Swift arrays are used to store ordered lists of values of the same
type. Swift 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 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.
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
You can create an empty array of a certain type using the following initializer syntax −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 −
import Cocoa 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])" )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 −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])" )When the above code is compiled and executed, it produces the following result −
Value of first element is 20 Value of second element is 30 Value of third element is 40You 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])" )When the above code is compiled and executed, it produces the following result −
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("Apple") someStrs.append("Amazon") someStrs += ["Google"] for item in someStrs { println(item) }When the above code is compiled and executed, it produces the following result −
Apple Amazon GoogleYou 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("Apple") someStrs.append("Amazon") someStrs += ["Google"] for (index, item) in enumerate(someStrs) { println("Value at index = \(index) is \(item)") }When the above code is compiled and executed, it produces the following result −
Value at index = 0 is Apple Value at index = 1 is Amazon Value at index = 2 is Google
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) }When the above code is compiled and executed, it produces the following 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)")When the above code is compiled and executed, it produces the following 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)")When the above code is compiled and executed, it produces the following result −
intsA.isEmpty = false intsB.isEmpty = false intsC.isEmpty = true
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