Today I Learned

A Hashrocket project

Rails' `Hash#except`

A cool feature provided by Rails is the #except method on Hash. This function removes a key-value pair from a hash.

Let’s remove a Rails parameter, the most obvious use case I can think of:

[1] pry(#<SessionsController>)> params
=> {"utf8"=>"✓",
 "user_login"=>{"email"=>"", "password"=>"general"},
 "controller"=>"sessions",
 "action"=>"create"}
[2] pry(#<SessionsController>)> params.except(:utf8)
=> {"user_login"=>{"email"=>"", "password"=>"general"},
 "controller"=>"sessions",
 "action"=>"create"}

And the source code:

[1] pry(#<SessionsController>)> show-source Hash#except
From: /Users/dev/.rvm/gems/ruby-2.2.5/gems/activesupport-4.2.7.1/lib/active_support/core_ext/hash/except.rb @ line 9:
Owner: Hash
Visibility: public
Number of lines: 3

def except(*keys)
  dup.except!(*keys)
end
[2] pry(#<SessionsController>)> show-source Hash#except!

From: /Users/dev/.rvm/gems/ruby-2.2.5/gems/activesupport-4.2.7.1/lib/active_support/core_ext/hash/except.rb @ line 17:
Owner: Hash
Visibility: public
Number of lines: 4

def except!(*keys)
  keys.each { |key| delete(key) }
  self
end

Thanks Rails!

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