Oleg Andreev

Don’t tie external resources lifetime to object lifetime (for instance, file descriptors). Never start any process in constructor/initializer. Have “start” and “stop” methods (or “open”/“close”) dedicated for managing the resource.

Don’t mix data construction and performing a procedure. Whenever you have a method which takes 10 arguments, it is time to create a separate object just for that procedure. Give it 10 properties and a “start” method. Later you’ll be able to add more configuration options and alternative invocation APIs to this object in a clean way.

In general, when you begin understanding OOP, you tend to treat everything as an object. Data structure, complex procedure, network connection, physical device — all become objects. The trick is while you incapsulate all those things into objects, you shouldn’t confuse the *object* with the *thing* it manages. The object is a manager, driver for the thing, but not the thing itself. Object may have language-oriented API and thing-oriented API. Don’t mix them. First API lets you to create, initialize, inspect, destroy object. It must have no impact on the thing. To manipulate the thing, you write thing-specific methods.

Quick test for compliance: you should be able to instantiate a valid object, set properties in any order, inspect it and destroy without any effect on other objects and things around.