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Auto checking forms

Posted by Sandro Paganotti in Ruby on Rails - comments are closed

Sometimes it happens that the form we ask the user to fill is not releated to a model, for example we may just want to use the information provided to send an email message. If this occurs more than once in our application, we could create a quite smart structure to handle different forms in the same way.

First of all we need to structure our form in order to specify for each field if it is required or not; to do this we can use the already tested and implemented hash-like params structure simply by adding another level of depth:

  
  
 
required fields must be putted under [obb] level 
<%= text_field_tag "form_fields[obb][name]", get_from_params(params[:form_fields],:obb,:name) %> 
 
optional fields  must be putted under [fac] level 
<%= text_field_tag "form_fields[fac][name]", get_from_params(params[:form_fields],:fac,:name) %> 

The 'get_from_params' helper function does exactly the same as 'params[:form_fields][:fac][:name]' plus it checks that params[:form_fields][:fac] is not blank, preventig in this way the thrown of an exception.

 
 
   def get_from_params(param,stato,nome)
    return param[stato][nome] unless param.blank? or param[stato].blank?
    return nil
  end
 

Now we just need to check in our controller if the fields under the [obb] section are filled:

 
# put this inside the controller at which the forms refer
 
    errors = []
    if params[:form_fields][:obb].blank?
       flash[:notice] = "All the required fields are missing".t
       # ERROR - none of the required fields has been filled
       return
    end
    params[:form_fields][:obb].each_pair do |key,value|
      errors << "field #{key} is required".t if params[:form_fields][:obb][key.to_sym].blank? 
    end
    if errors.length > 0
      flash[:notice] = errors.join(" and ").capitalize
      # ERROR - some required fields are missing
      return
    end
    
    # NOERROR - Everithing went fine
 

What's missing here is a way to ensure that the user cannot alter your required fields list by using a tool such firebug; a solution could be adding an hidden field in each form containing a digest (ie: MD5) created by using a secret word plus all of the names of the required fields of that form (eg "mysecretw" + "name" + "email").

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