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What is set.prefix() 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

The prefix() method is used on a set, and it returns a sub-sequence up to the specified length with the initial elements of the particular set.

Syntax

set.prefix(length)
Syntax for prefix() method of a Set in Swift

Parameters

The prefix() method takes length as a parameter that represents the number of elements of a sub-sequence, we want to return.

Return value

This method returns a sub-sequence.

Code example

Let's look at the code below:

// create some sets
let names: Set = ["Alicia", "Bethany", "Chris", "Diana", "Eric"]
let numbers: Set = [1, 2, 3, 4, 5, 7, 8, 9, 10]
// get some sub-sequence using the prefix() method
var prefix1 = names.prefix(2)
var prefix2 = numbers.prefix(5)
// print each element
for each in prefix1{
print(each)
}
// print each element
for each in prefix2{
print(each)
}
Using the prefix() method

Explanation

  • Lines 2 and 3: We create a couple of sets.
  • Lines 6 and 7: We get a particular sub-sequence of a set using the prefix() method. Then, we store this sub-sequence in variables prefix1 and prefix2.
  • Line 10 to 15: We use the for-in loop to print each element of the sub-sequences.

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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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