Rails Controller-“响应格式” html和json的目的是什么？

Question

Ruby on Rails Question: Inside the controller you have seven REST actions. Almost all of them have respond to do format xml/html or json. I have no idea what this means. Can you please explain it's purpose. For example:

def index
  @tweets = Tweet.all

  respond_to do |format|
   format.html
   format.json { render json: @tweets }
  end
end

What is the purpose of the "respond to" part that contains the html and json? What do these formats do? Also, what is the difference between xml and html? Sometimes I see xml and other times html.

Thank you

Answer 1

Its just a way of telling your controller how to respond to different request types . For example your client could want html or xml information from you:

def index
 @people = Person.find(:all)

  respond_to do |format|
    format.html
    format.xml { render :xml => @people.to_xml }
  end
end

What that says is, "if the client wants HTML in response to this action, just respond as we would have before, but if the client wants XML, return them the list of people in XML format." (Rails determines the desired response format from the HTTP Accept header submitted by the client.)

http://apidock.com/rails/ActionController/MimeResponds/InstanceMethods/respond_to