Open closed prinicple, problem
- by Marcus
Hi,
I'm trying to apply OCP to a code snippet I have that in it's current state is really smelly, but I feel I'm not getting all the way to the end.
Current code:
public abstract class SomeObject
{}
public class SpecificObject1 : SomeObject
{}
public class SpecificObject2 : SomeObject
{}
// Smelly code
public class Model
{
public void Store(SomeObject someObject)
{
if (someObject is SpecificObject1)
{}
else if (someObject is SpecificObject2)
{}
}
}
That is really ugly, my new approach looks like this:
// No so smelly code
public class Model
{
public void Store(SomeObject someObject)
{
throw new Expception("Not allowed!");
}
public void Store(SpecificObject1 someObject)
{}
public void Store(SpecificObject2 someObject)
{}
}
When a new SomeObject type comes along I must implement how that specific object
is stored, this will break OCP cause I need to alter the Model-class.
To move the store logic to SomeObject also feels wrong cause then I will violate SRP (?), becuase in this case the SomeObject is almost like a DTO, it's resposibility it not how to know to store itself.
If a new implementation to SomeObject comes along who's store implementation is missing
I will get a runtime error due to exception in Store method in Model class, it also feels like a code smell.
This is because calling code will in the form of
IEnumerable<SomeObject> sequence;
I will not know the specific types of the sequence objects.
I can't seem to grasp the OCP-concept. Anyone has any concrete examples or links that is a bit more than just some Car/Fruit example?
