Devise `find_first_by_auth_conditions` method explanation

问题

My two methods using Devise:

Method1

def self.find_first_by_auth_conditions(warden_conditions)
  conditions = warden_conditions.dup
  where(conditions).where(["lower(username) = :value OR lower(email)
    = :value", {:value => signin.downcase }]).first
end

Method2

def self.find_for_database_authentication(warden_conditions)
  conditions = warden_conditions.dup
  login = conditions.delete(:signin)
  where(conditions).where(["lower(username) = :value OR lower(email) = 
    :value", {:value => login.strip.downcase }]).first
end

My questions:

What does this code perform/do? login = conditions.delete(:signin)
Without the above code I get an error undefined local variable or method signin

回答1:

The following answers question 1)—specifically A) and B) below. The following code is an example and does not mirror the actual methods or arguments generated by Devise:

Here: the Hash contains :signin key-value pair and other valid ActiveRecord's #where syntax http://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-where

devise_conditions = {:signin => "cool@gmail.com", :deleted => false, :role => 'basic'} 
#=> {:signin=>"cool@gmail.com", :deleted => false, :role => 'basic'}

This duplicates original argument to prevent modification in order to use it in subsequent methods or queries http://ruby-doc.org/core-1.9.3/Object.html#method-i-dup

conditions = devise_conditions.dup 
#=> {:signin=>"cool@gmail.com", :deleted => false, :role => 'basic'}

Here, the code: A) deletes the :signin key-pair from the Hash; and B) assigns new variable signin with value of :signin key-pair from Hash http://www.ruby-doc.org/core-1.9.3/Hash.html#method-i-delete

signin = conditions.delete(:signin) 
#=> "cool@gmail.com"

The immediately above code could be rewritten to clarify both operations using additional "Element Reference" of Hash http://www.ruby-doc.org/core-1.9.3/Hash.html#method-i-5B-5D

signin = conditions[:signin]
#=> "cool@gmail.com"

conditions.delete(:signin)
#=> "cool@gmail.com" # deleted value from Hash is returned

conditions
#=> {:deleted => false, :role => 'basic'}

The method's original argument has been preserved by using dup

devise_conditions 
#=> {:signin=>"cool@gmail.com", :deleted => false, :role => 'basic'}

The following answers question 2):

Method1 does not create a variable signin. undefined local variable or method signin results from no signin variable being created when the code which creates it is removed.

Method2 creates a variable login which has the value from the original Hash named conditions with the key :signin.

回答2:

This deletes signin key from conditions hash and assigns its value to login local variable.

回答3:

2.. I guess you mean that signin is not defined in find_first_by_auth_conditions? Then I also guess that signin is an attribute of warden_conditions so you can try: warden_conditions.signin.

来源：https://stackoverflow.com/questions/23061116/devise-find-first-by-auth-conditions-method-explanation

标签

ruby-on-rails

ruby

activerecord

devise