Variables inside Functions (Corona Lua) - lua

I've searched everywhere for an answer on how to change a variable inside a function. I have tried many different solutions but none have worked so far.
My plan is to change a variable named 'stateRed' inside a function which is run when a button is pressed. When the function is run, the variables will change to 'READY'. I will then use this variable to run a separate chunk of code (the actual game). There are two of these buttons.
My code looks something like this:
function ReadyRed()
stateRed = 'READY'
stateBtnRed = widget.newButton
{
defaultFile = "ready_red.png",
overFile = "unready_red.png",
label = "Ready",
emboss = true,
onPress = unreadyStateRed,
}
stateBtnRed.rotation = 90; stateBtnRed.width = 90; stateBtnRed.height = 90; stateBtnRed.x = display.contentWidth / 2 - 170; stateBtnRed.y = display.contentHeight - 270
return stateRed
end
function UnreadyRed()
local stateRed = 'UNREADY'
stateBtnRed = widget.newButton
{
defaultFile = "unready_red.png",
overFile = "ready_red.png",
label = "Unready",
emboss = true,
onPress = readyStateRed,
}
stateBtnRed.rotation = 90; stateBtnRed.width = 90; stateBtnRed.height = 90; stateBtnRed.x = display.contentWidth / 2 - 170; stateBtnRed.y = display.contentHeight - 270
return stateRed
end
The code that starts the game looks like this:
if stateRed == 'READY' and stateBlue == 'Ready' then

If variable stateRed is global then remove local keyword stand before variable name i.e.
function UnreadyRed()
stateRed = 'UNREADY'
...
end
Note:
You probably don't need return stateRed in ReadyRed and UnreadyRed functions since stateRed is global variable.
Use one notation style. I recommended you Camel Case notation

Related

main.lua:25:attempt to call method'setanchorPoint'(a nil value)stack traceback:main.lua25:in maiin chunk

I am geeting an error: main.lua:25:attempt to call method'setanchorPoint'(a nil value)stack traceback:main.lua25:in maiin chunk. Please tell me how can I use anchorPoint. And how to resolve this issue
--constants
_H = display.contentHeight;
_W = display.contentWidth;
mRand = math.random;
o = 0;
time_remain = 10;
time_up = false;
total_orbs = 20;
ready = false;
--Prepare sounds to be played or accessed
local soundtrack = audio.loadStream("media/soundtrack.caf");
local pop_sound = audio.loadSound("media/pop.caf");
local win_sound = audio.loadSound("media/win.caf");
local fail_sound = audio.loadSound("media/fail.caf");
local display_txt = display.newText("Wait", 0, 0, native.systemFont, 16*2);
display_txt.xScale = .5; display_txt.yScale = .5;
display_txt:setanchorPoint(display.BottomLeftanchorPoint);
display_txt.x = 20; display_txt.y = _H-20;
If you want to know how to use anchor points in Corona, the usual approach is to refer to the Corona manual....
Corona Anchor Guide
Anchors
The anchor of an object controls how geometry is positioned
relative to the object's origin. This is specified via the
object.anchorX and object.anchorY properties.
They even give examples....
You cannot just invent function names and wonder why you get error messages for callinig them.

for loop help and sprite addition

I have two questions. what I am
trying to do is every time I shoot a enemy/vine it should be
removed and a explosion should occur. the removal works perfect
but the sprite is not called to explode
What's this in the for loop #sections[sectInt]["vines"] ?
Are they parent/ child references? Can someone break this
down to the letter even telling me what the # is?
How can I use my explosion sprite after each vine is destroyed?
I am having a difficult time figuring out how to call every x and y
vine in the for loop to explode when removed.
Code:
local sections = require("sectionData")
local lastSection = 0
function createSection()
--Create a random number. If its eqaul to the last one, random it again.
local sectInt = mR(1,#sections)
if sectInt == lastSection then sectInt = mR(1,#sections) end
lastSection = sectInt
--Get a random section from the sectionData file and then
--Loop through creating everything with the right properties.
local i
-- the random creation of vines throughout the screen
for i=1, #sections[sectInt]["vines"] do
local object = sections[sectInt]["vines"][i]
local vine = display.newImageRect(objectGroup, "images/vine"..object["type"]..".png", object["widthHeight"][1], object["widthHeight"][2])
vine.x = object["position"][1]+(480*object["screen"]); vine.y = object["position"][2]; vine.name = "vine"
local rad = (vine.width*0.5)-8; local height = (vine.height*0.5)-8
local physicsShape = { -rad, -height, rad, -height, rad, height, -rad, height }
physics.addBody( vine, "static", { isSensor = true, shape = physicsShape } )
end
end
-- explosion sprite
options1 =
{
width = 96, height = 96,
numFrames = 16,
sheetContentWidth = 480,
sheetContentHeight = 384
}
playerSheet1 = graphics.newImageSheet( "images/explosion.png", options1)
playerSprite1 = {
{name="explosion", start=1, count=16, time = 400, loopCount = 1 },
}
explode = display.newSprite(playerSheet1, playerSprite1)
explode.anchorX = 0.5
explode.anchorY = 1
--player:setReferencePoint(display.BottomCenterReferencePoint)
-- i want to reference the for loop position if each vine so it plays sprite when they are removed
explode.x = "vine.x" ; explode.y = "vine .y"
explode.name = "explode"
explode.position=1
extraGroup:insert(explode)
1) What's this in the for loop #sections[sectInt]["vines"] ? Are they parent/ child references? Can someone break this down to the letter even telling me what the # is?
As I said in my comment the # is table length.
The loop is looping over each bit of "vine" data in the selected segment data (whatever that means exactly in terms of the game) and then creates the objects for those vines.
When it's time to make your vine explode, you play the sprite. If you want to explode every vine, you would have something like:
sheetOptions =
{
width = 96, height = 96,
numFrames = 16,
sheetContentWidth = 480,
sheetContentHeight = 384
}
playerSheet = graphics.newImageSheet( "images/explosion.png", sheetOptions)
spriteSequence = {
{name="explosion", start=1, count=16, time = 400, loopCount = 1 },
}
for i, vine in ipairs(objectGroup) do
local explode = display.newSprite(playerSheet, spriteSequence)
explode.anchorX = 0.5
explode.anchorY = 1
explode.x = vine.x
explode.y = vine.y
explode.name = "explode"
explode.position=1
explode:play()
extraGroup:insert(explode)
end
Note: not tested, let me know of if any issues you can't resolve.
ok so, this is what i did to get my object to have a explosion, for anybody that is having the same issue.
function isShot( event )
print('shot!!!')
if (event.other.class == "enemy") then
if (event.other.name == "limitLine") then
event.target:doRemove() --remove bullet if hits the limitLine
elseif (event.other.name == "vine") then
event.other:doRemove()
spriteExplode(event.other.x, event.other.y) -- this function calls itself & runs the sprite
if event.other.name == "vine" then
if event.other.name == "explode" then
event.other:doRemove() --this removes the explosion sprite
end
end
end
-- remove the bullet & explosion sprite
timer.performWithDelay( 5000, function(event) explode:doRemove(); end, 1 )
event.target:doRemove()
end
return true
end
function spriteExplode( x, y)
explode.isVisible = true
explode:play()
print("play explode")
if (x and y) then -- this is the code that keeps my sprite updating upon removal of vine
explode.x, explode.y = x, y
end
function explode:doRemove(event)
timer.performWithDelay(
1,
function(event)
display.remove(self)
self= nil
end,
1 )
end
end
i added the isShot function eventListener inside of the Bullet function
bullet:addEventListener("collision", isShot) & a bullet:doRemove function is inside the bullet function as well.
hope this helps.

Corona SDK(LUA) - attempt to call upvalue 'spawnEnemy'(a nil value)

I just trying to add eventListener to a object, which should disappear when I tap on it. But I get error mentioned in the title. Here is my whole code at this point :
-- housekeeping stuff
display.setStatusBar(display.HiddenStatusBar)
local centerX = display.contentCenterX
local centerY = display.contentCenterY
-- set up forward references
local spawnEnemy
-- preload audio
-- create play screens
local function createPlayScreen()
local bg = display.newImage("background.png")
bg.y = 130
bg.x = 100
bg.alpha = 0
local planet = display.newImage("planet.png")
planet.x = centerX
planet.y = display.contentHeight +60
planet.alpha = 0
transition.to( bg, { time = 2000, alpha = 1, y = centerY, x = centerX } )
local function showTitle()
local gametitle = display.newImage("gametitle.png")
gametitle.alpha = 0
gametitle:scale (4, 4)
transition.to( gametitle, { time = 500, alpha = 1, xScale = 1, yScale = 1 })
spawnEnemy()
end
transition.to( planet, { time = 2000, alpha = 1, y = centerY, onComplete = showTitle } )
end
-- game functions
local function shipSmash(event)
local obj = event.target
display.remove( obj )
end
local function spawnEnemy()
local enemy = display.newImage("beetleship.png")
enemy.x = math.random(20, display.contentWidth - 20)
enemy.y = math.random(20, display.contentHeight - 20)
enemy:addEventListener ( "tap", shipSmash )
end
local function startGame()
end
local function planetDamage()
end
local function hitPlanet(obj)
end
createPlayScreen()
startGame()
And here is how error window looks like :
I'm kinda new in this area(LUA programming) so sorry for maybe dumb syntax error or something, but what I saw is that this error shows up after I write this line of code: enemy:addEventListener ( "tap", shipSmash )
Change local function spawnEnemy() to function spawnEnemy() as this variable was already declared earlier. Yes, this is typical Lua pitfall for beginners.
You've declared spawnEnemy as a local variable twice. That's allowed (the second one hides the first where ever the second one is in scope) but that's not what you wanted.
You have correctly declared a local variable and captured it in showTitle. To set that very same variable later, use an assignment statement without prefixing it with local. You can assign it a function definition using the "anonymous" function syntax:
spawnEnemy = function()
...
end
Actually, in Lua, all functions are anonymous since they are just values. But, for debugging, it is helpful to have a name associated with a function. In stack traces, the name of the variable used to call the function is used, where possible.

Some insight on Object key accessing in lua

Im just alittle curious, as well as a bit confused. In my lua code im setting a new object like so from the start.
enemy = {};
enemy.__index = enemy;
function enemy.new(args)
Obj = {};
setmetatable(Obj,enemy);
Obj.name = "bullet";
Obj.x = args.x;
Obj.y = args.y;
Obj.spriteTexFile= "Invader.png";
Obj.sprite = display.newImage( Obj.spriteTexFile);
Obj.sprite:setReferencePoint ( display.TopLeftReferencePoint );
Obj.sprite.x = Obj.x;
Obj.sprite.y = Obj.y;
Obj.sprite.alpha = 0;
Obj.health = 100;
Obj.activeBul = false;
Obj.bullet = Bullet.new({x=Obj.sprite.x,y=Obj.sprite.y});
return Obj;
end
...
return enemy;
end
So when instantiating a new Enemy obj I call the new function above. NOW in the same file, a function in the Enemy Object I have the following function for example which allows me to acces the "self.bullet", a Bullet Object created when the Enemy is created. It also allows me to call the function trajectBullet in this Bullet instants.
function enemy:shoot()
local Bullet = require "Bullet";
local DEFAULTTIME = 5;--Movement time per space
self.bullet:trajectBullet({x=self.sprite.x,y=display.contentHeight, time =
DEFAULTTIME*display.contentHeight-self.sprite.y)});
end
My Question comes with a call like the following. If I try setting a property of a Bullet in this case, the owner property, i get a nil error and wont let me change it. If someone could help me understand alittle how accessing keys and properties really works that would help me out alot.
function enemy:setBulletOwner()
self.bullet.owner = self;
end
UPDATE:
bullet = {};
bullet.__index = bullet;
function bullet.new(arg)
local Obj = {};
setmetatable ( Obj, bullet );
Obj.sprite = display.newRect( 0, 0, 3, 7 );
Obj.sprite.x = arg.x;
Obj.sprite.y = arg.y;
Obj.sprite:setFillColor ( 255, 255, 255 );
Obj.sprite:setReferencePoint ( display.TopLeftReferencePoint );
Obj.owner = nil;
return Obj;
end
function bullet:trajectBullet(arg)
self.sprite.tween = transition.to(self.sprite,{ tansistion = easing.outExpo, y = arg.y, x=arg.x,time= arg.time,onComplete = function() bullet:cancelTween(self.sprite);
self.owner.sprite:dispatchEvent( {name = "canShootAgain"} ); end});
end
Keep in mind Obj.owner should be getting set from the function below.
function enemy:setBulletOwner()
print("BULLET MADE");
self.bullet.owner = self;
end
You should have your classes set up like this
Bullet
Bullet = {}
Bullet_mt = { __index = Bullet }
function Bullet:new(co_ordinates)
local obj = {x=co_ordinates[1],y=co_ordinates[2]}
obj.owner = "You" --etc...
return setmetatable(obj,Bullet_mt)
end
Enemy
Enemy = {slogan="Gettm!'"}
Enemy_mt = {__index = Enemy;}
function Enemy:new(args)
local obj = {}
--etc..
obj.bullet = Bullet:new({0,0})
return setmetatable(obj,Enemy_mt)
--alert return setmetatable(obj,getmetatable(self))
end
function Enemy:getBulletOwner()
return self.bullet.owner;
end
You shouldn't be requiring "Bullet" each time the enemy shoots in enemy:shoot. When you want to create a bullet for an enemy if you only want the enemy to have one bullet you should
create a new 'instance' of the bullet class and associate it with the key bullet like you've been doing obj.bullet= Bullet.new(...) but also introduce this functionality into a method of Enemy (so you can add a new bullet after the old one goes out of range etc...).
If a index doesn't exist within a table, it will go looking for the index in the table associated with __index in the metatable assigned to the table in question. As an example say a = Enemy:new(), and we wanted to find out the slogan of the enemy, via a.slogan we would look for the index slogan in a but not find it. So we would then go check what __index was associated with in the metatable of a, in this case Enemy. So we look for slogan in Enemy, it exists so we end up with `"Gettm!'".
Adding the following code beneath the class definitions
en = Enemy:new()
print(en:getBulletOwner())
print(en.slogan)
Produces
You
Gettm!'
Also be weary of the difference between a:b(arg1,arg2) and a.b(arg1,arg2). a:b(arg1,arg2) is essentially equivalent to a.b(a,arg1,arg2) where a is bound to self within the function. An example of this would be:
print(en.getBulletOwner())
produces
lua: l.lua:22: attempt to index local 'self' (a nil value)
while
print(en:getBulletOwner())
produces
You

Lua - Not displaying text in Corona SDK

In this app I'm creating with Corona SDK, when you win the text "You win" sould appear, but doesn't. I could post all the code, but I don't think the rest would be hepful, so here is only the essencial:
_H = display.contentHeight;
_W = display.contentWidth;
mRand = math.random;
o = 0;
time_remain = 20;
time_up = false;
total_orbs = 45;
total_secs = 20;
ready = false;
local backGround = display.newImage("media/bg.png");
backGround.xScale = 2;
backGround.yScale = 2;
loseMSG = display.newText("You Lose!", _W/2, _H/2, nil, 50)
loseMSG.isVisible = false
winMSG = display.newText("You Win!", _W/2, _H/2, nil, 50)
winMSG.isVisible = false
local countdowntxt = display.newText(time_remain, 0, 0, native.systemFont, 60);
countdowntxt.xScale = .5; countdowntxt.yScale = .5;
countdowntxt:setReferencePoint(display.BottomRightReferencePoint);
countdowntxt.x = _W-20; display.y = _H-20;
countdowntxt:setTextColor(0, 0, 0)
function winLose(condition)
if (condition == "Win") then
bgAlpha = display.newImage("media/bgAlpha.png");
bgAlpha.xScale = 2;
bgAlpha.yScale = 2;
winMSG.isVisible = true -- Here the win text should become visible, but doesn't
elseif (condition == "Fail") then
bgAlpha = display.newImage("media/bgAlpha.png");
bgAlpha.xScale = 2;
bgAlpha.yScale = 2;
loseMSG.isVisible = true
end
end
Any Ideas why?
You need to take a divide and conquer approach.
Does this work?
winMSG = display.newText("You Win!", _W/2, _H/2, nil, 50)
winMSG.isVisible = true <-- note this is set to true
It does?
Does winLose every get called? Put a print statement in it or a break point or whatever you use on your platform to debug.
It does?
What does the variable condition contain? Inspect it/print it out and verify that it is indeed "Win", same case, no spaces, etc. or you can put a print statement in the appropriate branch of that function to make sure it's being hit.
Is that OK?
Does it show up if you remove the bgAlpha code?
So on and so forth.
I don't know Corona, but Googling the docs for newText it's possible you have the parameters wrong (you're not passing a font).
I could post all the code
The less you post the better, because that means you've already gone through the steps shown above to try to isolate the problem. Nine times out of ten, doing that will reveal the problem all by itself.
Why have you given nil for font value?
Atleast pass the default system font
loseMSG = display.newText("You Lose!", _W/2, _H/2, native.systemFont, 50)
winMSG = display.newText("You Win!", _W/2, _H/2, native.systemFont, 50)

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