How to understand load_resource and authorize_resource methods of cancancan gem?

问题

I am using the cancancan gem in my rails application. But I am not much clear for the meaning of load_and_authorize_resource method. I know this is the same as calling load_resource and authorize_resource.

load_resource will create a new instance of a model, or get a instance by params[:id], or a collection of instances, then authorize_resource method will use these instances to authorize. But if I already have a Model.find(params[:id]) or Model.new in each controller action, dose I need to add load_resource method?

For some action（Non RESTful actions) , they don't have relationship with model, so I don't need to get a instance, for this situation, authorize_resource how to work normally?

Any idea is appreciate! Thanks in advance!

回答1:

The load_and_authorize_resource sets a before_filter for each action to load the resource into an instance variable and authorize it automatically. So this is useful for RESTful actions. Now if you have Non RESTful actions in the same controller which can't load the resource you can do:

load_and_authorize_resource only: [:index, :show]

OR

skip_load_resource only: :new

This will skip the before_filter for those actions.

And if you have Model.find(params[:id]) in controller either you can remove that or just use:

authorize_resource

You will not need the load_resource for these actions. The load_resource also does the same thing which you have done manually. It just adds a before_action to all the actions and finds the object according to id.

And the load_resource will always provide you the instance variable with the same name of Model, so if you are using something different in your views for you object then it won't help too. So choosing an option will depend on you and your code.

Cancancan Wiki:

As of CanCan 1.5 you can use the skip_load_and_authorize_resource, skip_load_resource or skip_authorize_resource methods to skip any of the applied behaviour and specify specific actions like in a before filter.

Hope this helps.

来源：https://stackoverflow.com/questions/36075500/how-to-understand-load-resource-and-authorize-resource-methods-of-cancancan-gem