Concatenation problem

Getting Started Newbie Questions
#1

I have a table of units with their sprite information in it. I want to spawn the sprites, based on their id, but I get an error. I’ve tried looking on the Lua and Corona documentation, as well as in the forums and Stack Overflow, but I could not find a question related to this. 

The error I am getting is <name> expected near ‘…’:

characters. ..characters.units[k].id.. walking.sheet --Line with error

I don’t know how to fix the syntax. Thanks in advance!

#2

Again, the problem is you’re metaphorically trying to build a car engine before you’ve learnt to build an electrical circuit.

All I can tell you is you can’t have ‘characters.’ and then a space. The error is telling you it is expecting a ‘name’, or in other words a ‘child’ of characters, but it finds a space, and then the ‘…’, neither or which it wants.

#3

Thanks for this, Also, I do realize I have (a lot) more to learn, I just found out that the id I was trying to retrieve was nil.

#4

Oops, it was not nil, just had a typo.

#5

In the future if you do something like this and it doesn’t work:

characters. ..characters.units[k].id.. walking.sheet --Line with error

debug it on your own by verifying the parts:

-- Print the parts to make sure they are all valid print( "Parts", characters, k, walking ) -- Then start combining, one level at a time, till you find the problem print( "Combined", characters.units, walking.sheet ) print( "Combined", characters.units[k] ) print( "Combined", characters.units[k].id ) characters. ..characters.units[k].id.. walking.sheet --Line with error
#6

Of course, if you have SSK2, it provides table utilities to help with this.

print( k ) table.print\_r( characters ) table.dump( walking ) characters. ..characters.units[k].id.. walking.sheet --Line with error
#7

Finally, if this code is based on our other talk here: https://forums.coronalabs.com/topic/69092-how-can-i-require-this

Then the code I’m seeing makes no sense.  You can’t concatenate tables or display objects with …

walking.sheet is a sprite sheet instance.

#8

Oh. 

Also, this is my current code:

--characters.lua local m = {} m.units = { {img = "sprites/girl.png", timeBetweenAtk = 2350, name = "girl", cost = 75} } m.girl = {} m.girl.walking = {} local data = {width = 309, height = 494, numFrames = 10, sheetContentWidth = 1545, sheetContentHeight = 988} m.girl.walking.sheet = graphics.newImageSheet("sprites/walking-girl.png", data ) m.girl.walking.seq = {name = "walking", start = 1, count = 10, loopCount = 0, loopDirection = "forward"} m.girl.primaryAtk = {} local data = {width = 385, height = 477, numFrames = 10, sheetContentWidth = 1925, sheetContentHeight = 954} m.girl.primaryAtk.sheet = graphics.newImageSheet("sprites/melee-girl.png", data) m.girl.primaryAtk.seq = {name = "melee", start = 1, count = 10, loopCount = 0, loopDirection = "forward"} m.girl.idle = {} local data = {width = 271, height = 473, numFrames = 10, sheetContentWidth = 813, sheetContentHeight = 1892} m.girl.idle.sheet = graphics.newImageSheet("sprites/idle-girl.png", data) m.girl.idle.seq = {name = "idle", start = 1, count = 10, loopCount = 0, loopDirection = "forward"} return m 

--main.lua for k = 1, #imgSet do local identifier = characters.units[k].name local function spawnCharacter(event) if event.phase == "began" then if moneyCount \< characters.units[k].cost then print("insufficient funds") else moneyCount = moneyCount - characters.units[k].cost moneyText.text = moneyCount .. " / " .. moneyWallet local unit = display.newSprite(characters.identifier.walking.sheet, characters.identifier.walking.seq) end end return true end imgSet[k]:addEventListener("touch", spawnCharacter) end

I was just trying to find a good way to spawn an individual unit if there are 10 to choose from.

#9

I have tried concatenating the string into the image file, but I can’t use the data, because I can’t concatenate.

for i = 1, #m.units do identifier = m.units[i].name end function m.spawnUnit(identifier) local unit = ???? end

If this was for only two characters it would be easy, but I want this to work for dozens if not hundreds of characters.

#10

I have one thing to say (based on all your posts)… walk before you run!

Start simple and when you completely understand then add more functionality bit by bit.

#11

You are right, I think I have put too much on top of the building, instead of focusing on the base. 

#12

Would you just happen to know where I can find the info for a way to do this?

#13

“concatenation” is probably not the word.  seems the real topic s/b this access method:

characters[identifier].walking.sheet

instead of existing:

characters.identifier.walking.sheet
#14

I did not think of that! That could actually work. I’m just having trouble adjusting my code.

#15

Finally got it!

--characters.lua m.units = { {img = "sprites/girl.png", timeBetweenAtk = 2350, name = "girl", cost = 75, respawnTime = 3750, state = active} } m.girl = {} m.girl.walking = {} local data = {width = 309, height = 494, numFrames = 10, sheetContentWidth = 1545, sheetContentHeight = 988} m.girl.walking.sheet = graphics.newImageSheet("sprites/walking-girl.png", data ) m.girl.walking.seq = {name = "walking", start = 1, count = 10, loopCount = 0, loopDirection = "forward"} --main.lua local charToSpawn = characters.units[k] local identifier = charToSpawn.name if event.phase == "began" then if moneyCount \< charToSpawn.cost then print("insufficient funds") else moneyCount = moneyCount - charToSpawn.cost moneyText.text = moneyCount .. " / " .. moneyWallet local charWalkingData = characters[identifier].walking local unit = display.newSprite(charWalkingData.sheet, charWalkingData.seq) end end
#16

Again, the problem is you’re metaphorically trying to build a car engine before you’ve learnt to build an electrical circuit.

All I can tell you is you can’t have ‘characters.’ and then a space. The error is telling you it is expecting a ‘name’, or in other words a ‘child’ of characters, but it finds a space, and then the ‘…’, neither or which it wants.

#17

Thanks for this, Also, I do realize I have (a lot) more to learn, I just found out that the id I was trying to retrieve was nil.

#18

Oops, it was not nil, just had a typo.

#19

In the future if you do something like this and it doesn’t work:

characters. ..characters.units[k].id.. walking.sheet --Line with error

debug it on your own by verifying the parts:

-- Print the parts to make sure they are all valid print( "Parts", characters, k, walking ) -- Then start combining, one level at a time, till you find the problem print( "Combined", characters.units, walking.sheet ) print( "Combined", characters.units[k] ) print( "Combined", characters.units[k].id ) characters. ..characters.units[k].id.. walking.sheet --Line with error
#20

Of course, if you have SSK2, it provides table utilities to help with this.

print( k ) table.print\_r( characters ) table.dump( walking ) characters. ..characters.units[k].id.. walking.sheet --Line with error