问用户子对象Rails 4上未定义的方法错误

EN

undefined method `transaction_kind' for nil:NilClass
app/models/transaction.rb:10:in `create_transaction'
app/controllers/transactions_controller.rb:17:in `create'

Parameters: {"utf8"=>"✓", "authenticity_token"=>"XXXXX", "transaction"=>{"transaction_kind"=>"Deposit", "user_id"=>"113", "credit"=>"99"}, "commit"=>"Submit Request", "lender_id"=>"113"}

class Transaction < ActiveRecord::Base
    belongs_to :user
    after_save :create_transaction
    attr_accessible :transaction_kind, :user_id, :credit, :debit, :created_at

    def create_transaction
    client = Restforce.new
    credit = '012c00000004k5A'
    debit = '012c00000004k55'
    if @transaction.transaction_kind == "Deposit"
        client.create!('Transaction__c', Account__c: self.salesforce_id, RecordTypeId: credit, Debit_Amount__c: self.debit, Credit_Amount__c: self.credit, Recorded_On__c: self.created_at, Status__c: 'New Transaction', Type: 'Deposit', Transaction_Type__c: self.transaction_kind)
    else
        client.create!('Transaction__c', Account__c: self.salesforce_id, RecordTypeId: debit, Debit_Amount__c: self.debit, Credit_Amount__c: self.credit, Recorded_On__c: self.created_at, Status__c: 'New Transaction', Type: 'Withdrawal', Transaction_Type__c: self.transaction_kind)
    end
  end 

end

<%= form_for [@user, @transaction], url: lender_transaction_path(@user) do |f| %>
  <%= f.hidden_field :transaction_kind, :value => "Deposit" %>
  <%= f.hidden_field :user_id, :value => @user.id %>
  <%= f.label :credit, :class => "required" %>
  <%= f.text_field :credit, :autofocus => :true, :class => "form-control margin-bottom-20 required"%>
  <%= f.submit 'Submit Request', :class => "btn-u btn-u-primary" %>
<% end %>

class TransactionsController < ApplicationController
    before_filter :authenticate_user!

    def new
        @user = current_user
        @transaction = Transaction.new
        if @user.activated?
            client = Restforce.new
            @account = client.find('Account', @user.salesforce_id, 'Account_Id')
            transaction_query = "select from  where Account__c ='%s' AND " % @account.Id.to_s
            @transactions = client.query(transaction_query)
        end 
    end

    def create
        @user = current_user
        @transaction = Transaction.create(transaction_params)
        if @transaction.save
            redirect_to new_lender_transaction_path(@user)
        end
    end

    private

        def transaction_params
            params.require(:transaction).permit(:transaction_kind, :credit, :debit, :created_at)
        end

end