条款23：宁以non-member、non-friend替换member函数

主要原因：non-member、non-friend带来的封装性比member函数高。

 

例如C++的做法：结合了namespace

/ header "webbrowser.h" - header for class WebBrowser itself // as well as "core" WebBrowser-related functionality namespace WebBrowserStuff { class WebBrowser { ... }; ... // "core" related functionality, e.g. // non-member functions almost // all clients need } // header "webbrowserbookmarks.h" namespace WebBrowserStuff { ... // bookmark-related convenience } // functions // header "webbrowsercookies.h" namespace WebBrowserStuff { ... // cookie-related convenience } // functions ...