Java Question Wrapping many sub-classes of same super class

warwound

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Longtime User
I'm looking for a quick/elegant way to wrap a super class and many different sub-classes that all extend the same super class.

Say i have a class MySuper and i have already wrapped that class using AbsObjectWrapper:

B4X: 
public class MySuperWrapper extends AbsObjectWrapper<MySuper> {
  public void Initialize(){
    setObject(new MySuper());
  }

  public void DoSomething(){
    getObject().doSomething();
  }
}

Now i have 6 or 7 other classes that extend MySuper class, each of these 6 or 7 other classes add various methods and properties to MySuper.
MySuper already has many methods and properties.

So a 'brute force' solution is to wrap each sub-class of MySuper and duplicate the code that wraps all methods and properties of MySuper:

B4X: 
public class SubClass1Wrapper extends AbsObjectWrapper<SubClass1> {
  public void Initialize(){
    setObject(new SubClass1());
  }

  public void DoSomething(){
    getObject().doSomething();
  }

  public void NewMethod(){
    getObject().newMethod();
  }
}
B4X: 
public class SubClass2Wrapper extends AbsObjectWrapper<SubClass2> {
  public void Initialize(){
    setObject(new SubClass2());
  }

  public void DoSomething(){
    getObject().doSomething();
  }

  public void AnotherNewMethod(){
    getObject().anotherNewMethod();
  }
}

Do-able but there must be a better and more elegant solution?

I was reading this recent thread: http://www.b4x.com/forum/bugs-wishl...d-feature-toggle-button-click.html#post152489.
Is there a solution that uses generics and parameterized classes?
(These are java concepts i have yet to deal with in any depth).

Could i wrap the super class and then re-use that wrapped class when wrapping the sub-classes and avoid lots of duplicate code?
If the java library and these classes i am wrapping gets updated then maintenance of the b4a library will be a pain in the a#se unless i can find the solution i am looking for.

Thanks.

Martin.
 

agraham

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warwound

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Licensed User
Longtime User
Thanks for the reply - it's your post in the thread you linked to that i also linked to in my post.

I think what i was asking for was an example of how to use generics with AbsObjectWrapper...
So i did some experiments and found an answer:

B4X: 
public class MySuperWrapper<T extends MySuper> extends AbsObjectWrapper<T> {
  public void Initialize(){
    setObject(new MySuper());
  }

  public void DoSomething(){
    getObject().doSomething();
  }
}

B4X: 
public class SubClass1Wrapper<T extends MySuper> extends MySuperWrapper<T> {
  public void Initialize(){
    setObject(new SubClass1());
  }

  public void NewMethod(){
    getObject().newMethod();
  }
}

B4X: 
public class SubClass2Wrapper<T extends MySuper> extends MySuperWrapper<T> {
  public void Initialize(){
    setObject(new SubClass2());
  }

  public void AnotherNewMethod(){
    getObject().anotherNewMethod();
  }
}

Eclipse now complains The method setObject(T) in the type AbsObjectWrapper<T> is not applicable for the arguments (SubClass1) (that refers to SubClass1Wrapper).
It suggests to cast the new instance of SubClass1 to T and then everything compiles ok.

Martin.
 

warwound

Expert
Licensed User
Longtime User
I was simple trying to find a way to include the 'already wrapped and commented' parts of the super class in the yet to be wrapped sub classes.
Not sure if that requires generics or not...

BUT i found a better solution.
I looked through all of these classes and they contain no methods or properties - just a lot of fields (instance members) - they are data structures for various types of eeproms.
Previously i planned to write a lot of getter and setter methods to access the fields of the wrapped object.
The fields are all public so i've now simply created a new simple class that extends the class i was originally going to wrap with AbsObjectWrapper:

B4X: 
@ShortName("MySuper")
public class MySuper extends third.party.package.name.MySuper{
  // the body of this new class is empty
}

I've done the same for the sub classes of the super class.

Quick n simple!
The library compiles and in the b4a IDE auto-complete list all fields from the super and sub classes appear as expected.

The only thing it lacks is documentation/reference for the fields in the IDE, if that is essential then i will manually add it to the library XML file once the library is complete - though that will itself be a maintenance headache if i need to recompile the library.

Erel has said before that using AbsObjectWrapper is not always the the best choice he's right!

Martin.
 
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