Form Builder

I want to introduce the basic of how to use form builder in rails. If we have a basic title and description page, if we submit the form without no content, we hope it will show some error message. the haml file will looks like this.

  %section.new_todo
    %h3 Add a new todo
    = form_for @todo do |f|
      = f.label :name, "Name"
      = f.text_Filed :name
      = f.label :description, "Description"
      = f.text_area :description, rows: 6
    %br
    = f.submit "Add this Todo"

Of course you can write if @todo.errors?, then render all the errors out.

But you can put a my_form_builder.rb file in the helpers:

  class MyFormBuilder < ActionView::Helper::FOrmBuilder
    def label(method, text = nil, options = {}, &block)
      errors = object.errors[method.to_sym] #object points to @todo in this case. see more if rails doc.
      if errors
        text += "<span class=\"error\">#{errors.first}</span>"
      end
      super(method, text.html_safe, options, &block)
    end
  end

  %section.new_todo
    %h3 Add a new todo
    = form_for @todo, builder: MyFormBuilder do |f|
      = f.label :name, "Name"
      = f.text_Filed :name
      = f.label :description, "Description"
      = f.text_area :description, rows: 6
    %br
    = f.submit "Add this Todo"

But you have to implement it in every form_for. If you want every form_for you use this feature, you can write your own form_for in application_helper.rb

if you take a look at rails doc:

form_for(record, options = {}, &block) Creates a form that allows the user to create or update the attributes of a specific model object.

It need record, options, &proc. So we create our own form_for also takes this three parameter. But we use ruby hash method: merge!, to put builder directly inside the options hash:

  module ApplicationHelper
    def my_form_for(record, options = {}, &proc)
      form_for(record, otpions.merge!({builder: MyFormBuilder}), &proc)
    end
  end

Custom Form Builder

formtastic

simple_form:

• simple_form_for
• integrate bootstrap, foundation
• lots of customization
• default mappings
• complex.

rails-bootstrap-forms:

• use f.alert_message to show error
• also work with bootstrap
• easy to go
• like original rails form