Module ActionView::Helpers::ActiveRecordHelper
In: vendor/rails/actionpack/lib/action_view/helpers/active_record_helper.rb

The Active Record Helper makes it easier to create forms for records kept in instance variables. The most far-reaching is the form method that creates a complete form for all the basic content types of the record (not associations or aggregations, though). This is a great of making the record quickly available for editing, but likely to prove lackluster for a complicated real-world form. In that case, it’s better to use the input method and the specialized form methods in classes/ActionView/Helpers/FormHelper.html

Methods

Public Instance methods

Returns a string containing the error message attached to the method on the object, if one exists. This error message is wrapped in a DIV tag, which can be specialized to include both a prepend_text and append_text to properly introduce the error and a css_class to style it accordingly. Examples (post has an error message "can’t be empty" on the title attribute):

  <%= error_message_on "post", "title" %> =>
    <div class="formError">can't be empty</div>

  <%= error_message_on "post", "title", "Title simply ", " (or it won't work)", "inputError" %> =>
    <div class="inputError">Title simply can't be empty (or it won't work)</div>

[Source]

    # File vendor/rails/actionpack/lib/action_view/helpers/active_record_helper.rb, line 87
87:       def error_message_on(object, method, prepend_text = "", append_text = "", css_class = "formError")
88:         if errors = instance_variable_get("@#{object}").errors.on(method)
89:           content_tag("div", "#{prepend_text}#{errors.is_a?(Array) ? errors.first : errors}#{append_text}", :class => css_class)
90:         end
91:       end

Returns a string with a div containing all the error messages for the object located as an instance variable by the name of object_name. This div can be tailored by the following options:

  • header_tag - Used for the header of the error div (default: h2)
  • id - The id of the error div (default: errorExplanation)
  • class - The class of the error div (default: errorExplanation)

[Source]

     # File vendor/rails/actionpack/lib/action_view/helpers/active_record_helper.rb, line 99
 99:       def error_messages_for(object_name, options = {})
100:         options = options.symbolize_keys
101:         object = instance_variable_get("@#{object_name}")
102:         unless object.errors.empty?
103:           content_tag("div",
104:             content_tag(
105:               options[:header_tag] || "h2",
106:               "#{pluralize(object.errors.count, "error")} prohibited this #{object_name.to_s.gsub("_", " ")} from being saved"
107:             ) +
108:             content_tag("p", "There were problems with the following fields:") +
109:             content_tag("ul", object.errors.full_messages.collect { |msg| content_tag("li", msg) }),
110:             "id" => options[:id] || "errorExplanation", "class" => options[:class] || "errorExplanation"
111:           )
112:         end
113:       end

Returns an entire form with input tags and everything for a specified Active Record object. Example (post is a new record that has a title using VARCHAR and a body using TEXT):

  form("post") =>
    <form action='/post/create' method='post'>
      <p>
        <label for="post_title">Title</label><br />
        <input id="post_title" name="post[title]" size="30" type="text" value="Hello World" />
      </p>
      <p>
        <label for="post_body">Body</label><br />
        <textarea cols="40" id="post_body" name="post[body]" rows="20">
          Back to the hill and over it again!
        </textarea>
      </p>
      <input type='submit' value='Create' />
    </form>

It’s possible to specialize the form builder by using a different action name and by supplying another block renderer. Example (entry is a new record that has a message attribute using VARCHAR):

  form("entry", :action => "sign", :input_block =>
       Proc.new { |record, column| "#{column.human_name}: #{input(record, column.name)}<br />" }) =>

    <form action='/post/sign' method='post'>
      Message:
      <input id="post_title" name="post[title]" size="30" type="text" value="Hello World" /><br />
      <input type='submit' value='Sign' />
    </form>

It’s also possible to add additional content to the form by giving it a block, such as:

  form("entry", :action => "sign") do |form|
    form << content_tag("b", "Department")
    form << collection_select("department", "id", @departments, "id", "name")
  end

[Source]

    # File vendor/rails/actionpack/lib/action_view/helpers/active_record_helper.rb, line 59
59:       def form(record_name, options = {})
60:         record = instance_variable_get("@#{record_name}")
61: 
62:         options = options.symbolize_keys
63:         options[:action] ||= record.new_record? ? "create" : "update"
64:         action = url_for(:action => options[:action], :id => record)
65: 
66:         submit_value = options[:submit_value] || options[:action].gsub(/[^\w]/, '').capitalize
67: 
68:         contents = ''
69:         contents << hidden_field(record_name, :id) unless record.new_record?
70:         contents << all_input_tags(record, record_name, options)
71:         yield contents if block_given?
72:         contents << submit_tag(submit_value)
73: 
74:         content_tag('form', contents, :action => action, :method => 'post')
75:       end

Returns a default input tag for the type of object returned by the method. Example (title is a VARCHAR column and holds "Hello World"):

  input("post", "title") =>
    <input id="post_title" name="post[title]" size="30" type="text" value="Hello World" />

[Source]

    # File vendor/rails/actionpack/lib/action_view/helpers/active_record_helper.rb, line 20
20:       def input(record_name, method)
21:         InstanceTag.new(record_name, method, self).to_tag
22:       end

[Validate]