable, and its size and contents cannot be changed.

Creating Arrays

You can create an empty array of a certain type using the following initiapzer syntax −

var someArray = [SomeType]()

Here is the syntax to create an array of a given size a* and initiapze it with a value −

var someArray = [SomeType](count: NumbeOfElements, repeatedValue: InitialValue)

You can use the following statement to create an empty array of Int type having 3 elements and the initial value as zero −

var someInts = [Int](count: 3, repeatedValue: 0)

Following is one more example to create an array of three elements and assign three values to that array −

var someInts:[Int] = [10, 20, 30]

Accessing Arrays

You can retrieve a value from an array by using subscript syntax, passing the index of the value you want to retrieve within square brackets immediately after the name of the array as follows −

var someVar = someArray[index]

Here, the index starts from 0 which means the first element can be accessed using the index as 0, the second element can be accessed using the index as 1 and so on. The following example shows how to create, initiapze, and access arrays −

var someInts = [Int](count: 3, repeatedValue: 10)

var someVar = someInts[0]
print( "Value of first element is (someVar)" )
print( "Value of second element is (someInts[1])" )
print( "Value of third element is (someInts[2])" )

When the above code is compiled and executed, it produces the following result −

Value of first element is 10
Value of second element is 10
Value of third element is 10

Modifying Arrays

You can use append() method or addition assignment operator (+=) to add a new item at the end of an array. Take a look at the following example. Here, initially, we create an empty array and then add new elements into the same array −

var someInts = [Int]()

someInts.append(20)
someInts.append(30)
someInts += [40]

var someVar = someInts[0]

print( "Value of first element is (someVar)" )
print( "Value of second element is (someInts[1])" )
print( "Value of third element is (someInts[2])" )

Value of first element is 20
Value of second element is 30
Value of third element is 40

var someInts = [Int]()

someInts.append(20)
someInts.append(30)
someInts += [40]

// Modify last element
someInts[2] = 50

var someVar = someInts[0]

print( "Value of first element is (someVar)" )
print( "Value of second element is (someInts[1])" )
print( "Value of third element is (someInts[2])" )

Value of first element is 20
Value of second element is 30
Value of third element is 50

var someStrs = [String]()

someStrs.append("Apple")
someStrs.append("Amazon")
someStrs += ["Google"]
for item in someStrs {
   print(item)
}

Apple
Amazon
Google

var someStrs = [String]()

someStrs.append("Apple")
someStrs.append("Amazon")
someStrs += ["Google"]

for (index, item) in someStrs.enumerated() {
   print("Value at index = (index) is (item)")
}

Value at index = 0 is Apple
Value at index = 1 is Amazon
Value at index = 2 is Google

var intsA = [Int](count:2, repeatedValue: 2)
var intsB = [Int](count:3, repeatedValue: 1)

var intsC = intsA + intsB
for item in intsC {
   print(item)
}

2
2
1
1
1

var intsA = [Int](count:2, repeatedValue: 2)
var intsB = [Int](count:3, repeatedValue: 1)

var intsC = intsA + intsB

print("Total items in intsA = (intsA.count)")
print("Total items in intsB = (intsB.count)")
print("Total items in intsC = (intsC.count)")

Total items in intsA = 2
Total items in intsB = 3
Total items in intsC = 5

var intsA = [Int](count:2, repeatedValue: 2)
var intsB = [Int](count:3, repeatedValue: 1)
var intsC = [Int]()

print("intsA.isEmpty = (intsA.isEmpty)")
print("intsB.isEmpty = (intsB.isEmpty)")
print("intsC.isEmpty = (intsC.isEmpty)")

intsA.isEmpty = false
intsB.isEmpty = false
intsC.isEmpty = true