14.4 Use names consistently 一致使用名称

The second important property of good names is consistency. In any program there are certain variables that are used over and over again. For example, a file system manipulates block numbers repeatedly. For each of these common usages, pick a name to use for that purpose, and use the same name everywhere. For example, a file system might always use fileBlock to hold the index of a block within a file. Consistent naming reduces cognitive load in much the same way as reusing a common class: once the reader has seen the name in one context, they can reuse their knowledge and instantly make assumptions when they see the name in a different context.

好的名称的第二个重要属性是一致性。在任何程序中，都会反复使用某些变量。例如，文件系统反复操作块号。对于每种常见用法，请选择一个用于该目的的名称，并在各处使用相同的名称。例如，文件系统可能总是使用 fileBlock 来保存文件中块的索引。一致的命名方式与重用普通类的方式一样，可以减轻认知负担：一旦读者在一个上下文中看到了该名称，他们就可以重用其知识并在不同上下文中看到该名称时立即做出假设。

Consistency has three requirements: first, always use the common name for the given purpose; second, never use the common name for anything other than the given purpose; third, make sure that the purpose is narrow enough that all variables with the name have the same behavior. This third requirement was violated in the file system bug at the beginning of the chapter. The file system used block for variables with two different behaviors (file blocks and disk blocks); this led to a false assumption about the meaning of a variable, which in turn resulted in a bug.

一致性具有三个要求：首先，始终将通用名称用于给定目的；第二，除了给定目的外，切勿使用通用名称；第三，确保目的足够狭窄，以使所有具有名称的变量都具有相同的行为。在本章开头的文件系统错误中违反了此第三项要求。文件系统使用块来表示具有两种不同行为的变量（文件块和磁盘块）；这导致对变量含义的错误假设，进而导致错误。

Sometimes you will need multiple variables that refer to the same general sort of thing. For example, a method that copies file data will need two block numbers, one for the source and one for the destination. When this happens, use the common name for each variable but add a distinguishing prefix, such as srcFileBlock and dstFileBlock.

有时您将需要多个变量来引用相同的一般事物。例如，一种复制文件数据的方法将需要两个块号，一个为源，一个为目标。发生这种情况时，请对每个变量使用通用名称，但要添加一个可区分的前缀，例如 srcFileBlock 和 dstFileBlock。

Loops are another area where consistent naming can help. If you use names such as i and j for loop variables, always use i in outermost loops and j for nested loops. This allows readers to make instant (safe) assumptions about what’s happening in the code when they see a given name.

循环是一致性命名可以提供帮助的另一个领域。如果将诸如 i 和 j 之类的名称用于循环变量，则始终在最外层循环中使用 i，而在嵌套循环中始终使用 j。这使读者可以在看到给定名称时对代码中发生的事情做出即时（安全）假设。