Extending/reopeining class and use of super

Rails
#1

A question on a couple things relating to extending a class and the use
of
super.

In my main application I have the following class which extends an
engine
class:

class User < ActiveRecord::Base
def self.find_for_database_authentication(login_value,
omniauth_provider=nil, omniauth_uid=nil)
super if login_value
where(‘omniauth_provider=? AND omniauth_uid=?’, omniauth_provider,
omniauth_uid)
end
end

And the engine has this class:

class User < ActiveRecord::Base
def self.find_for_database_authentication(login_value)
where([“username = :value OR email = :value”, { :value =>
login_value
}]).first
end
end

When I run a spec to try out the method, I get this error:
Failure/Error:
User.find_for_database_authentication(@user.username).class == User
NoMethodError:
super: no superclass method `find_for_database_authentication’
for
#Class:0x1057bbfa0

I do understand why – my application class is not a subclass of the
engine
class, I am just extending the class. This leaves me with the question
if
there is a way to have access to the original method (like using super
in a
subclass situation) so I would not have to duplicate that code (I would
have
subclassed my class to the engine class but is a bit nasty as they share
the
same name, and that is structurally how the app is loaded)?

Also, I am confused also as to why I see in places that to extend a
class
they use “MyClass.class_eval do …” whereas it seems that if I just
do
what I have above, I get the same ability. Am I missing something?

Anyhow, any comments appreciated!

David

#2

On 11 May 2011, at 18:17, David K. [email protected] wrote:

A question on a couple things relating to extending a class and the use of
super.

In my main application I have the following class which extends an engine class:

You are reopening the class (ie adding/changing methods in User), not
subclassing it, so super is looking for methods in activerecord::base.

Did you want to subclass User instead?

Fred

#3

On Wed, May 11, 2011 at 12:52 PM, Frederick C. <
[email protected]> wrote:

You are reopening the class (ie adding/changing methods in User), not
subclassing it, so super is looking for methods in activerecord::base.

Did you want to subclass User instead?

I tried but the thing is that the way the engine loads, the engine class
and
my class have the same name and reside in the local app. I guess I could
give my class a different name to subclass it if I dont want to dup the
code. Was just wondering if there was some other way but logically does
not
seem that there is.

#4

On May 11, 7:01pm, David K. [email protected] wrote:

class:
seem that there is.

You another way is to use alias_method_chain - you’d do something like

class Foo
class << self
def something_with_foo

end

alias_method_chain :something, :foo
end

end
end

What this does is rename the existing something method to
something_without_foo and renames your something_with_foo method to
something. Instead of calling super you call something_without_foo to
call the old something_method

Fred

#5

On Wed, May 11, 2011 at 3:29 PM, Frederick C. <
[email protected]> wrote:

super.
I tried but the thing is that the way the engine loads, the engine class
class Foo
What this does is rename the existing something method to
something_without_foo and renames your something_with_foo method to
something. Instead of calling super you call something_without_foo to
call the old something_method

Oh, that is interesting. I guess which would have be used carefully or
could
get confusing. This will be fun to play with. Thanks!