Submitting form data is a common feature of web applications – allowing usersto submit their information and giving them feedback whether the information isvalid or not.

ActiveRecord comeswith a powerful set of validators for attributes on a persisted data model. Whendata is not persisted, or used for other non-active record purposes,ActiveModel Helper Modulesreduce the complexity of validations on your plain old Ruby objects.

Routing

Create the routes needed for displaying the form object and posting the data

• Restrict resources to the routes you need usingonly:

# config/routes.rbresources:registration,only:[:new,:create]

Controller and Actions

Create a controller withnew andcreate actions.

• respond_with will re-render thenew action if there are any validationerrors on the model
• If there are no errors on the model the visitor will be redirected toshowthe current resource. In this case the user will be redirected tosome_other_success_path

# app/controllers/registration_controller.rbclassRegistrationsController<ApplicationControllerrespond_to:htmldefnew@registration=Registration.newenddefcreate@registration=Registration.new(registration_params)@registration.registerrespond_with@registration,location:some_success_pathendprivatedefregistration_params# ...endend

View with Registration Form

The view renders a web form with fields to submit.

• Use the ActiveModel object@registration in the form
• Form generates the endpointregistration_path and method of deliverypost
• Validation errors will display inline within the form just like ActiveRecord

# app/views/registration/new.html.erb<%=form_for@registrationdo|f|%><%=f.label:first_name,'First Name'%>:<%=f.text_field:first_name%>  ...<%=f.submit%><%end%>

Object with ActiveModel Conversion, Naming, and Validations

Use any of theActiveRecordValidations inthe model.

• Command pattern used when callingregister method.
• ActiveRecord validation syntax on attributes.
• ActiveModel::Model mixin includes modules, and includes an initializationmethod.

# app/models/registration.rbclassRegistrationincludeActiveModel::Modelattr_accessor(:company_name,:email,:first_name,:last_name,:terms_of_service)validates:company_name,presence:truevalidates:email,presence:true,email:truevalidates:first_name,presence:truevalidates:last_name,presence:truevalidates:terms_of_service,acceptance:truedefregisterifvalid?# Do something interesting here# - create user# - send notifications# - log events, etc.endendprivatedefcreate_user# ...endend

Takeaways

• Keep business logic out of the Controller and Views
• Add validation support to plain Ruby object using ActiveModel includes
• Display data validation errors in the form
• Use ActiveModel naming conventions for generating form endpoints

• RESTful contact forms
• Build a (better) search form in Rails with Active Model
• Validation, Database Constraint, or Both?

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