Fabrizio Bertoglio Fabrizio Bertoglio - 1 year ago 64
Ruby Question

Rails - strong params removing empty fields from nested attributes

I have been working on this line of code for three days.
I have the following strong params:

def location_params
params.require(:location).permit(:country, {:ads_attributes => [:remote, :days]})

The method param_clean will delete from the location_params the empty fields, but it will not work with the nested :ads_attributes.
The main reason is that param_clean can only be called on location_params that has class ActiveController::Parameters. I can not call on v the method param_clean

def param_clean
location_params.delete_if{ |k, v| v.empty? or v.instance_of?(ActionController::Parameters) && v.param_clean.empty? }

I receive the following error

undefined method `param_clean' for #<ActionController::Parameters:0x007f..>

This is the value of location_params

<ActionController::Parameters {"country"=>"", "ads_attributes"=><ActionController::Parameters {"remote"=>"0", "days"=>""} permitted: true>} permitted: true>

This is the value of
variable when the error is triggered

<ActionController::Parameters {"remote"=>"0", "days"=>""} permitted: true>

v.class => ActionController::Parameters

The method does not work with the nested parameters.
Thanks a lot for your help

Best Regards

Answer Source

The problem is that the param_clean method is not defined in ActionController::Parameters class. So, you have to change your approach, by either:

  • Extending ActionController::Parameters to include the method (not that I would recommend it).
  • Refactor the method. One way to do it would be as follows:

    def param_clean(_params)
      _params.delete_if do |k, v|
        if v.instance_of?(ActionController::Parameters)
    # how to use it
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