alice-teacher Global Variables

[Don Slater]

See the attached screen shot and Alice world (countClicks.a2w)

I have created a project with a t_rex and a triceratops, and I want to count when each is clicked on. I have created a variable for the t-rex and triceratops that keeps track of the number of times each is clicked on.

I have written a world method countClicks with an object parameter objectsClicked (shown in the screen shot).

IN the events editor, I have created a "when the mouse is clicked on anything do” event. I leave <anything> as the possible target to trigger the event, and from the do: drop down menu, I select the world countClicks method and from the objectClicked parameter menu, I select “expressions” and “object under mouse cursor”.

I hope that this answers your question (I hope that I understood your question! ;-) )

Please let me know if I have misunderstood, or if you have any other questions.

All the best,
Don Slater






On Dec 11, 2013, at 11:11 AM, Emily Higgins <erphiggins at gmail.com> wrote:

> I can see how to pass a variable between the methods, but how can I pass it between an event listener and a method?  I want to, for example, keep track of number of mouse clicks during a game.  How can I do that?  I can't create a parameter in an event listener....  I think I am missing a step or a piece of understanding in figuring out how to manage this.
> 
> Thank you
> Emily Higgins
> Boothbay Region High School
> Boothbay, Maine
> 
> 
> On Wed, Dec 11, 2013 at 1:17 PM, Don Slater <dslater at andrew.cmu.edu> wrote:
> Alice 3 does not really support global variables in the same way as Alice 2. Alice 3 is Java-based, with a strong sense of scope for variables.
> 
> It is possible to create a variable that belongs to the Scene class, that can be used by any other methods (functions and procedures) written on the Scene class. But If I am writing a method for the Penguin class, that method does not have access to the variable created in the Scene. That Scene variable must be passed as a parameter to the Penguin method that would like to use it, and a function of the Penguin class must return a value to for updating the Scene variable.
> 
> Please let me know if you have any other questions.
> 
> Later,
> Don Slater
> 
> On Dec 10, 2013, at 3:04 PM, Robert Durtschi <robert.durtschi at gcsu.edu> wrote:
> 
> > I'm guessing it's the same for Alice 3; In Alice 2.x variables created as properties of the World object (top object in the object-tree) could be seen/manipulated by all other objects.
> >
> >
> > Hello All -
> > I am trying to iterate a counter in an event listener, so that if the user
> > clicks on four objects, an action occurs.   How can I do this?  I also
> > can't figure out how to make a global variable that can be accessed
> > throughout the program.
> >
> > Emily Higgins
> > Boothbay Region High School
> > Boothbay Harbor, Maine
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