Question

I am trying to figure out how I can filter out key and value pairs from one filter into another

For example I want to take this hash

x = { 'one' => 'one', 'two' => 'two', 'three' => 'three'}  y = x.some_function  y == { 'one' => 'one', 'two' => 'two'} 

Thanks for your help

EDIT: should probably mention that in this example, I want it to behave as a whitelist filter. That is, I know what I want, not what I don’t want.

Answer 1

Maybe this it what you want.

wanted_keys = %w[one two] x = { 'one' => 'one', 'two' => 'two', 'three' => 'three'} x.select { |key,_| wanted_keys.include? key } 

The Enumerable mixin which is included in e.g. Array and Hash provides a lot of useful methods like select/reject/each/etc.. I suggest that you take a look at the documentation for it with ri Enumerable.