Swift arrays are used to store
ordered lists of values of the same data type. If you assign a created array to a
variable then its 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
Example of Empty Array
var
someArray = [SomeType]()
Here is the syntax to create an
array of a given size a* and initialize 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, initialize, and access arrays −
var someInts = [Int](count: 3, repeatedValue: 10)
var someVar = someInts[0]
println( "Value of first element is \(someVar)" )
println( "Value of second element is \(someInts[1])" )
println( "Value of third element is \(someInts[2])" )
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 −
import Cocoa
var someInts = [Int]()
someInts.append(20)
someInts.append(30)
someInts += [40]
var someVar = someInts[0]
println( "Value of first element is \(someVar)" )
println( "Value of second element is \(someInts[1])" )
println( "Value of third element is \(someInts[2])" )
Result:
Value
of first element is 20
Value
of second element is 30
Value
of third element is 40
You can modify an existing element
of an Array by assigning a new value at a given index as shown in the following
example −
import Cocoa
var someInts = [Int]()
someInts.append(20)
someInts.append(30)
someInts += [40]
// Modify last element
someInts[2] = 50
var someVar = someInts[0]
println( "Value of first element is \(someVar)" )
println( "Value of second element is \(someInts[1])" )
println( "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
Iterating Over an Array
You can use for-in loop to
iterate over the entire set of values in an array as shown in the following
example −
import Cocoa
var someStrs = [String]()
someStrs.append("A")
someStrs.append("B")
someStrs += ["C"]
for item in someStrs {
println(item)
}
Result:
A
B
C
You can use enumerate()
function which returns the index of an item along with its value as shown below
in the following example −
import Cocoa
var someStrs = [String]()
someStrs.append("A")
someStrs.append("B")
someStrs += ["C"]
for (index, item) in enumerate(someStrs) {
println("Value
at index = \(index) is \(item)")
}
Result:
Value
at index = 0 is A
Value
at index = 1 is B
Value
at index = 2 is C
Adding Two Arrays
You can use the addition operator
(+) to add two arrays of the same type which will yield a new array with a
combination of values from the two arrays as follows −
import Cocoa
var intsA = [Int](count:2, repeatedValue: 2)
var intsB = [Int](count:3, repeatedValue: 1)
var intsC = intsA + intsB
for item in intsC {
println(item)
}
Result:
2
2
1
1
1
The count Property
You can use the read-only count
property of an array to find out the number of items in an array shown below −
import Cocoa
var intsA = [Int](count:2, repeatedValue: 2)
var intsB = [Int](count:3, repeatedValue: 1)
var intsC = intsA + intsB
println("Total items in intsA = \(intsA.count)")
println("Total items in intsB = \(intsB.count)")
println("Total items in intsC = \(intsC.count)")
Result:
Total
items in intsA = 2
Total
items in intsB = 3
Total
items in intsC = 5
The empty Property
You can use the read-only empty
property of an array to find out whether an array is empty or not as shown
below −
import Cocoa
var intsA = [Int](count:2, repeatedValue: 2)
var intsB = [Int](count:3, repeatedValue: 1)
var intsC = [Int]()
println("intsA.isEmpty = \(intsA.isEmpty)")
println("intsB.isEmpty = \(intsB.isEmpty)")
println("intsC.isEmpty = \(intsC.isEmpty)")
Result:
intsA.isEmpty
= false
intsB.isEmpty
= false
intsC.isEmpty
= true
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