api設计原则.docVIP

API Design Principles One of Qt’s most reputed merits is its consistent, easy-to-learn, powerful API. This document tries to summarize the know-how we’ve accumulated on designing Qt-style APIs. Many of the guidelines are universal; others are more conventional, and we follow them primarily for consistency with existing APIs. Although these guidelines are aimed primarily at public APIs, you are encouraged to use the same techniques when designing internal APIs, as a courtesy to your fellow developers. You may also be interested to read Jasmin Blanchette’s Little Manual of API Design [chaos.troll.no] Six Characteristics of Good APIs An API is to the programmer what a GUI is to the end-user. The ‘P’ in API stands for “Programmer”, not “Program”, to highlight the fact that APIs are used by programmers, who are humans. In his Qt Quarterly 13 article about API design [], Matthias tells us he believes that APIs should be minimal and complete, have clear and simple semantics, be intuitive, be easy to memorize, and lead to readable code. Be minimal: A minimal API is one that has as few public members per class and as few classes as possible. This makes it easier to understand, remember, debug, and change the API. Be complete: A complete API means the expected functionality should be there. This can conflict with keeping it minimal. Also, if a member function is in the wrong class, many potential users of the function won’t find it. Have clear and simple semantics: As with other design work, you should apply the principle of least surprise. Make common tasks easy. Rare tasks should be possible but not the focus. Solve the specific problem; don’t make the solution overly general when this is not needed. (For example, QMimeSourceFactory in Qt 3 could have been called QImageLoader and have a different API.) Be intuitive: As with anything else on a computer, an API should be intuitive. Different experience and background leads to different perceptions on what is intuitive and w