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 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, prepend_text = "", append_text = "", css_class = "formError")

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

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_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.

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 be the name in the header.

      error_messages_for 'user_common', 'user', :object_name => '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, let‘s say you have a table model `Post` with attributes named `title` of type `VARCHAR` and `body` of type `TEXT`:

      form("post")

That line would yield a form like the following:

        <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">
            </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. For example, let‘s say you have a model `Entry` with an attribute `message` of type `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

input(record_name, method, options = {})

Returns a default input tag for the type of object returned by the method. For example, let‘s say you have a model that has an attribute `title` of type VARCHAR column, and this instance holds "Hello World":

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

[Validate]