How To Get Key From Hash In Ruby

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In this blog post, we will discuss how to get a key from a given hash in Ruby by using different methods. In Ruby, a hash is a collection of key-value pairs, where each key is associated with a single value. We can use the key to access its corresponding value in the hash.

Finding a Key Using the key() Method

Ruby provides a built-in method called key() that can be used to find the key for a specific value in a hash. The key() method returns the first key that has the given value or nil if no such key is found.

Here’s an example:

my_hash = {"apple" => "fruit", "carrot" => "vegetable", "salmon" => "fish"}

key = my_hash.key("vegetable")
puts key
# Output: "carrot"



Finding a Key Using the select() Method


Another way to get a key from a hash is by using the select() method. The select() method returns a new hash containing all the key-value pairs for which the given block returns true.


Here’s an example of how to use select() to get a key from a hash:


my_hash = {"apple" => "fruit", "carrot" => "vegetable", "salmon" => "fish"}

selected_key_value = my_hash.select { |_key, value| value == "fish" }
puts selected_key_value.keys
# Output: ["salmon"]



Finding a Key Using the find() Method


Ruby also provides a find() method that can be used to get a key from a hash. The find() method returns the first key-value pair for which the given block returns true.


Here’s an example of how to use find() to get a key from a hash:


my_hash = {"apple" => "fruit", "carrot" => "vegetable", "salmon" => "fish"}

key_value = my_hash.find { |_key, value| value == "fruit" }
puts key_value[0]
# Output: "apple"



Conclusion


In this blog post, we have discussed different methods to get a key from a hash in Ruby, including the key(), select(), and find() methods. Each method serves a different purpose and can be used based on the specific requirements of your application.