In Ruby or Rails, hash.merge({:order => 'asc'}) can return a new hash with a new key. What can return a new hash with a deleted key?

Question

In Ruby (or Rails), we can do

new_params = params.merge({:order => 'asc'})

and now new_params is a hash with an added key :order.

But is there a line there can return the hash with a deleted key? The line

new_params = params.delete(:order)

won't work because the delete method returns the value and that's it. Do we have to do it in 3 steps?

tmp_params = params
tmp_params.delete(:order)
return tmp_params

Is there a better way? Because I want to do a

new_params = (params[:order].blank? || params[:order] == 'desc') ? 
               params.merge({:order => 'asc') : 
               (foo = params; foo.delete(:order); foo)   # return foo

but the last line above is somewhat clumsy. Is there a better way to do it?

(note: because the default order is 'desc', so when there is no order param, that means it is the default and is desc, then toggle it to add order=asc, but otherwise, just remove the param order so that it is back to the default order of desc)

Answer 1

ActiveSupport adds a Hash#except method:

h1 = { a: 1, b: 2, c: 3 }
h1.except(:a) #=> {:b=>2, :c=>3}

A more complicated example:

h1 = { a:1, b: 2, c: 3 }
h2 = { b: 3, d: 5 }
h1.merge(h2).except(*h1.keys-h2.keys) #=> {:b=>3, :d=>5}

This will update keys that are present in h1 with the ones in h2, add the new ones from h2 and remove the ones that are in h1 but not in h2.

Answer 2

use reject:

{:hello=> 'aaa'}.reject {| key, value | key == :hello} #=> {}