CODEWITHSUNDEEP
ruby-on-railsformsvalidation
Sarah Vessels
Sarah Vessels

Reputation: 31660

Rails form validation

I have a Rails app that lets a user construct a database query by filling out an extensive form. I wondered the best practice for checking form parameters in Rails. Previously, I have had my results method (the one to which the form submits) do the following:

if params[:name] && !params[:name].blank?
  @name = params[:name]
else
  flash[:error] = 'You must give a name'
  redirect_to :action => 'index'
  return
end

But for several form fields, seeing this repeated for each one got tiresome. I couldn't just stick them all in some loop to check for each field, because the fields are set up differently:

Etc. This was also repetitive, because I was setting flash[:error] for each missing/invalid parameter, and redirecting to the same URL for each one. I switched to using a before_filter that checks for all necessary form parameters and only returns true if everything's okay. Then the my results method continues, and variables are just assigned flat-out, with no checking involved:

@name = params[:name]

In my validate_form method, I have sections of code like the following:

if (
  params[:analysis_type][:to_s] == 'development' ||
  params[:results_to_generate].include?('graph')
)
  {:graph_type => :to_s, :graph_width => :to_s,
   :theme => :to_s}.each do |key, sub_key|
    unless params[key] && params[key][sub_key]
      flash[:error] = "Cannot leave '#{Inflector.humanize(key)}' blank"
      redirect_to(url)
      return false
    end
  end
end

I was just wondering if I'm going about this in the best way, or if I'm missing something obvious when it comes to parameter validation. I worry this is still not the most efficient technique, because I have several blocks where I assign a value to flash[:error], then redirect to the same URL, then return false.

Edit to clarify: The reason I don't have this validation in model(s) currently is for two reasons:

Edit to show improved technique: I make use of application-specific exceptions now, thanks to Jamis Buck's Raising the Right Exception article. For example:

def results
  if params[:name] && !params[:name].blank?
    @name = params[:name]
  else
    raise MyApp::MissingFieldError
  end

  if params[:age] && !params[:age].blank? && params[:age].numeric?
    @age = params[:age].to_i
  else
    raise MyApp::MissingFieldError
  end
rescue MyApp::MissingFieldError => err
  flash[:error] = "Invalid form submission: #{err.clean_message}"
  redirect_to :action => 'index'
end

Upvotes: 22

Views: 53056

Answers (4)

zawhtut
zawhtut

Reputation: 8561

Model

class Person 
    include ActiveModel::Validations
    include ActiveModel::Conversion
    extend ActiveModel::Naming

    attr_accessor :name
    attr_accessor :email


    validates_presence_of :name,:message => "Please Provide User Name"
    validates_presence_of :email,:message => "Please Provide Email"
end

Note that you don't necessarily need to save/persist the model to validate.

Controller

@person.name= params["name"]
@person.email= params["email"]
@person.valid?

One you called .valid? method on the model, the errors will be populated inside @person object. Hence,

View

<%if @person.errors.any? %>
     <%@person.errors.messages.each do|msg| %>
          <div class="alert alert-danger">
            <%=msg[0][1]%>
          </div>
     <%end%>
<%end%>

Upvotes: 1

weston
weston

Reputation: 2057

If you were to tackle the problem again today, you could create a model for the query parameter set and use Rails' built in validations, Rails 3 makes this a lot easier with ActiveModel::Validations see this post.

Upvotes: 2

casey
casey

Reputation:

You could try active_form (http://github.com/cs/active_form/tree/master/lib/active_form.rb) - just ActiveRecord minus the database stuff. This way you can use all of AR's validation stuff and treat your form like you would any other model.

class MyForm < ActiveForm
  validates_presence_of :name
  validates_presence_of :graph_size, :if => # ...blah blah 
end

form = MyForm.new(params[:form])
form.validate
form.errors

Upvotes: 25

Jamal Hansen
Jamal Hansen

Reputation: 954

Looks like you are doing the validation in the controller, try putting it in the model, it's better suited to that sort of thing.

Upvotes: 8

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