CS 372 Spring 2016  >  Notes for February 17, 2016

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CS 372 Spring 2016
Notes
for February 17, 2016

The following is an outline of the February 17 lecture.

Clean Code (cont’d)

Functions [CC chapter 3]

We touched briefly on just one topic from this chapter.

• Command-Query Separation
  • A command is a function that performs an action. A query is a function that answers a question. Keep the two kinds of functions distinct.
  • This is an expression of the generalized Single Responsibility Principle (SRP): that a software module should have only one well defined responsibility.
  • The distinction often (but not always) corresponds to the distinction between non-const and const member functions in a C++ class.
    • Const member functions generally provide information via a return value.
    • Non-const member functions generally have void return type.
  • Command-query separation can help with:
    • Making an API easy to understand.
    • Error handling. It is expressed in the C++ rule (which you really do not want to break) that a non-const member function should not return an object by value.

Clean Code will be continued next time.