As I mentioned above, I think there may be some other issues with your game/code.
If you are creating multiple enemies and are not careful about how you use globals, you will get into problems.
However, there is an easy way to be sure your code works (once you understand the syntax).
Here is a suggested change (with some additions; #'d comments explained after code):
local function createEnemy() -- #1
local curEnemy -- #2
-- Add your own code to make an enemy object here
-- Be sure to store a reference to the enemy in curEnemy local created above
-- Now, attach a set of functions and methods to your enemy like this:
curEnemy.shoot = function() -- #3
local thisEnemy = curEnemy -- #4
if(thisEnemy == 100) then
ball = display.newImage("images/ball.png");
ball.x, ball.y = thisEnemy.x, thisEnemy.y;
transition.to(ball, {x = hero.x, y = hero.y});
end
end
function curEnemy:moveToHero() -- #5
self.myTransition = transition.to(self, {time = 2000, x=100, y=display.contentCenterY + 50, onComplete = self.shoot});
end
function curEnemy:destroy() -- #6
if( self.myTransition ) then
transition.cancel( self.myTransition )
end
self:removeSelf()
end
return curEnemy - #7
end
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It is usually better to have a ‘builder’ function and to call a builder when you need it rather than embed building code in other logic. This makes builder code easy to maintain and supplement.
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The first thing to do is to make a local variable to contain your new build object (the enemy). This makes it easy to modify and to attach functions/methods to.
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This is a function attached to the current enemy we are making. You call the function like this: var.shoot() , where var is a variable containg a reference to the enemy object. (See more code examples below.)
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When the shoot() function is being defined, we store a copy of the curEnemy reference in a local variable within the new function. Every time a new enemy is created, the code to create the shoot() function is executed and every enemy gets its own shoot function with a unique refernce to that enemy inside it. We have to do this, because when you call a function attached to an object, the function doesn’t know what object its parent is. Furthermore, the callback part of transition only takes functions not methods. i.e. We will give the callback reference enemy.shoot(), but it won’t know which one. Storing a refernce inside the function when we write/generate it solves this connundrum. Note: This is a bit redundant in that I could simply have refered to ‘curEnemy’ in all of the shoot() function, but I like to use a local reference for clarity sake.
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moveHero() is a method call. Later we can call it like this: var:moveToHero() , where var is a variable containg a reference to the enemy object. When we do this, moveHero is automatically passed a variable ‘self’ containing a reference to the enemy object stored in var.
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Here we add a method named destroy(). It contains code to cancel any oustanding transtion and then remove the enemy object from the scene.
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Lastly, we return ‘curEnemy’ from our builder function. (See below to understand how this call comes together.)
Now, we can use our builder and its attached methods to do some work:
local myEnemy = createEnemy()
myEnemy:moveToHero()
.... Later, we can destroy this enemy (as long as we have kept track of the object ID in 'myEnemy' somehow.):
myEnemy:destroy()
I hope this is helpful and not confusing. Please note: In the future I will be putting together tutorials on game making and mechanics. So if you are interested, keep track of my RSS feed or visit my site occasionally.
Cheers,
Ed
Roaming Gamer, LLC.
SSK for Corona SDK (github) (videos)
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