How to sort an array in descending order in Ruby

How to Sort an Array in Descending Order in Ruby 💎

Sorting an array in descending order can be a common challenge, especially when working with complex data structures such as arrays of hashes. In this guide, we will explore how to sort an array in descending order in Ruby and address common issues that arise during the process.

The Problem: Sorting an Array in Descending Order According to a Hash Value

Let's say we have an array of hashes like the following:

[
  { :foo => 'foo', :bar => 2 },
  { :foo => 'foo', :bar => 3 },
  { :foo => 'foo', :bar => 5 },
]

We want to sort this array in descending order based on the value of the :bar key in each hash. By default, Ruby's sort_by method sorts the array in ascending order. So how do we make it sort in descending order?

The Solution: Using a Custom Sort Algorithm with sort_by

To sort the array in descending order based on the :bar value, we can use a custom sort algorithm with the sort_by method. Here's how we can do it:

sorted_array = a.sort_by { |h| -h[:bar] }

By negating the h[:bar] value, we effectively reverse the sort order, resulting in a descending sort. However, using a negative sign might not seem appropriate, especially if you're striving for clean and readable code.

A Cleaner Solution: Using the Spaceship Operator `<=>

To make the code more intuitive, we can leverage the spaceship operator <=> in Ruby, which returns -1, 0, or 1 based on the comparison between two values. Here's how we can use it to sort our array in descending order:

sorted_array = a.sort_by { |h| -h[:bar] <=> 0 }

By comparing -h[:bar] with 0, we achieve the same result as before, but in a more straightforward and expressive manner.

Conclusion

Sorting an array in descending order can be accomplished by using a custom sort algorithm with sort_by and manipulating the comparison values. By leveraging either the negation or the spaceship operator, you can achieve a clean and readable solution to this common problem.

Now that you know how to sort an array in descending order in Ruby, go ahead and apply this knowledge to your own projects. Experiment with different sorting scenarios and explore the vast possibilities that Ruby offers.

If you found this guide helpful or have any further questions, please leave a comment below. Let's continue the conversation! 💬🚀