"first" helper method

I've been looking at a project for a login module, but I'm not sure exactly what this helper method is doing:

def self.authenticate(login, pass)
  u = User.first(:login => login)
  return 开发者_JS百科nil if u.nil?
  return u if User.encrypt(pass, u.salt) == u.hashed_password
  nil
end

Why not instead of:

u = User.first(:login => login)

...you do something like:

u = self.login

Thanks!

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The first helper method locates the first record in your database that matches the specified criteria. It's semantically equivalent to the following SQL statement:

SELECT * FROM Users WHERE login = 'foo' LIMIT 1

The code after u = User.first(:login => login) does the following: 1. Checks to see if there is a user returned with the specified login 2. Returns the User object if the passwords match.

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u = User.first(:login => login)

means "go to the database, and find me the first User object whose login equals the userid passed in as the "login" parameter. Assign this to u.

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Because you're looking for the corresponding user object, not just the login name.