How to return first 5 objects of Array in Swift?

Question

By far the neatest way to get the first N elements of a Swift array is using prefix(_ maxLength: Int):

let someArray = [1, 2, 3, 4, 5, 6, 7]
let first5 = someArray.prefix(5) // 1, 2, 3, 4, 5

This has the benefit of being bounds safe. If the count you pass to prefix is larger than the array count then it just returns the whole array.

NOTE: as pointed out in the comments, Array.prefix actually returns an ArraySlice, not an Array. In most cases this shouldn't make a difference but if you need to assign the result to an Array type or pass it to a method that's expecting an Array param you will need to force the result into an Array type: let first5 = Array(someArray.prefix(5))

Update: There is now the possibility to use prefix to get the first n elements of an array. Check @mluisbrown's answer for an explanation how to use prefix.

Original Answer: You can do it really easy without filter, map or reduce by just returning a range of your array:

var wholeArray = [1, 2, 3, 4, 5, 6]
var n = 5

var firstFive = wholeArray[0..<n] // 1,2,3,4,5

With Swift 5, according to your needs, you may choose one of the 6 following Playground codes in order to solve your problem.

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#1. Using subscript(_:) subscript

let array = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L"]
let arraySlice = array[..<5]
//let arraySlice = array[0..<5] // also works
//let arraySlice = array[0...4] // also works
//let arraySlice = array[...4] // also works
let newArray = Array(arraySlice)
print(newArray) // prints: ["A", "B", "C", "D", "E"]

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#2. Using prefix(_:) method

Complexity: O(1) if the collection conforms to RandomAccessCollection; otherwise, O(k), where k is the number of elements to select from the beginning of the collection.

let array = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L"]
let arraySlice = array.prefix(5)
let newArray = Array(arraySlice)
print(newArray) // prints: ["A", "B", "C", "D", "E"]

Apple states for prefix(_:):

If the maximum length exceeds the number of elements in the collection, the result contains all the elements in the collection.

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#3. Using prefix(upTo:) method

Complexity: O(1)

let array = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L"]
let arraySlice = array.prefix(upTo: 5)
let newArray = Array(arraySlice)
print(newArray) // prints: ["A", "B", "C", "D", "E"]

Apple states for prefix(upTo:):

Using the prefix(upTo:) method is equivalent to using a partial half-open range as the collection's subscript. The subscript notation is preferred over prefix(upTo:).

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#4. Using prefix(through:) method

let array = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L"]
let arraySlice = array.prefix(through: 4)
let newArray = Array(arraySlice)
print(newArray) // prints: ["A", "B", "C", "D", "E"]

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#5. Using removeSubrange(_:) method

Complexity: O(n), where n is the length of the collection.

var array = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L"]
array.removeSubrange(5...)
print(array) // prints: ["A", "B", "C", "D", "E"]

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#6. Using dropLast(_:) method

Complexity: O(1) if the collection conforms to RandomAccessCollection; otherwise, O(k), where k is the number of elements to drop.

let array = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L"]
let distance = array.distance(from: 5, to: array.endIndex)
let arraySlice = array.dropLast(distance)
let newArray = Array(arraySlice)
print(newArray) // prints: ["A", "B", "C", "D", "E"]

let a: [Int] = [0, 0, 1, 1, 2, 2, 3, 3, 4]
let b: [Int] = Array(a.prefix(5))
// result is [0, 0, 1, 1, 2]