4.5 Shallow modules 浅模块

On the other hand, a shallow module is one whose interface is relatively complex in comparison to the functionality that it provides. For example, a class that implements linked lists is shallow. It doesn’t take much code to manipulate a linked list (inserting or deleting an element takes only a few lines), so the linked list abstraction doesn’t hide very many details. The complexity of a linked list interface is nearly as great as the complexity of its implementation. Shallow classes are sometimes unavoidable, but they don’t provide help much in managing complexity.

另一方面，浅层模块是其接口与其提供的功能相比相对复杂的模块。例如，实现链表的类很浅。操作链表不需要太多代码（插入或删除元素仅需几行），因此链表抽象不会隐藏很多细节。链表接口的复杂度几乎与其实现的复杂度一样高。浅类有时是不可避免的，但是它们在管理复杂性方面没有提供太多帮助。

Here is an extreme example of a shallow method, taken from a project in a software design class:

这是一个浅层方法的极端示例，该浅层方法来自软件设计类的项目：

  1. private void addNullValueForAttribute(String attribute) {
  2.     data.put(attribute, null);
  3. }

From the standpoint of managing complexity, this method makes things worse, not better. The method offers no abstraction, since all of its functionality is visible through its interface. For example, callers probably need to know that the attribute will be stored in the data variable. It is no simpler to think about the interface than to think about the full implementation. If the method is documented properly, the documentation will be longer than the method’s code. It even takes more keystrokes to invoke the method than it would take for a caller to manipulate the data variable directly. The method adds complexity (in the form of a new interface for developers to learn) but provides no compensating benefit.

从管理复杂性的角度来看，此方法会使情况变得更糟，而不是更好。该方法不提供任何抽象，因为其所有功能都可以通过其接口看到。例如，调用者可能需要知道该属性将存储在 data 变量中。考虑接口并不比考虑完整实现简单。如果正确记录了该方法，则文档将比该方法的代码长。与调用方直接操作数据变量相比，调用该方法所花费的击键甚至更多。该方法增加了复杂性（以供开发人员学习的新接口的形式），但没有提供任何补偿。

img Red Flag: Shallow Module img

A shallow module is one whose interface is complicated relative to the functionality it provides. Shallow modules don’t help much in the battle against complexity, because the benefit they provide (not having to learn about how they work internally) is negated by the cost of learning and using their interfaces. Small modules tend to be shallow.

浅层模块是一个接口相对于其提供的功能而言复杂的模块。浅层模块在对抗复杂性方面无济于事，因为它们提供的好处（不必了解它们在内部如何工作）被学习和使用其接口的成本所抵消。小模块往往很浅。