Coupling of objects
Assuming I have methods of doA(), doB() and doC() of classes A,B and C respectively.
Than unless I am wrong, doA() method should belong to class A. It must be executed from Class A. If a method doA() that does the responsibilities for A, exists in Class B. than 开发者_开发百科class A is coupled to B's services. This also represents low cohesion, and high coupling
is my reasoning correct?
A class has maximum cohesion if all its methods operate on all it's member variables.
public class MyClass
{
private int value1;
private int value2;
private int value3;
public int Method1()
{
return value1 + value2;
}
public int Method2()
{
return value1 - value2;
}
// doesn't belong on this class
public int Method3()
{
return value3 * 2;
}
}
Coupling comes in two forms:
- A class uses another class internally. This is coupling but is kind of okay in that it's an example of composition over inheritance
Example:
public class MyClass
{
public void Method1()
{
var c = new MyOtherClass();
c.DoSomething();
}
}
- Worse coupling looks like this and is often referred to as a Law of Demeter violation.
Example:
public class MyClass
{
public void Method1()
{
var c = new MyOtherClass();
var size = c.Members.Size;
...
}
}
In this case, MyClass
is coupled not only to MyOtherClass
, but the structure of MyOtherClass
and this is where you get into trouble and your code gets rigid and fragile.
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