Module | ActionView::Helpers::ActiveRecordHelper
In: | 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 way 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

error_message_on error_messages_for form input

### Public Instance methods

error_message_on(object, method, *args)

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 extended to include a `:prepend_text` and/or `:append_text` (to properly explain the error), and a `:css_class` to style it accordingly. `object` should either be the name of an instance variable or the actual object. The method can be passed in either as a string or a symbol. As an example, let‘s say you have a model `@post` that has an error message on the `title` attribute:

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

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

      <%= error_message_on "post", "title",
          :prepend_text => "Title simply ",
          :append_text => " (or it won't work).",
          :css_class => "inputError" %>

error_messages_for(*params)

Returns a string with a `DIV` containing all of the error messages for the objects located as instance variables by the names given. If more than one object is specified, the errors for the objects are displayed in the order that the object names are provided.

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").
- `:object` - The object (or array of objects) for which to display errors, if you need to escape the instance variable convention.
- `:object_name` - The object name to use in the header, or any text that you prefer. If `:object_name` is not set, the name of the first object will be used.
- `:header_message` - The message in the header of the error div. Pass `nil` or an empty string to avoid the header message altogether. (Default: "X errors prohibited this object from being saved").
- `:message` - The explanation message after the header message and before the error list. Pass `nil` or an empty string to avoid the explanation message altogether. (Default: "There were problems with the following fields:").

To specify the display for one object, you simply provide its name as a parameter. For example, for the `@user` model:

      error_messages_for 'user'

To specify more than one object, you simply list them; optionally, you can add an extra `:object_name` parameter, which will be the name used in the header message:

      error_messages_for 'user_common', 'user', :object_name => 'user'

If the objects cannot be located as instance variables, you can add an extra `:object` parameter which gives the actual object (or array of objects to use):

      error_messages_for 'user', :object => @question.user

NOTE: This is a pre-packaged presentation of the errors with embedded strings and a certain HTML structure. If what you need is significantly different from the default presentation, it makes plenty of sense to access the `object.errors` instance yourself and set it up. View the source of this method to see how easy it is.

form(record_name, options = {}) {|contents if block_given?| ...}

Returns an entire form with all needed input tags for a specified Active Record object. For example, if `@post` has attributes named `title` of type `VARCHAR` and `body` of type `TEXT` then

      form("post")

would yield a form like the following (modulus formatting):

      <form action='/posts/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"></textarea>
        </p>
        <input name="commit" 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. For example, if `@entry` has an attribute `message` of type `VARCHAR` then

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

would yield a form like the following (modulus formatting):

      <form action="/entries/sign" method="post">
        Message:
        <input id="entry_message" name="entry[message]" size="30" type="text" /><br />
        <input name="commit" 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

The following options are available:

- `:action` - The action used when submitting the form (default: `create` if a new record, otherwise `update`).
- `:input_block` - Specialize the output using a different block, see above.
- `:method` - The method used when submitting the form (default: `post`).
- `:multipart` - Whether to change the enctype of the form to "multipart/form-data", used when uploading a file (default: `false`).
- `:submit_value` - The text of the submit button (default: "Create" if a new record, otherwise "Update").

input(record_name, method, options = {})

Returns a default input tag for the type of object returned by the method. For example, if `@post` has an attribute `title` mapped to a `VARCHAR` column that holds "Hello World":

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

[Validate]