notes on "Clean Code - Functions" chapter

Main thoughts I want to remember from that chapter:

• Functions should be small. Small means up to several lines.
• Functions should have descriptive names.
• Functions should do one thing. They should do it well. They should do it only. THis means that the side effects should be as limited as possible (preferably - there should be none).

• It should be possible to read the function as a “To …” sentence:

  TO functionName we do something and then we do something else...
  

• Functions should operate on a single level of abstraction.
• switch statements should be avoided. They can probably get replaced by inheritance - if not should be hidden in a single place in such way that it won’t be necessary to create similar switch statements again.
• The smaller the number of arguments == the better. Rule of thumb: three parameters is almost always too much. One and two parametrs is acceptable.
• Don’t use arguments as a way to communicate with outer world - don’t use output parameters.
• Throw exceptions instead of returning error codes. You don’t enforce handling the error right away - it can be dealt with in a convenient place in code.

Remember: functions are not written correctly at first. Write something meeting functional requirements with TDD and then refactor mercilessly.