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 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>

error_messages_for(object_name, options = {})

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)

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 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

input(record_name, method, options = {})

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" />

[Validate]