Create hash using block (Ruby)

In Ruby 1.9 (or with ActiveSupport loaded, e.g. in Rails), you can use Object#tap, e.g.:

foo = Hash.new.tap do |bar|  bar[:baz] = 'qux'end

You can pass a block to Hash.new, but that serves to define default values:

foo = Hash.new { |hsh, key| hsh[key] = 'baz qux' }foo[:bar]   #=> 'baz qux'

For what it's worth, I am assuming that you have a larger purpose in mind with this block stuff. The syntax { :foo => 'bar', :baz => 'qux' } may be all you really need.

I cannot understand why

foo = {  :apple => "red",  :orange => "orange",  :grape => "purple"}

is not working for you?

I wanted to post this as comment but i couldn't find the button, sorry

Passing a block to Hash.new specifies what happens when you ask for a non-existent key.

foo = Hash.new do |f|  f[:apple] = "red"  f[:orange] = "orange"  f[:grape] = "purple"endfoo.inspect # => {}foo[:nosuchvalue] # => "purple"foo # => {:apple=>"red", :orange=>"orange", :grape=>"purple"}

As looking up a non-existent key will over-write any existing data for :apple, :orange and :grape, you don't want this to happen.

Here's the link to the Hash.new specification.