Rails-如何处理具有has_many关联错误的记录创建

Question

I am running into a problem when trying to handle a #create request on a model with a has_many association where one of the passed in IDs does not belong to an existing record.

Test request:

post authors_path, params: { book_ids: [-1] }

Controller method:

def create
  @author= Author.create params
end

Model:

class Author
  has_many :books
end

This results in an ActiveRecord::RecordNotFound error being raised.

The problem is as follows:

I am already rescuing from an ActiveRecord::RecordNotFound error and responding with 404 Record Not Found in my ApplicationController because such an error typically arises when a user is attempting to GET , PATCH , PUT , or DELETE a record that does not exist, eg, get author_path(-1) . I would prefer to avoid moving the rescue clause onto the #show , #create , etc methods because I have a lot of controllers, resulting in a lot of duplicate code.

I want to keep my record and association creations atomic and this seems to be the best way to do it, but I also want to respond with a 400 Bad Request when the situation described above occurs. What would be the best way to handle such a situation?

UPDATE

After some more research, I wrote a quick custom validation that validates a record exists for all passed in book_ids

class Author < ApplicationRecord  
  validate :books_exist  

  def books_exist  
    return if book_ids.blank?  
    Book.find book_ids
  rescue ActiveRecord::RecordNotFound => e  
    errors.add e.message  
  end  
end

This doesn't seem to work though as even instantiating a new Author instance without saving it to the database throws an ActiveRecord::RecordNotFound error:

> Author.new(association_ids: [-1])
  Book Load (2.3ms) SELECT `books`.* FROM `books` WHERE `books`.`id` = -1
ActiveRecord::RecordNotFound: Couldn't find Book with 'id'=[-1]
  from ...

The issue seems to be that ActiveRecord attempts to find a record for the passed in book_id before any validation occurs. Is there any way to rescue this error? It seems like there's not much of a workaround for this particular issue.

Answer 1

The two solutions that were suggest to me outside of StackOverflow are as follows:

1. Rescue the error in each controller action

    class AuthorsController def create @author = Author.create(params) render json: @author rescue ActiveRecord::RecordNotFound => e render json_error_message end end 

2. Create a generic action in the ApplicationController

    class ApplicationController def create(model) instance_variable_set("@#(model.class.name}", model.create(params) rescue ActiveRecord::RecordNotFound => e render json_error_message end end class AuthorsController def create super(Author) end end