I have an array (array1) of hashes that looks like this :
array1 = [ {:ID=>"1", :value=>"abc"}, {:ID=>"2", :value=>"def"} ] I can loop over each hash and check each hash value manually:
array1.each do |h| if h.has_value?("def") #do something end end Is there a way to check if the hash value "abc" exists within a hash inside the array without having to iterate over the array?
find method is the most concise way with an array.
array1.find { |item| item[:value] == 'abc' } Anyway, if you can start directly with an hash is better but if you have to switch to an hash from an array to have the O(1) lookup, it will probably be slower anyway.
use any? instead of each, it breaks in early stage if found, best case O(1) and worst case O(n)
word = "def" is_present = array1.any? { |h| h.has_value?(word) } is_present is true if word is found in hash otherwise false
O(n).
any? will stop processing at the first true value, avoiding a full array scan.One way or another, you can't avoid iterating over the array. Here's one way.
array1.flat_map(&:values).include?("def") #=> true Note
array1.flat_map(&:values) #=> ["1", "abc", "2", "def"] 
"1" and "2" should be here.You obviously have to iterate at least once over the elements of your array.
If you do this often, you should use another data format:
array1 = [ { ID: '1', value: 'abc' }, { ID: '2', value: 'def' }, { ID: '3', value: 'abc' } ] lookup_table = array1.each_with_object(Hash.new { |h, k| h[k] = [] }) do |hash, table| table[hash[:value]] << hash[:ID] end p lookup_table # {"abc"=>["1", "3"], "def"=>["2"]} p lookup_table['abc'] # ["1", "3"] As a bonus, it gives you all the IDs for which this value is found, and it gives it fast.
If you just want to know if there's a value somewhere in your hashes, you could use a Set:
require 'set' all_values = Set.new(array1.map{|h| h[:value]}) p all_values.include? 'abc' # true p all_values.include? 'xyz' # false Again, the lookup will be much faster than with an array of hashes.
O(1)point of lookup for hash tables. Just use a JS Object literal for this.array1come from, how is it generated? Is it possible to change the structure (for example to an hash) at the origin ofarray1?"1"to be a value inside a hash of your array?