Question

I have a Ruby hash:

@tags = { "project_status" => { "title" => "Project status" }, 
          "milestones"     => { "title" => "Milestones"},
          "lessons"        => { "title" => "Lessons"}, 
          "tasks"          => { "title" => "Tasks"} }

I’d like to shift specific key-value pairs out of this hash.
e.g. if I am interested in "milestones" tags, then shift on the hash will give me:

=> ["milestones", {"title"=>"Milestones"}] 

Which is exactly what I want.

Except that I can’t work out how to select a specific key-value pair.

I could write something to iterate through the hash until I find the matching key and then call shift, but I’m assuming there’s a cleaner “Ruby way” to do this 🙂

Answer 1

delete is probably what you’re looking for. It removes corresponding key from the hash (whereas shift removes item from an array)

tags = { "project_status" => { "title" => "Project status" }, 
          "milestones"     => { "title" => "Milestones"},
          "lessons"        => { "title" => "Lessons"}, 
          "tasks"          => { "title" => "Tasks"} }

def shift hash, key
  [key, hash.delete(key)] # removes key/value pair
  # [key, hash[key]] # leaves key/value pair
end          

shift tags, 'milestones' # => ["milestones", {"title"=>"Milestones"}]
tags # => {"project_status"=>{"title"=>"Project status"}, "lessons"=>{"title"=>"Lessons"}, "tasks"=>{"title"=>"Tasks"}}