Ruby: Easiest Way to Filter Hash Keys?

Question

I have a hash that looks something like this:

params = { :irrelevant => \"A String\",
           :choice1 => \"Oh look, another one\",
           :choi         


        

Answer 1

This is a one line to solve the complete original question:

params.select { |k,_| k[/choice/]}.values.join('\t')

But most the solutions above are solving a case where you need to know the keys ahead of time, using slice or simple regexp.

Here is another approach that works for simple and more complex use cases, that is swappable at runtime

data = {}
matcher = ->(key,value) { COMPLEX LOGIC HERE }
data.select(&matcher)

Now not only this allows for more complex logic on matching the keys or the values, but it is also easier to test, and you can swap the matching logic at runtime.

Ex to solve the original issue:

def some_method(hash, matcher) 
  hash.select(&matcher).values.join('\t')
end

params = { :irrelevant => "A String",
           :choice1 => "Oh look, another one",
           :choice2 => "Even more strings",
           :choice3 => "But wait",
           :irrelevant2 => "The last string" }

some_method(params, ->(k,_) { k[/choice/]}) # => "Oh look, another one\\tEven more strings\\tBut wait"
some_method(params, ->(_,v) { v[/string/]}) # => "Even more strings\\tThe last string"