Gideros class

zoolax · January 2013

I know in lua you can fake OOP by doing

--regular way
--This is what I am used too.
local player ={}
--Do your methods here
return Player

--Gideros:
Player = Core.class(Sprite)
function Player:init()
--Some vars
end
--Create some methods

Is making the class in Gideros way will make the app more optimized?
Thanks again in advance

john26 · January 2013

Here's my understanding of what you call the regular way

function newdog(c)
  local dog={colour=c, speak=function(self) print ("woof! My colour is:",self.colour) end}
  return dog
end
 
fido=newdog("blue")
fido:speak() -- output: woof! My colour is blue

So newdog is a factory function that returns dogs. You can also pass initialisation info through. In this case the dog's colour.

However, with this inheritance is not so easy. You could do

function newAlsatian(b,c)
  local alsatian=newdog(c)
  alsatian.breed=b
  alsatian.speak=function(self) print("How do you do? My breed is",self.breed) end
  return alsatian
end

which is maybe not so elegant but it does give you very explicit control over initialisation. In another thread people are confused about the automatic initialisation in Gideros so maybe this way is better, more verbose but less confusing..?

But in the Lua manual chapter on OO, it recommends a different way using metatables and I think that's what Gideros is using. I've never really understood what metatables do and not sure why this is better than the way just described...?

zoolax · January 2013

@john,
Thanks john:)

BJG · January 2013

I wish I understood this stuff more clearly. I'll have to stare at that example for a while.

Platypus · April 2013

Using two full stops instead of commas seems to make the spacing nice.

function newdog(c)
  local dog={colour=c, speak=function(self) print ("(Woof!) I am a "..self.colour.." dog.") end}
  return dog
end
 
fido=newdog("blue")
fido:speak() -- output: (Woof!) I am a blue dog.

function newdog(c)
  local dog={colour=c, speak=function(self) print ("(Woof!) I am a",self.colour,"dog.") end}
  return dog
end
 
fido=newdog("blue")
fido:speak() -- output: (Woof!) I am a	blue	dog.

Edit:
Caution, beginners (like me)! - Please read OZApps' comment below.

OZApps · April 2013

@Platypus, the only issue with the '..' which is the concatenation operator in Lua is that if one of the value is 'nil' then it will throw an error, however with a coma ',' it will print is irrespectively.

Platypus · April 2013

Oh! I see.

Thanks, @OZApps.

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