Swift Array filter()

var numbers = [2, 3, 6, 9]

// return all the elements greater than 5 
var result = numbers.filter({ $0 > 5})

print(result)

// Output: [6, 9]

filter() Syntax

The syntax of the filter() method is:

array.filter(condition)

Here, array is an object of the Array class.

filter() Parameters

The filter() method takes one parameter:

1. condition - a closure that accepts a condition and returns a Bool value.

filter() Return Value

• returns all the elements from the array that satisfy the provided condition

Example 1: Swift Array filter()

var languages = ["Swedish", "Nepali", "Slovene", "Norwegian"]

// return all the elements that start with "N"
var result = languages.filter( { $0.hasPrefix("N") } )

print(result) 

Output

["Nepal", "Norwegian"]

In the above program, notice the closure definition,

{ $0.hasPrefix("N") }

This is a short-hand closure that checks whether all the elements in the array have the prefix "N" or not.

$0 is the shortcut to mean the first parameter passed into the closure.

The closure returns a Bool value depending upon the condition. If the condition is

• true - the array value is kept
• false - the array value is dropped/omitted

And finally, all the elements that start with "N" are stored in the result variable.

Example 2: Return Only Even Numbers From Array

var numbers = [2, 4, 5, 7, 8, 9]

// check if all elements are even numbers or not 
var result = numbers.filter({ $0 % 2 == 0 })

print(result)

Output

[2, 4, 8]