Question

在我的电子商务脚本中，可以将同一产品添加到购物车中，我该如何防止呢？

def add
    @cart.save if @cart.new_record?
    session[:cart_id] = @cart.id
    product = Product.find(params[:id])
    LineItem.create! :order => @cart, :product => product, :price => product.price
    @cart.recalculate_price!
    flash[:notice] = "Item added to cart!"
    redirect_to '/cart'
  end

Answer 1

在Cart.product_id上添加uniqueness验证，并根据Cart.id进行范围界定：

class Cart < ApplicationRecord
  validates :product_id, uniqueness: {scope: :id}
end

但要注意race conditions。

更新：如果没有实际的Cart模型向LineItem添加验证：

class LineItem < ApplicationRecord
  validates :product_id, uniqueness: {scope: :order_id}
end

更新2：使用add重构find_or_initialize_by方法：

def add
  @cart.save if @cart.new_record?
  session[:cart_id] = @cart.id
  product = Product.find(params[:id])
  line_item = LineItem.find_or_initialize_by(order:   @cart,
                                             product: product)
  line_item.price = product.price
  line_item.save!
  @cart.recalculate_price!
  flash[:notice] = "Item added to cart!"
  redirect_to '/cart'
end

更新3：检查product是否存在：

def add
  @cart.save if @cart.new_record?
  session[:cart_id] = @cart.id
  product = Product.find(params[:id])
  line_item = LineItem.find_by(order: @cart, product: product)
  if line_item
   notice = "ERROR: Product already in the cart"
  else   
   LineItem.create!(order:   @cart,
                    product: product,
                    price:   product.price)
   @cart.recalculate_price!
   notice = "Item added to cart!"
  end
  flash[:notice] = notice
  redirect_to '/cart'
end

如何防止将同一产品添加到购物车

1 个答案: