before_filter with parameters

Question

I have a method that does something like this:

before_filter :authenticate_rights, :only => [:show]

def authenticate_rights
  project = Project.find(params[:id])
  redirect_to signin_path unless project.hidden
end

I also want to use this method in some other Controllers, so i copied the method to a helper that is included in the application_controller.

the problem is, that in some controllers, the id for the project isn't the :id symbol but f.e. :project_id (and also a :id is present (for another model)

How would you solve this problem? is there an option to add a parameter to the before_filter action (to pass the right param)?

Solution 1

I'd do it like this:

before_filter { |c| c.authenticate_rights correct_id_here }

def authenticate_rights(project_id)
  project = Project.find(project_id)
  redirect_to signin_path unless project.hidden
end

Where correct_id_here is the relevant id to access a Project.

Solution 2

With some syntactic sugar:

before_filter -> { find_campaign params[:id] }, only: [:show, :edit, :update, :destroy]

Or if you decide to get even more fancy:

before_filter ->(param=params[:id]) { find_campaign param }, only: %i|show edit update destroy|

And since Rails 4 before_action, a synonym to before_filter, was introduced, so it can be written as:

before_action ->(param=params[:id]) { find_campaign param }, only: %i|show edit update destroy|

NB

-> stands for lambda, called lambda literal, introduce in Ruby 1.9

%i will create an array of symbols

Solution 3

To continue @alex' answer, if you want to :except or :only some methods, here is the syntax:

before_filter :only => [:edit, :update, :destroy] do |c| c.authenticate_rights params[:id] end 

Found here.

Solution 4

I find the block method using curly braces instead of do...end to be the clearest option

before_action(only: [:show]) { authenticate_rights(id) }

before_action is just the newer preferred syntax for before_filter

View more solutions

Comments

[choise]

the problem is, sometimes both are present (nested) and it finds a project that isn't the right one.

[choise]

is there a way to add a ,:only => [:show] symbol? i'm getting an error trying before_filter { |c| c.authenticate_rights correct_id_here }, :only => [:show]

[fguillen]

Try the other way around: before_filter(:only => [:show]) { <block_code_here> }. More examples here: apidock.com/rails/ActionController/Filters/ClassMethods/…

[Richard Michael]

If you secure this by making the before_filter a private method, then perhaps re-factor (e.g. move it to a parent controller, ApplicationController, etc.), you'll need to use c.send(:filter_name, ...) as the filter will not run in the controller context. guides.rubyonrails.org/…

[oreoshake]

Doing this makes it so the before_filter cannot be overridden/skipped due to it's lack of a name (proc). The values I want to pass in are class level. Is that possible?

[Ola Tuvesson]

@choise: That should not happen: if project_id is present the or clause will ensure this is used - only if a project_id is not supplied will the id param be selected. In other words: when both parameters are supplied, the or clause ensures the correct value is used, as it will always prefer project_id. Naturally, you would not want to call this method when neither is present, or when there is no project_id but there is an id which does not reference a project.

[marcus3006]

@oreoshake: i have the same problem. Did you found a solution?

[Augustin Riedinger]

How can I do this with a :only or a :except rule, like before_filter { |c| c.authenticate_admin! params[:id] }, :only => [:edit, :update, :destroy] ?

[David Pelaez]

This answer is more elegant because the lambda defaults to the execution context of the class, hence private methods can be called without using '.send'

[David Pelaez]

The fact that passing the block requires using send means it's better to use a lambda as suggested in the answer of @vadym-tyemirov

[ahnbizcad]

@Vadym Tyemirov Is find_campaign the private method name? In param=params[:id], is param the name of the new local variable that will be passed as an argument to find_campaign? Meaning, that within the find_campaign private method itself, we use param not, params{:id]?

[Vadym Tyemirov]

find_campaign could be either, but I'd make it private to be sure we don't expose what is not consumed. params is a hash variable available to our methods, param is any variable that you'd need to pass to find_campaign method, e.g. before_action ->(campaign_id=params[:id]) { find_campaign(campaign_id) }, only: %i| show edit update destroy |

[ahnbizcad]

FYI to beginners: c in this case is the controller, and you're calling an instance method you define in this controller.