NR.4: Don't insist on placing each class declaration in its own source file
NR.4：不要坚持将每个类声明放在其自己的源文件中
Reason（原因）
The resulting number of files from placing each class in its own file are hard to manage and can slow down compilation. Individual classes are rarely a good logical unit of maintenance and distribution.
将每个类放在自己的文件中而产生的文件数量很难管理，并且可能减慢编译速度。单个类很少是维护和分发的良好逻辑单元。
Example（示例）
代码语言：javascript复制???
Alternative（代替选项）
- Use namespaces containing logically cohesive sets of classes and functions. 使用包含逻辑上紧密结合的类和函数组合的命名空间。
原文链接
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#nr4-dont-insist-on-placing-each-class-declaration-in-its-own-source-file
