Software Development Cross Solution - Index of - Free

don’t repeat yourself
Your design should obey the SRP, but also be DRY...
The SRP is all about responsibility, and which objects in your system do what.
You want each object that you design to have just one responsibility to
focus on—and when something about that responsibility changes, you’ll know
exactly where to look to make those changes in your code. Most importantly
you’ll avoid what’s called the ripple effect, where one small change to your
software can cause a ripple of changes throughout your code.
But there’s a principle that goes hand in hand with SRP, and that’s DRY:
160 Chapter 5
Don’t repeat yourself
Avoid duplicate code by abstracting or
separating out things that are common and
placing those things in a single location.
The different Date classes are not DRY
Each of the different Date classes (FirstDate, SecondDate, ThirdDate)
have almost identical behavior in their validateEvent() methods. This not
only breaks the SRP, but means that one change in logic—like specifying that you
can actually Sleep Over on the second date—would result in changes to the logic
in all three classes.
FirstDate
# validateEvent(event : Event)
:boolean
SecondDate
# validateEvent(event : Event)
:boolean
These methods have nearly
identical code......but this should be a single behavior, not
three separate pieces of functionality.
ThirdDate
# validateEvent(event : Event)
:boolean
This quickly turns into a
maintenance nightmare.
DRY is about having each piece of
information and behavior in your
system in a single, sensible place.
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