As stated in the Help Center, one of the criteria for a question to be on topic is:

• Is it actual code from a project rather than pseudo-code or hypothetical code?
  
  Details matter! In order to give good advice, we need to see real, concrete code, and understand the context in which the code is used. Generic code (such as code containing placeholders like foo, MyClass, or doSomething()) leaves too much to the imagination.

What is the rationale for that rule?