How to "intercept" each action call?

rubyonrails-talk
1

Hi!

I’m a RoR beginner and I’m trying to make a gem that can “intercepts” all action from my controllers.

I would like to do something like that:

class ApplicationController < ActionController::Base

include MyGem

end

class MyController < ApplicationController

do_something_to :some_attribute

def index

respond_with(@some_attribute)

end

end

In each call of index or other action from MyController, I want that MyGem execute “do_something_to” modifying the value of “some_attribute”. Is it possible?

Thanks,

Lauro Caetano

2

You need a before_filter.

http://edgeguides.rubyonrails.org/action_controller_overview.html#filters

Dheeraj Kumar

3

You need a before_filter.

http://edgeguides.rubyonrails.org/action_controller_overview.html#filters

Dheeraj Kumar

4

You need a before_filter.

http://edgeguides.rubyonrails.org/action_controller_overview.html#filters

Dheeraj Kumar

5

Thanks for your help Dheeraj, but I’m trying to do something like Responders.

Responders has a respond_to :html in controllers, that is used in each action call to respond_with.

The thing is: call a specific method that is located inside my gem for every action call. This method should be able to modify the attribute that was passed.

I have no idea to make this work.

6

Thanks for your help Dheeraj, but I’m trying to do something like Responders.

Responders has a respond_to :html in controllers, that is used in each action call to respond_with.

The thing is: call a specific method that is located inside my gem for every action call. This method should be able to modify the attribute that was passed.

I have no idea to make this work.

Can you give an example of this working, please? I don’t understand what you mean by “the attribute that was passed”. What modifications is it going to make?

7

I don’t understand your exact request, but let’s see if this helps you.

You can run filters before every action call. Inside the filter method/class, you can call your gem’s methods. Also, they can modify the params hash.

See this for two examples, one showing a filter method, and another a filter class.

http://stackoverflow.com/questions/2913113/access-params-and-local-attributes-in-static-class-as-filter

Dheeraj Kumar

8

I’m trying to do this:

class ApplicationController < ActionController::Base

include MyGem

end

class TasksController < ApplicationController

injector_to :task

def show

respond_with(@task)

end

end

When the action ‘show’ is called, the “injector_to” should inject the @task for me.

In other words, injector_to makes “Task.find(params[id])” for me in this case.

Other example: If I have this action →

def create

respond_with(@task)

end

the injector_to should do the hard work, instantiating the @task and saving it.

I think that I’ve explained better now.

9

I’m trying to do this:

class ApplicationController < ActionController::Base

include MyGem

end

class TasksController < ApplicationController

injector_to :task

def show

respond_with(@task)

end

end

OK, so you’re trying to automate the default behaviour for a standard controller without using scaffolding? That makes sense.

Two methods spring to mind.

  1. A generic controller than handles the methods that other controllers inherit from. You then set the variable name and class in each child controller, maybe via overloaded methods or through your injector_to method.

  2. Your gem adds injector_to to ActiveController. When called it dynamically adds the standard methods to the controller. You then patch ActiveController so rather than looking for the “show” method, it looks for “injected_show”, etc, which calls the scaffold code, then calls the controller-specific “show” method if there is one. That’s the nicest way of doing it from an end-user point of view.

I actually quite like this idea. If you want some help writing them Gem, let me know offlist and I’ll happily help.

10

I understand. See the link I posted, where the OP does exactly your requirement. Here’s some code:

class ApplicationController < ActionController::Base

include MyGem

end

class TasksController < ApplicationController

before_filter :find_task

def find_task

@task = Task.find(params[:id])

Some other operation involving MyGem if you need…

end

def show

respond_with(@task)

end

end

Dheeraj Kumar

11

@Jeremy:

#1 seems to be the easiest, but #2 is the best solution.

Here’s my view of how this can work:

class TasksController < ApplicationController

Specify which class has the generic scaffolding methods

scaffold :my_custom_scaffold_class

or we bundle a generic class with the gem

scaffold

Overriding is possible

def show(id)

instance variable is already injected by our gem

do something with the @task

end

end

or even

class ApplicationController < ActionController::Base

scaffold

end

to propagate to all controllers which inherit from ApplicationController.

Dheeraj Kumar

12

Thank very much for all your help =)

@Jeremy the #2 is awesome :slight_smile:

@Dheeraj your point of view is really coll too!

And yes! I would like to get some help to get this gem done.

I’ve created a github repo at: https://github.com/laurocaetano/injector

At time, sorry for my really bad english =(

Thanks guys!