Rails Put vs Post

Question

I have been reading up on the difference between put and post requests and I have some related questions as it pertains to rails: I would like to change one specific field in an already created row...should I use a put or a post request? For example are the following different?

#Assume this is a put request
def update
    @model=Model.find(x)
    @model.field="new_field"
    @model.save
end

#Assume this is a post request
def update
    @model=Model.find(x)
    @model.field="new_field"
    @model.save
end

#What if I use the rails update method?
def update
    @model=Model.find(x)
    @model.update(model_params)
    @model.save
end

Thanks in advance.

Answer 1

According to rails convention,

PUT is used for updating an existing resource

POST is used for creating a new resource

In rails 4, PUT has been changed to PATCH to avoid confusion.

Rails generated routes will look like below by default

    posts GET    /posts(.:format)                            {:action=>"index", :controller=>"posts"}
          POST   /posts(.:format)                            {:action=>"create", :controller=>"posts"}
 new_post GET    /posts/new(.:format)                        {:action=>"new", :controller=>"posts"}
edit_post GET    /posts/:id/edit(.:format)                   {:action=>"edit", :controller=>"posts"}
     post GET    /posts/:id(.:format)                        {:action=>"show", :controller=>"posts"}
          PUT    /posts/:id(.:format)                        {:action=>"update", :controller=>"posts"}
          DELETE /posts/:id(.:format)                        {:action=>"destroy", :controller=>"posts"}

Notice the action for PUT and POST