Greenfoot

ggongwer

2016/5/8

#

Hello, I am trying to use the intersects(Actor other) method in an Actor in a World, but keep getting the message intersects(Greenfoot.Actor) has protected access in Greenfoot.Actor I am using it in a subclass of Actor, and I thought that was okay for a protected method. Am I misunderstanding "protected"?

ggongwer

2016/5/8

#

Never mind, Greenfoot friends. I figured it out :)

danpost

2016/5/9

#

ggongwer wrote...

Never mind, Greenfoot friends. I figured it out :)

To clarify, 'protected' means you can only explicitly call the method on 'this'. That is,

// valid are
if (this.interects(someActor)) // explicit object
// and
if (interects(someActor)) // implicit object (still 'this')
// and this may even work
Actor thisActor = this;
if (thisActor.intersects(someActor))

// invalid are
if (someOtherActor.intersects(someActor))
// and
if (someOtherActor.intersects(this))

ggongwer

2016/5/10

#

Thanks, DanPost!

danpost

2016/5/10

#

danpost wrote...

To clarify, 'protected' means you can only explicitly call the method on 'this'.

I guess this is not entirely accurate. You can call a protected method on any object that is created from that particular class or a subclass of it. So, if you call the 'intersects' method from a class called 'SomeActor', then it must be called on an object of type SomeActor:

// valid in SomeActor class
Object object = getWorld().getObjects(SomeActor.class).get(0); // assume at least one is in the world
SomeActor someActor = (SomeActor)object;
boolean touchesSomeOtherActor = someActor.intersects(SomeOtherActor.class);

// using this for the last line will not compile even though the object is a SomeActor object
boolean touchesSomeOtherActor = object.intersects(SomeOtherActor.class);

ggongwer

2016/5/11

#

Thanks for clarifying. I was trying to call it from a sibling class, and that's what generated the error.

Activity

About

Documentation

Download

Discuss

Scenarios

Error trying to use "intersects"