Swift Array prefix()

var numbers = [2, 4, 6, 8, 10, 11, 12, 13]

// return first 5 elements 
print(numbers.prefix(5))

// Output: [ 2, 4, 6, 8, 10 ]

prefix() Syntax

The syntax of the array prefix() method is:

array.prefix(number: Int)

Here, array is an object of the Array class.

prefix() Parameters

The prefix() method takes a single parameter:

• number - number of elements to return from array

Note: number must be greater than or equal to 0.

prefix() Return Value

• returns the specified number of elements from the starting element.

Example 1: Swift Array prefix()

var languages = ["Swift", "C", "Java", "Objective-C", "Kotlin"]

// return first 3 elements 
print(languages.prefix(3))

var prime = [9, 12, 52, 43]

// return first 2 elements 
print(prime.prefix(2))

Output

["Swift", "C", "Java"]
[9, 12]

In the above example,

• languages.prefix(3) returns the first 3 elements of the languages array
• prime.prefix(2) returns the first 2 elements of the prime array.

Example 2: Return Empty And Original Array using prefix()

var names = ["Greg", "Ludovico", "Ben", "Cartman"]

// return empty array 
print(names.prefix(0))

// return original array 
print(names.prefix(4))

Output

[]
["Greg", "Ludovico", "Ben", "Cartman"]

Here,

• names.prefix(0) - since we have passed 0, the method returns an empty array.
• names.prefix(4) - since the number of elements to return (4) is equal to the number of elements in the array, the method returns the original array.

Note: Even if the number of elements to return is greater than the number of elements in the array, the method returns the original array.