Determine if hash contains any key from a set of keys?

Question

Do you know a pretty ruby way to find if an hash has one of some keys ?

h = {:a => 1, :c => 3, :d => 4}
# keys to find are :a, :b or :e

I know that I can do a :

h.key?(:a) || h.key?(:b) || h.key?(:e)

But I was wondering if there was a prettier way to do it ! :)

Thanks a lot !

Solution 1

Here is how you get all of the matching keys from an array:

> {:a => 1, :c => 3, :d => 4}.keys & [:a, :d, :e]
 => [:a, :d] 

and if you want a boolean (following Andrew's suggestion):

> ({:a => 1, :c => 3, :d => 4}.keys & [:a, :d, :e]).empty?
 => false 
> ({:a => 1, :c => 3, :d => 4}.keys & [:f, :e]).empty?
 => true 

Solution 2

I would do something like this:

[:a, :b, :e].any?{ |val| h.key?(val) } 

Solution 3

h.select{|k| [:b, :w, :e].include?(k) }.empty?
h.select{|k| [:a, :w, :e].include?(k) }.empty?

And you get hash (key and value) of matching key in return (without empty?)

Comments

[Pratik Khadloya]

Checkout this awesome answer which does not use any loops: stackoverflow.com/a/4743729/238880

[Admin]

+1 Nice "alternative" solution with a set intersection. I would add that length > 0 of the result implied existence of at least one key.

[oligan]

@pst: You could use .empty? if you just wanted a boolean.

[famousgarkin]

Or .any? to check the opposite.

[poorva]

.keys converts symbolic keys into strings, so it should be check like - {:a => 1, :c => 3, :d => 4}.keys & ['a', 'd', 'e'].