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What is the prefix(upTo:) array method in Swift?

Theodore Kelechukwu Onyejiaku

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

Overview

prefix(upTo:) is an array method that is used to return a new array of elements. The new array contains elements of the original array up to, but not including, the specified position.

Syntax

arr.prefix(upTo: position)

Parameters

position: This is the position up to which the returned array returns the elements of arr. The returned elements do not include the element in this position.

Return value

This method returns an array up to, but not including, the specified position.

Code example

// create arrays
let numbers = [2, 1, 45, 3, 9]
let fruits = ["orange", "apple", "banana", "water-melon", "grape"]
let gnaam = ["Google", "Netflix", "Amazon", "Apple", "Meta"]
// get some elements
// and print results
print(numbers.prefix(upTo: 2)) // [2,1]
print(fruits.prefix(upTo: 1)) // ["orange"]
print(gnaam.prefix(upTo: 5)) // ["Google", "Netflix", "Amazon", "Apple", "Meta"]
Getting some array elements up to a certain position in Swift

Explanation

  • Lines 2-4: We create some arrays.
  • Lines 8-10: We invoke the prefix(upTo:) method on the arrays and print the results to the console.

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communitycreator

CONTRIBUTOR

Theodore Kelechukwu Onyejiaku

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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