我对 Rails 很陌生，我写了一个跟踪贷款的小应用程序。有一个用户模型和一个贷款模型，我已经计算出跟踪谁借了谁的钱等等。
我正在尝试编写一个新功能来跟踪付款，但我不确定我应该把它放在哪里。此功能将使用新值更新贷款金额的数据库值。这个功能会是 Loan 类的一部分吗？它会是一个可以访问贷款/用户模型的新控制器吗？
如果这个问题过于含糊，我很抱歉，我可以提供更多信息。
【问题讨论】：
标签： ruby-on-rails model-view-controller models controllers
您可以在贷款模型make_payment(amount) 中创建一个方法，然后从总贷款金额中减少金额。
我建议您保留付款日志，以便以后跟踪它们。创建一个属于Loan 模型的Payment 模型。
【讨论】：
当您获得一笔不小的贷款时，常见的情况是您获得了一个分期付款的付款计划。
每期可分多次付款。
让我们看看模型的外观：
class User < ActiveRecord::Base
has_many :loans
has_many :instalments, through: :loans
has_many :payments, through: :loans
end
# [int, foreign_key, index] user_id
# [float] total_amount - does not change!
class Loan < ActiveRecord::Base
belongs_to :user
has_many :instalments
has_many :payments
end
# [int, foreign_key, index] loan_id
# [float] total_due
# [float] payed
# [datetime] due_date
class Instalment < ActiveRecord::Base
belongs_to :loan
has_one :user, through: :loan
has_many :payments
end
# [int, foreign_key, index] instalment_id
# [float] amount
class Payment < ActiveRecord::Base
belongs_to :instalment
has_one :loan, through: :instalment
has_one :user, through: :loan
end
这可能看起来过于复杂，但实际上足以承担某种财务责任。我们可以跟踪用户每个月应该支付多少 - 以及哪些支付与特定的分期付款相关联。如果您真的想真正使用这个应用程序，您很可能会遇到更多的法律责任要求（除非您的目标是瑞士市场）。
让我们在这里谈谈应用程序流程：
请注意，在此域模型中，我们不会在创建后更新贷款金额 - 它只是他们借入的原始金额的记录（请记住，出于会计目的，您应该始终保留数据）。
我们不必计算还剩下多少贷款，而是将instalments.payed 列相加：
# [int, foreign_key, index] user_id
# [float] total_amount - does not change!
class Loan < ActiveRecord::Base
belongs_to :user
has_many :instalments
has_many :payments
def payed
installments.sum(:payed)
end
def amount_due
total_amount - installments.sum(:payed)
end
end
这是您需要的路线：
resources :users, shallow: true do
resources :loans
end
resources :loans, only: [], shallow: true do
resources :instalments
end
resources :instalments, only: [], shallow: true do
resources :payments
end
$ rake routes
Prefix Verb URI Pattern Controller#Action
user_loans GET /users/:user_id/loans(.:format) loans#index
POST /users/:user_id/loans(.:format) loans#create
new_user_loan GET /users/:user_id/loans/new(.:format) loans#new
edit_loan GET /loans/:id/edit(.:format) loans#edit
loan GET /loans/:id(.:format) loans#show
PATCH /loans/:id(.:format) loans#update
PUT /loans/:id(.:format) loans#update
DELETE /loans/:id(.:format) loans#destroy
loan_instalments GET /loans/:loan_id/instalments(.:format) instalments#index
POST /loans/:loan_id/instalments(.:format) instalments#create
new_loan_instalment GET /loans/:loan_id/instalments/new(.:format) instalments#new
edit_instalment GET /instalments/:id/edit(.:format) instalments#edit
instalment GET /instalments/:id(.:format) instalments#show
PATCH /instalments/:id(.:format) instalments#update
PUT /instalments/:id(.:format) instalments#update
DELETE /instalments/:id(.:format) instalments#destroy
instalment_payments GET /instalments/:instalment_id/payments(.:format) payments#index
POST /instalments/:instalment_id/payments(.:format) payments#create
new_instalment_payment GET /instalments/:instalment_id/payments/new(.:format) payments#new
edit_payment GET /payments/:id/edit(.:format) payments#edit
payment GET /payments/:id(.:format) payments#show
PATCH /payments/:id(.:format) payments#update
PUT /payments/:id(.:format) payments#update
DELETE /payments/:id(.:format) payments#destroy
【讨论】：