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Director
How to Build a Timer Object Using Lingo
Perhaps you're experimenting with object oriented programming for the first time, or maybe you're experienced in another language in just need an example of how to do it in Lingo. Either way, the following tutorial should prove useful for demonstrating how to create and use an object with Lingo and why it can be very useful. If you have something to contribute [or contest], please post your comments to the forums.

Check out the source movie with this example to get an even closer look at the timer object. Good luck!

Download the FREE Director source movie here! [Director 8.0, 77Kb]

Why use objects?
Imagine a Director project you've created and you've made a car that you can make move around the screen and basically make behave like a car. Perhaps you've created global variables that remember certain attributes about your car such as how much gas it has, what gear it's in, it's velocity, direction, etc. Your car works perfectly fine, but there is still a problem. What if you need 10 cars moving around the screen instead of 1? This is where objects come into the picture. Instead of storing one set of global variables to remember all the attributes of one car, you create a car object that remembers these attributes for you. In addition to these attributes, your car object also handles functions such as shifting your car into different gears, accelerating, braking, and reporting fuel usage, among many other things. The real beauty of the situation is that you can create as many instances of this car object as you like. So, having 10 cars on your screen, remembering how much gas each one has, what speed each one is traveling, and what direction each one is going, is no longer a problem. In fact, you could have ANY number of cars all doing different things and it would still be easy for you to manage.

The Timer Object example
The following timer object demonstrates the use of objects by showing how "the timer" in Director can be used to represent an infinite number of independent timers.

First of all, start "the timer" in your startMovie:

on startMovie
    startTimer
end


Next, put the following code into a cast member all by itself and give that member a name. If you name the member "timerObject", then that is the name you'll use when creating an instance of the timer later on.

property startedTime, additionalTime, isStarted

on new me
    set additionalTime = 0
    set startedTime = 0
    set isStarted = FALSE
    return me
end

on ActivateTimer me
    set the startedTime of me = the timer
    set the isStarted of me = TRUE
end

on ReportTimer me
    if (the isStarted of me = TRUE) then
       return integer((the timer - startedTime) + additionalTime)
    else
       return 0
   end if
end

on AddToTimer me, addTime
    set the additionalTime of me = the additionalTime of me + addTime
end

on DeactivateTimer me
    set the isStarted of me = FALSE
    set the additionalTime of me = 0
    set the startedTime of me = 0
end


The first thing you see in the code is a list of properties. These are attributes that will be remembered by your object. After the properties, there are 5 handlers. These handlers provide the functionality of your object. The "on new me" handler is special and required in all object scripts. Every time you create a new instance of an object, this special handler will be called and it is the handler that returns the object instance when creating a new object. The "return me" line of this handler will be present in every object script. Now, let's create an instance of this object:

on mouseUp
    global gTimer1

       set gTimer1 = new(script "timerObject")
end


gTimer1 is now a timer object instance and since we made it a global variable, it can be accessed anywhere in your program. Imagine a button that toggles between stopping and starting a timer. Here is an example:

on mouseUp
   global gTimer1

       if the isStarted of gTimer1 = FALSE then
          ActivateTimer(gTimer1)
       else
          put "It's been "&ReportTimer(gTimer1)&" timer ticks since you started."
          DeactivateTimer(gTimer1)
       end if
end

Now go get the source file and try it yourself!

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