Max says…

My work has recently taken a departure from the usual web development as I’ve been “borrowed” by the other development team to help out with a Java project. Now, my Java is reasonable sound but yesterday I came across a curious situation involving passing about the current object.

In common with a lot of languages, the current object is represented by the ‘this’ keyword. I wanted to pass ‘this’ to a static method of another class. Of course, I can’t refer to the object as ‘this’ in the static method context as that would be ambiguous insofar as it could refer to the class with the static method I’m working with. This pattern is often used with callbacks where for example you might want to register a class with a particular listener objcet. To avoid confusion, I named the actual parameter in the static method

that

I assumed that I would reference the fields and methods of the object using

that.someMethod()

rather than

this.someMethod()

This is where the fun begins. Let’s call the original object

SomeObject theObject

and I want to call the static method

SomeClass.doStaticMethod(SomeObject that)

I would call that method, from within theObject, using

SomeClass.doStaticMethod(this)

When in theObject, I have access to private fields and methods since private fields and methods are within scope. I assumed the same would be true when I passed “theObject” as “this” to “SomeClass.doStaticMethod(SomeObject that)”. However, when I actually try to access private fields such as “that.privateField”, it would appear that I no longer have access. I could create appropriate accessor methods, but that would defeat the idea of encapsulation.

Does anyone have any ideas? Am I missing some fundamental (and so obvious I missed it) rule of scope or object passing?