ActionController::ParamsWrapper in Rails is responsible for wrapping the parameters hash into a nested hash.
Recently while building a rest api for one of the applications I ran into an strange problem.
While making a
POST request with some JSON params, I observed that the request params were getting duplicated in an unusual manner for eg. when I made following request to a controller named
transactions with following params:
Here’s what I was getting in my controller as request params:
As we can see above the same params are getting duplicated, after searching a little while for what could be the reason for this, I got introduced to Rails’s ActionController::ParamsWrapper module.
Well in brief what this module does is that it wraps the parameters hash into a nested hash, which in turn allows us to submit requests without having to specify any root elements. Rails has it because it provides us an advantage as it wraps the parameters in a nested hash using the
controller-name as key by default (we can change this as well). So let’s say if we
enable ParamsWrapper for :json format then we don’t need to send JSON parameters like:
instead we can just send them as:
This functionality is enabled in wrap_parameters initializer of your app(
config/initializers/wrap_parameters.rb) and can be customized. Below is how
wrap_parameters is initialized by default when we create a new Rails app.
Rails has params wrapping on by default for
json, but if we don’t want our params to be wrapped we can either remove
json from the
format array which will turn off params wrapping for the whole application altogether. In case you want to do this for a specific controller,
transactions_controller in our example, it can be done by calling
wrap_parameters false in our controller.
- Customizing ParamsWrapper: ActionController::ParamsWrapper