How to check if specific value is present in a hash?

Question

I'm using Rails and I have a hash object. I want to search the hash for a specific value. I don't know the keys associated with that value.

How do I check if a specific value is present in a hash? Also, how do I find the key associated with that specific value?

Answer 1

Hash includes Enumerable, so you can use the many methods on that module to traverse the hash. It also has this handy method:

hash.has_value?(value_you_seek) 

To find the key associated with that value:

hash.key(value_you_seek) 

This API documentation for Ruby (1.9.2) should be helpful.

Answer 2

The simplest way to check multiple values are present in a hash is:

h = { a: :b, c: :d } h.values_at(:a, :c).all? #=> true h.values_at(:a, :x).all? #=> false 

In case you need to check also on blank values in Rails with ActiveSupport:

h.values_at(:a, :c).all?(&:present?) 

or

h.values_at(:a, :c).none?(&:blank?) 

The same in Ruby without ActiveSupport could be done by passing a block:

h.values_at(:a, :c).all? { |i| i && !i.empty? }