Before I post too many SOLID principle posts, let me prefix by saying that I strongly believing that following SOLID principles as guidelines will lead to writing better Object Oriented code.
Back to Open/Close Principle…
Software entities like classes, modules and functions should be open for extension but closed for modifications.
Out of all the SOLID principles, I’ve found this one to causes the most confusion and is the hardest to identify for developers. When following any of the SOLID principles, they all have a bit of cross over that help you identify when violating one of them. Violating Open/Close principle usually means you are also violating Single Responsibility.
Here are a few smells/tips to for identifying when you might be violating Open/Closed principle:
- Conditional Code
- Multiple unit tests due to multiple execution paths
- Violation of Single Responsibility
public int GetSpeed()
int speed = 0;
if (_type is Bike)
speed = 10;
else if (_type is Car)
speed = 70;
else if (_type is Jet)
speed = 300;