保华的Rails学习笔记

form for do用法举例

While this is an increase in comfort it is far from perfect. If Person has many attributes to edit then we would be repeating the name of the edited object many times. What we want to do is somehow bind a form to a model object, which is exactly what form_for does.

Assume we have a controller for dealing with articles app/controllers/articles_controller.rb:

def new
  @article = Article.new
end

The corresponding view app/views/articles/new.html.erb using form_for looks like this:

<%= form_for @article, url: {action: "create"}, html: {class: "nifty_form"} do |f| %>
  <%= f.text_field :title %>
  <%= f.text_area :body, size: "60x12" %>
  <%= f.submit "Create" %>
<% end %>

There are a few things to note here:

@article is the actual object being edited.
There is a single hash of options. Routing options are passed in the :url hash, HTML options are passed in the :html hash. Also you can provide a :namespace option for your form to ensure uniqueness of id attributes on form elements. The namespace attribute will be prefixed with underscore on the generated HTML id.
The form_for method yields a form builder object (the f variable).
Methods to create form controls are called on the form builder object f.
The resulting HTML is:

<form accept-charset="UTF-8" action="/articles" method="post" class="nifty_form">
  <input id="article_title" name="article[title]" type="text" />
  <textarea id="article_body" name="article[body]" cols="60" rows="12"></textarea>
  <input name="commit" type="submit" value="Create" />
</form>

The name passed to form_for controls the key used in params to access the form's values. Here the name is article and so all the inputs have names of the form article[attribute_name]. Accordingly, in the create action params[:article] will be a hash with keys :title and :body. You can read more about the significance of input names in the parameter_names section.

The helper methods called on the form builder are identical to the model object helpers except that it is not necessary to specify which object is being edited since this is already managed by the form builder.

更多form for的用法请参考:http://guides.rubyonrails.org/form_helpers.html