How do you add a custom HTTP response header in Rails?

In Rails, adding custom HTTP response headers is a straightforward process. This can be achieved in the controller's action using the response object. Below are specific steps and examples:

Step 1: Determine in which controller and action to add the custom header

First, determine in which controller and specific action you need to add the custom header. This typically depends on your business requirements. For example, you might want to add security or version control headers when returning specific API call results.

Step 2: Edit the corresponding action to add the custom header

Open the controller file and, in the action where you want to add the header, use the response.set_header method to set the custom header. This method takes two parameters: the header name and value.

Example Code

Assume we want to add a custom header in the show action of a controller named ProductsController:

ruby
class ProductsController < ApplicationController
  def show
    @product = Product.find(params[:id])

    # Add custom HTTP header
    response.set_header('X-Custom-Header', 'CustomValue')

    respond_to do |format|
      format.html # show.html.erb
      format.json { render json: @product }
    end
  end
end

In this example, we add a header named X-Custom-Header with the value CustomValue to the response.

Step 3: Test

Once you've added the custom header, test the change in the development environment. You can use browser developer tools or API testing tools like Postman to verify that the HTTP response headers include your custom header. Writing automated tests with Rails' built-in testing tools is also a good practice to ensure that the custom header settings are not accidentally removed or broken in future development:

ruby
test "should get show with custom header" do
  get product_url(products(:one))
  assert_response :success
  assert_equal 'CustomValue', @response.headers['X-Custom-Header']
end

By following these steps, you can flexibly add and manage custom HTTP response headers in your Rails application. This is useful for controlling caching strategies, security measures, or providing additional metadata.