Question

我添加了一个＆＃34; before_save＆＃34;我的模型在保存之前将一些逻辑应用于我的模型。当我使用此代码时，创建记录，然后立即更新（使用不正确的值）。如果我将其注释掉，则在创建新记录时没有后续更新。

模型

class Transaction < ApplicationRecord
belongs_to :account

attr_accessor :trx_type

before_save do
    if self.trx_type == "debit"
        self.amount = self.amount * -1
    end
end

end

控制器

class TransactionsController < ApplicationController
before_action :find_account
before_action :find_transaction, only: [:edit, :update, :show, :destroy]

# Index action to render all transactions
def index
    @transactions = @account.transactions

    respond_to do |format|
        format.html # index.html.erb
        format.xml  { render :xml => @transactions }
    end
end

# New action for creating transaction
def new
    @transaction = @account.transactions.build

    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @transaction }
    end
end

# Create action saves the trasaction into database
def create
    @transaction = @account.transactions.create(transaction_params)

    respond_to do |format|
        if @transaction.save
            format.html { redirect_to([@transaction.account, @transaction], :notice => 'Transaction was successfully created.') }
            format.xml  { render :xml => @transaction, :status => :created, :location => [@transaction.account, @transaction] }
        else
            format.html { render :action => "new" }
            format.xml  { render :xml => @transaction.errors, :status => :unprocessable_entity }
        end
    end
end

# Edit action retrieves the transaction and renders the edit page
def edit
end

  # Update action updates the transaction with the new information
def update
    respond_to do |format|
        if @transaction.update_attributes(transaction_params)
            format.html { redirect_to([@transaction.account, @transaction], :notice => 'Transaction was successfully updated.') }
            format.xml  { head :ok }
        else
            format.html { render :action => "edit" }
            format.xml  { render :xml => @transaction.errors, :status => :unprocessable_entity }
        end
    end
end

# The show action renders the individual transaction after retrieving the the id
def show
    respond_to do |format|
        format.html # show.html.erb
        format.xml  { render :xml => @transaction }
    end
end

# The destroy action removes the transaction permanently from the database
def destroy
    @transaction.destroy

    respond_to do |format|
        format.html { redirect_to(account_transactions_url) }
        format.xml  { head :ok }
    end
end

private

def transaction_params
    params.require(:transaction).permit(:trx_date, :description, :amount, :trx_type)
end

def find_account
    @account = current_user.accounts.find(params[:account_id])
end

def find_transaction
    @transaction = @account.transactions.find(params[:id])
end
end

控制台输出

Started POST "/accounts/1/transactions" for 127.0.0.1 at 2018-03-20 13:59:37 -0400
Processing by TransactionsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"kURRN8FaHmjrDU7y5cikBLREGZdMgHm4PsVUcOHxn7MAlqmi2zolA0LYOKQ46JkTzXl+Fkgj1O6SlBhVjdM5Qw==", "transaction"=>{"trx_type"=>"debit", "trx_date(1i)"=>"2018", "trx_date(2i)"=>"3", "trx_date(3i)"=>"20", "description"=>"Test 10", "amount"=>"132"}, "commit"=>"Create Transaction", "account_id"=>"1"}
  User Load (0.5ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT $2  [["id", 1], ["LIMIT", 1]]
  Account Load (0.5ms)  SELECT  "accounts".* FROM "accounts" WHERE "accounts"."user_id" = $1 AND "accounts"."id" = $2 LIMIT $3  [["user_id", 1], ["id", 1], ["LIMIT", 1]]
   (0.2ms)  BEGIN
  SQL (0.6ms)  INSERT INTO "transactions" ("trx_date", "description", "amount", "account_id", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5, $6) RETURNING "id"  [["trx_date", "2018-03-20"], ["description", "Test 10"], ["amount", "-132.0"], ["account_id", 1], ["created_at", "2018-03-20 13:59:37.349781"], ["updated_at", "2018-03-20 13:59:37.349781"]]
   (3.5ms)  COMMIT
   (0.1ms)  BEGIN


  SQL (0.3ms)  UPDATE "transactions" SET "amount" = $1, "updated_at" = $2 WHERE "transactions"."id" = $3  [["amount", "132.0"], ["updated_at", "2018-03-20 13:59:37.355748"], ["id", 27]]
   (0.9ms)  COMMIT
Redirected to http://localhost:3000/accounts/1/transactions/27
Completed 302 Found in 16ms (ActiveRecord: 6.6ms)

我是Rails的新手，并试图了解我的代码发生了什么。我提前感谢任何帮助。

谢谢！

Answer 1

这里有两件事让你有些悲伤，但他们很容易解决。

首先，在控制器的创建操作中，您实际上调用了两种将数据保存到数据库的方法，这就是为什么您在控制台输出中看到两个保存的原因。

方法的第一行负责第一次保存：

@transaction = @account.transactions.create(transaction_params)

这一行在你的respond_to块中负责第二次保存：

if @transaction.save

其次，记录在第一次保存中而不在第二次保存中具有正确amount的原因与您的事务模型的before_save回调中的逻辑有关。它正在使用amount并在其上调用* -1。由于第一次保存已经使金额为负数，因此第二次保存会将其重新设置为正数。

Answer 2

您似乎需要before_create因为您不太可能改变交易类型吗？

before_create do
  if self.trx_type == "debit"
    self.amount = self.amount * -1
  end
end

更新：看起来您需要在控制器中更改：

@transaction = @account.transactions.create(transaction_params)

到

@transaction = @account.transactions.build(transaction_params)

Ruby on Rails before_save在创建新记录后直接导致更新

2 个答案: