Best method for storing and calling function as variable?

CantSayIHave

I just created a Button class for my current project, and I'd like a way to assign a function to each button created.

It would be most useful to store the function as a variable upon calling the constructor and later call that function when a click is detected inside the Button. After searching the forums I see it's rather difficult to do this, and it's also a bad idea to store the function name as a String and use that to call it.

I'd like to avoid hard coding the functions for each button into a clickHandler function. Do you guys have suggestions on what to do?

Thanks

GoToLoop

https://forum.Processing.org/two/discussion/14039/button-problem-method

CantSayIHave

This is clever, thanks

CantSayIHave

Quick question, in your solution, why is it necessary for action() to be abstract? Can you only override abstract methods?

GoToLoop

• Keyword abstract is just something fancy which obliges us to implement all methods marked as such when we try to instantiate or extend its class.
• An abstract class is an incomplete class. That is, it can have incomplete abstract methods.
• It's a mix between interfaces & classes. BtW, all methods in an interface are implicitly abstract.
• For example we coulda replaced abstract void action(); w/ void action() {}.
• But then any1 trying to instantiate that class would fail to realize that method action() isn't complete and needs to be implemented w/ something other than empty.
• As an experiment, try to instantiate Button w/ just a regular new Button() like:
  btns[0] = new Button(GAP, y, BTN_W, BTN_H, #FF0000) {};
• It'll fail to compile b/c action() "must" be implemented.
• Also b/c abstract classes can't be instantiated w/ just new.
• Now remove the abstract mark from action(): void action() {}
• It will compile w/o dealing w/ action(). But then action() won't do anything. :P

P.S.: Notice that in order to directly instantiate an abstract class we need to at least add {};
after new like new Button() {};.

However do not add {}; for regular classes. It ends up instantiating them as if they were some derived class for no reason or gain:

1. new PVector() {}; // WRONG! Derived class object.
2. new PVector(); // RIGHT! Real PVector object.

CantSayIHave

This is incredibly helpful, thanks so much!