Content negotiation trong Rails — `respond_to` và `respond_with` dùng như thế nào?

Content negotiation cho phép một action phản hồi theo format khác nhau (HTML, JSON, XML) tùy Accept header hoặc URL extension.

class PostsController < ApplicationController
  def show
    @post = Post.find(params[:id])

    respond_to do |format|
      format.html  # render app/views/posts/show.html.erb
      format.json { render json: @post }
      format.xml  { render xml: @post }
    end
  end
end

Request GET /posts/1 → HTML. GET /posts/1.json hoặc header Accept: application/json → JSON.

respond_with (từ gem responders) ngắn gọn hơn cho CRUD chuẩn nhưng ít tùy biến hơn. Với Rails API mode (ActionController::API), response mặc định là JSON và không cần respond_to.

Content negotiation lets a single action respond in different formats (HTML, JSON, XML) based on the Accept header or URL extension.

class PostsController < ApplicationController
  def show
    @post = Post.find(params[:id])

    respond_to do |format|
      format.html  # renders app/views/posts/show.html.erb
      format.json { render json: @post }
      format.xml  { render xml: @post }
    end
  end
end

GET /posts/1 → HTML. GET /posts/1.json or Accept: application/json header → JSON.

respond_with (via the responders gem) is more concise for standard CRUD but less flexible. In Rails API mode (ActionController::API), JSON is the default and respond_to is usually unnecessary.