Ruby異常優秀實踐

Question

這是在Ruby中使用異常的好習慣嗎？ （如果object.nil引發ArgumentError的用法）

我應該在這裏刪除ArgumentError嗎？或者編寫自定義異常，如ProductNilError，QuantityMustBeMoreThanZeroError？

def create_order(product, options = { quantity: 1, guests: nil, confirmation_needed: false }) 
    raise ArgumentError, 'product is nil' if product.nil? 

    guests = options.has_key?(:guests) ? options[:guests] : nil 
    quantity = options.has_key?(:quantity) ? options[:quantity] : nil 
    confirmation_needed = options.has_key?(:confirmation_needed) ? options[:confirmation_needed] : nil 

    raise ArgumentError, 'quantity must be > 0' if quantity.nil? || quantity < 0 || quantity == 0 
    raise ArgumentError, 'product of beneficiary_type need guests' if product.is_a_beneficiary_type? && guests.nil? 
    raise ArgumentError, 'guests do not respond_to each (not an array)' if !guests.nil? && !guests.respond_to?(:each) 
    raise ArgumentError, 'product of quantity_type do not need guests' if product.is_a_quantity_type? && !guests.nil? 

    begin 
     order = build_order(guests, product) 
     debit_stock(quantity) 
     pay(order, product, quantity) 
     confirm_order(order) 
    ensure 
     rollback(order, quantity) 
    end 
    end 

Answer 1

由於這是在意見建議，我會鼓勵你使用ActiveRecord驗證：

http://guides.rubyonrails.org/active_record_validations.html

這裏你的問題問一個例子：

class Order < ActiveRecord::Base 
    validates :product, presence: true 
    validates :quantity, numericality: { greater_than: 0 } 
    validate :beneficiary_type 

    def beneficiary_type 
    return true unless product.is_a_beneficiary_type? && guests.nil? 
    errors.add(:guests, 'product of beneficiary_type need guests.') 
    end 
end 

當您創建Order實例時，您可以執行這些驗證。一個例子可能是在控制器創建動作：

def create 
    permitted = permitted_params # permit some params 
    @order.new(permitted) 
    if @order.valid? 
    @oder.save! 
    flash[:success] = "Order #{@order.id} has been created!" 
    redirect_to action: :index 
    else 
    render action: :new 
    end 
end