如何在静态方法中使用依赖注入？ [英] How to use Dependency Injection with Static Methods?

问题描述

想象一下，有一个 Customer 类，它带有一个实例 Load（）方法。

Imagine there is a Customer class with an instance Load() method.

调用 Load（）方法时，它将通过以下方式检索订单详细信息：

When the Load() method is called, it retrieves order details by e.g.

var orders = Order.GetAll(customerId, ...);

GetAll（）是 Order 类和输入参数是在 Customer 类中定义的字段。

GetAll() is a static method of the Order class and the input parameters are fields defined in the Customer class.

如您所见， Order 是 Customer 类的依赖项，但是，我可以不仅要创建 IOrder 并将其注入那里，因为接口不能具有静态方法。

As you can see, Order is a dependency of the Customer class, however, I can't just create an IOrder and inject it there as interfaces can't have static methods.

因此，问题是如何在此示例中引入依赖注入？

Therefore, the question is how could I introduce dependency injection in this example?

我不想创建 GetAll（）实例方法，因为它是静态方法，需要保持这种状态。

I don't want to make GetAll() an instance method since it's a static method and need to keep it that way.

例如，我在设计中使用了实用工具类，其中大多数只包含静态方法

For example, I have used utility classes in my design, most of which just contain static methods.

推荐答案

如果您必须保留静态方法，我会将静态调用包装在存储库中

If you must keep the static method, I would wrap the static calls in a Repository object.

就像这样：

interface IOrderRepository {
   IEnumerable<IOrder> GetAll(customerId, ..);
}

class OrderRepository : IOrderRepository {
   IEnumerable<IOrder> GetAll(customerId, ...)
   {
     Order.GetAll(customerId,...); // The original static call.
   }
}

现在您将此存储库注入到 Customer 类。

Now you inject this repository into your Customer class.

（我假设您正在这样做，因此可以在运行时注入伪造的IOrder进行测试。应该说总体上来说，静态方法是测试的严重障碍。）

(I'm assuming you're doing this so you can inject fake IOrders at runtime for testing purposes. I should say that in general, static methods are a serious obstacle to testing.)

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