Rails API：一个请求，多个控制器操作

Question

I have multiple models that in practice are created and deleted together. Basically I have an Article model and an Authorship model. Authorships link the many to many relation between Users and Articles. When an Article is created, the corresponding Authorships are also created. Right now, this is being achieved by POSTing multiple times.

However, say only part of my request works. For instance, I'm on bad wifi and only the create article request makes it through. Then my data is in a malformed half created, half not state.

To solve this, I want to send all the data at once, then have Rails split up the data into the corresponding controllers. I've thought of a couple ways to do this. The first way is having controllers handle each request in turn, sort of chaining them together. This would require the controllers to call the next one in the chain. However, this seems sorta rigid because if I decide to compose the controllers in a different way, I'll have to actually modify the controller code itself.

The second way splits up the data first, then calls the controller actions with each bit of data. This way seems more clean to me, but it requires some logic either in the routing or in a layer independent of the controllers. I'm not really clear where this logic should go (another controller? Router? Middleware?)

Has anybody had experience with either method? Is there an even better way?

Thanks, Nicholas

Answer 1

Typically you want to do stuff like this -- creating associated records on object creation -- all in the same transaction. I would definitely not consider breaking up the creation of an Authorship and Article if creating an Authorship is automatic on Article creation. You want a single request that takes in all needed parameters to create an Article and its associated Authorship , then you create both in the same transaction. One way would be to do something like this in the controller:

class Authorship
  belongs_to :user
  belongs_to :article
end

class Article
  has_many :authorships
  has_many :users, through: :authorships
end

class ArticlesController
  def create
    @article = Article.new({title: params[:title], stuff: [:stuff]...})
    @article.authorships.build(article: @article, user_id: params[:user_id])
    if @article.save
      then do stuff...
    end
  end
end

This way when you hit @article.save , the processing of both the Article and the Authorship are part of the same transaction. So if something fails anywhere, then the whole thing fails, and you don't end up with stray/disparate/inconsistent data.

If you want to assign multiple authorships on the endpoint (ie you take in multiple user id params) then the last bit could become something like:

class ArticlesController
  def create
    @article = Article.new({title: params[:title], stuff: [:stuff]...})
    params[:user_ids].each do |id|
      @article.authorships.build(article: @article, user_id: id)
    end

    if @article.save
      then do stuff...
    end
  end
end

You can also offload this kind of associated object creation into the model via a virtual attribute and a before_save or before_create callback, which would also be transactional. But the above idiom seems more typical.

Answer 2

I would handle this in the model with one request. If you have a has_many relationship between Article and Author , you may be able to use accept_nested_attributes_for on your Article model. Then you can pass Authorship attributes along with your Article attributes in one request.

I have not seen your code, but you can do something like this:

model/article.rb

class Article < ActiveRecord::Base
   has_many :authors, through: :authorship # you may also need a class_name: param
   accepts_nested_attributes_for: :authors
end

You can then pass Author attributes to the Article model and Rails will create/update the Authors as required.

Here is a good blog post on accepts_nested_attributes_for. You can read about it in the official Rails documentation .

I would recommend taking advantage of nested attributes and the association methods Rails gives you to handle of this with one web request inside one controller action.