How to Delete an Entry of a Hash by Specifying its Key in Ruby?

Hashes is one of the most important data structures in Ruby. In this article, we will learn how to delete an entry of a hash by specifying its key in Ruby. We will discuss various approaches on how to delete an entry of a hash by specifying its key in Ruby.

Prerequisites

Before learning how to add key-value pairs to hashes in Ruby, we should have:

1. Install Ruby.
2. Basics of Ruby Programming.

What is Hash?

A hash is a collection of unique keys and their associated values pair.

1. In Ruby, hashes are created using curly braces {} with key-value pairs separated by commas.
2. They are similar to arrays, but they use keys as numerical indices to access elements.

Deleting an Entry from a Hash by Key

1. Using the delete Method

In this method we use delete method to delete a key-value pair from a hash. Here we pass the key we want to remove as an argument.

Syntax:

hash.delete(key)

• Example: In this example we use delete keyword to delete an entry New Delhi of the hash by specifying its key city in Ruby

person = { "name" => "Geeks", "age" => 20, "city" => "New Delhi" }
person.delete("city")

puts person

{"name"=>"Geeks", "age"=>20}

2. Using the delete_if Method

In this we use delete_if method to remove key-value pairs for which the block returns true.

Syntax:

hash.delete_if { |key, value| condition }

• Example: In this example we use delete_if keyword to delete an entry New Delhi of the hash by specifying its key city in Ruby

person = { "name" => "Geeks", "age" => 20, "city" => "New Delhi" }
person.delete_if { |key, _value| key == "age" }

puts person

{"name"=>"Geeks", "city"=>"New Delhi"}

3. Using the reject! Method

The reject! method is similar to delete_if, but it returns nil if no changes are made to the hash.

Syntax:

hash.reject! { |key, value| condition }

• Example: In this example we use reject! keyword to delete an entry New Delhi of the hash by specifying its key city in Ruby
  

person = { "name" => "Geeks", "age" => 20, "city" => "New Delhi" }
person.reject! { |key, _value| key == "city" }

puts person

{"name"=>"Geeks", "age"=>20}

Conditional Deletion

We can also delete key-value pairs from a hash based on specific conditions. For example, deleting entries where the value matches a condition.

Example: In this we delete key-value pairs from a hash based on specific conditions.

person = { "name" => "Geeks", "age" => 20, "city" => "New Delhi" }
person.delete_if { |key, value| value == 20 }

puts person

{"name"=>"Geeks", "city"=>"New Delhi"}

Conclusion

In Ruby, there are various ways to delete entries from a hash by specifying its key. The delete method is the most straightforward, but methods like delete_if and reject! provide additional flexibility when we need to delete based on conditions. Choosing the right method depends on your specific use case.