Sort_by for custom sorting in Ruby

Introduction

Sorting helps organize data in a way that makes it easier to find or understand. sort_by lets you decide exactly how to sort things based on your own rules.

When you want to sort a list of names by their length instead of alphabetically.

When you have a list of people and want to sort them by their age.

When sorting a list of files by their size or date created.

When you want to sort objects by a specific property, like price or rating.

Syntax

Ruby

array.sort_by { |item| expression }

The block inside { } tells Ruby what to use for sorting each item.

The original array is not changed; sort_by returns a new sorted array.

Examples

This sorts names by their length, shortest first.

Ruby

names = ["Bob", "Alice", "Eve"]
sorted = names.sort_by { |name| name.length }

This sorts numbers in descending order by using the negative value.

Ruby

numbers = [5, 2, 9, 1]
sorted = numbers.sort_by { |num| -num }

This sorts people by their age, youngest first.

Ruby

people = [{name: "Bob", age: 30}, {name: "Alice", age: 25}]
sorted = people.sort_by { |person| person[:age] }

Sample Program

This program sorts a list of fruits by the length of their names and prints the sorted list.

Ruby

fruits = ["apple", "banana", "pear", "kiwi"]
sorted_fruits = fruits.sort_by { |fruit| fruit.length }
puts sorted_fruits

Important Notes

If two items have the same sorting value, their order stays the same as in the original list (stable sort).

Use sort_by when sorting by a single property or calculation for better speed than sort with a block.

Summary

sort_by sorts items based on a value you choose for each item.

It returns a new sorted array without changing the original.

Use it to sort by length, age, price, or any custom rule you want.