Rails：在创建父级后创建 belongs_to 关联 class

Question

在我的应用中，用户填写表单并创建父级 class - 成本

稍后，我希望用户能够返回以添加关联 class - 成本依赖性。

所以用户被导航到 /costs/3/cost_dependencies/new

当我尝试在我的视图中引用 @cost 时，我得到一个 nil class 错误，所以我添加了 @cost=Cost.find(param[:id]) 以在我的控制器中访问它。

现在我遇到 Couldn't find Cost with id= 错误

只是一片空白。

Answer 1

假设您设置了嵌套路由，例如：

resources :costs do
  resources :cost_dependencies
end

然后成本 ID 将可用为 params[:cost_id]，您可以通过运行 rake routes 确认。您应该会看到如下内容：

              cost_cost_dependencies GET      /costs/:cost_id/cost_dependencies(.:format)                                        cost_dependencies#index
                                     POST     /costs/:cost_id/cost_dependencies(.:format)                                        cost_dependencies#create
            new_cost_cost_dependency GET      /costs/:cost_id/cost_dependencies/new(.:format)                                    cost_dependencies#new
           edit_cost_cost_dependency GET      /costs/:cost_id/cost_dependencies/:id/edit(.:format)                               cost_dependencies#edit
                cost_cost_dependency GET      /costs/:cost_id/cost_dependencies/:id(.:format)                                    cost_dependencies#show
                                     PATCH    /costs/:cost_id/cost_dependencies/:id(.:format)                                    cost_dependencies#update
                                     PUT      /costs/:cost_id/cost_dependencies/:id(.:format)                                    cost_dependencies#update
                                     DELETE   /costs/:cost_id/cost_dependencies/:id(.:format)                                    cost_dependencies#destroy
                               costs GET      /costs(.:format)                                                                   costs#index
                                     POST     /costs(.:format)                                                                   costs#create
                            new_cost GET      /costs/new(.:format)                                                               costs#new
                           edit_cost GET      /costs/:id/edit(.:format)                                                          costs#edit
                                cost GET      /costs/:id(.:format)                                                               costs#show
                                     PATCH    /costs/:id(.:format)                                                               costs#update
                                     PUT      /costs/:id(.:format)                                                               costs#update
                                     DELETE   /costs/:id(.:format)                                                               costs#destroy

因此，在您的控制器中使用以下内容：

@cost = Cost.find(param[:cost_id])

Rails：在创建父级后创建 belongs_to 关联 class

Rails: creating belongs_to associative class after parent has been created

ruby-on-rails

associations