View Helpers

Instead of writing raw HTML, the Rails framework provides Ruby functions called view helpers that can write HTML on our behalf. Using view helpers often results in simpler code, and with more abilities than standard HTML elements can provide.

We will look at two such helper functions: form_tag and link_to.

form_tag

We use form_tag anywhere we would otherwise use a <form> element. Here is the general syntax. Note in particular the do...end block that encompasses the form controls.

<%= form_tag "/movies", method: "get" do %>
  <p>
    Search by title:
    <input type="text" name="keyword">
  </p>
  <button>Submit</button>
<% end %>

Unlike raw HTML, all four HTTP methods are supported:

HTTP method	Reason	Supported in HTML?
get	Retrieve data	Yes
post	Add new data	Yes
patch	Update existing data	Yes
delete	Delete existing data	Yes

Here's a typical form for updating a user's contact information:

<% user = User.find_by(last_name: 'Smith') %>

<%= form_tag "/users/#{user.id}", method: 'patch' do %>

  <p>
    First name: <input type="text" name="first_name" value="<%= user.first_name">
  </p>
  <p>
    Last name: <input type="text" name="last_name" value="<%= user.last_name">
  </p>
  <p>
    Address: <input type="text" name="address" value="<%= user.address">
  </p>
  <p>
    City: <input type="text" name="city" value="<%= user.city">
  </p>
  <p>
    State: <input type="text" name="state" value="<%= user.state">
  </p>
  <p>
    Zip: <input type="text" name="zip" value="<%= user.zip">
  </p>

<% end %>

LINK_TO

The HTML5 <a> element is easy to use but only supports the get method. Sometimes we would like links to trigger a database update instead.

Here's an example of how to implement a "Delete" link:

<% movie = Movie.find_by(title: 'Apollo 13') %>
<% ... %>

<%= link_to "Delete This Movie", "/movies/#{movie.id}", method: 'delete' %>

When the user clicks this link, an HTTP delete request will be sent to the application, triggering the destroy action in the MoviesController.