Lua Classes

[adriweb]

Here's the source code of the class() function, that TI uses :


(not tested)

Code: Select All | Copy To Clipboard

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-- Class definition system class = function(prototype)     local derived = {}     local derivedMT = {         __index = prototype,         __call  = function(proto, ...)             local instance = {}             local instanceMT = {                 __index = derived,                 __call = function()                     return nil, "attempt to invoke an instance of a class"                 end,             }             setmetatable(instance, instanceMT)             if instance.init then                 instance:init(...)             end             return instance         end,     }     setmetatable(derived, derivedMT)     return derived end

Paste that and use  blablabla=class()  now

[Jim Bauwens]

You can, but it works in a different way then the calculator way.
1. Its not event based (but you can make it like that)
2. It has no gc like we now on the calculator
3. Standard is only console, but you can add gui support by installing modules (or rocks).

Edit, thanks Adriweb

[Nick]

well yeah, i found this one: http://www.tecgraf.puc-rio.br/iup/
i'll study it..

and how can you make it event-based?

i know some visual basic, will that help?

[Jim Bauwens]

You just make a loop were you call certain functions when certain stuff are true
Visual basic has nothing to do with Lua

[flyingfisch]

Here's the source code of the class() function, that TI uses :


(not tested)

Code: Select All | Copy To Clipboard

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

-- Class definition system class = function(prototype)     local derived = {}     local derivedMT = {         __index = prototype,         __call  = function(proto, ...)             local instance = {}             local instanceMT = {                 __index = derived,                 __call = function()                     return nil, "attempt to invoke an instance of a class"                 end,             }             setmetatable(instance, instanceMT)             if instance.init then                 instance:init(...)             end             return instance         end,     }     setmetatable(derived, derivedMT)     return derived end

Paste that and use  blablabla=class()  now

So this should work in luaFX also?

[Jim Bauwens]

Yes, it will

[flyingfisch]

OK, so now my question is, what is so special about classes and how can I take advantage of them?

And thanks for answering all my stupid questions jimbauwens

[adriweb]

https://github.com/adriweb/Nspire-BreakOut/blob/master/BreakOut.lua

take a look at this code (I made it so it can be helpful for beginners and people who want to learn class-oriented lua programming on the Nspire) and try to understand a way I could have had as many balls, blocks etc. as I wished without using classses and without having to write everything for each object.

Have fun

(btw,  it's almost impossible)

That's what classes are for : creating once and for all, a "definition" of objects, and creating as many objects as you want of that class, so they will inherit the class properties.

Google "object oriented programming" and you'll see in detail what I mean.

[Levak]

The principle of classes / objects is simple : you can make copies of it, you can duplicate much much time and reach a certain amount of variables that you can't manage without (or with arrays but ... well you get it).
An object represents a bunch of preperties and a bunch of methods ALL related to this "kind" of object.
That way you won't have troubles to find other function names for this, this or that. Here is an example : "vector1_toString", "vector2_toString" etc... this is bad and painful, just define it once and call the object "vector" and the method name "toString", then, make bunch of that object.

This is a general approach. Now, I'm giving you a _real_ example : Imagine a bunch of aliens sprites and a spaceship (space invaders thus). How are you going to store each aliens positions ?
You can make two arrays, one for x, one for y. Ok. But then you have to manage somthing else : the spaceship position. Another varname x and another y. You reached 2 arrays and 2 vars.
Now let's see with classes : An array of "SpaceShipSprite" objects (aliens), and another "SpaceShipSprite" object for the space ship.
Each position is object.x and object.y (for example) and you only have to manage 1 array and 1 object.

You see now ?

Secondly, classes makes your code looking clever, sperated in multiple files, each file is related for one object and co..

[flyingfisch]

The principle of classes / objects is simple : you can make copies of it, you can duplicate much much time and reach a certain amount of variables that you can't manage without (or with arrays but ... well you get it).
An object represents a bunch of preperties and a bunch of methods ALL related to this "kind" of object.
That way you won't have troubles to find other function names for this, this or that. Here is an example : "vector1_toString", "vector2_toString" etc... this is bad and painful, just define it once and call the object "vector" and the method name "toString", then, make bunch of that object.

This is a general approach. Now, I'm giving you a _real_ example : Imagine a bunch of aliens sprites and a spaceship (space invaders thus). How are you going to store each aliens positions ?
You can make two arrays, one for x, one for y. Ok. But then you have to manage somthing else : the spaceship position. Another varname x and another y. You reached 2 arrays and 2 vars.
Now let's see with classes : An array of "SpaceShipSprite" objects (aliens), and another "SpaceShipSprite" object for the space ship.
Each position is object.x and object.y (for example) and you only have to manage 1 array and 1 object.

You see now ?

Secondly, classes makes your code looking clever, sperated in multiple files, each file is related for one object and co..

Oh, wow, I've been wondering how to do this for a while! Now I understand what classes are for! THX!!!!

[Nick]

Secondly, classes makes your code looking clever, sperated in multiple files, each file is related for one object and co..

how can you do this? i mean, writing every method/class in a seperate file would be sooo useful Ö

[Levak]

Secondly, classes makes your code looking clever, sperated in multiple files, each file is related for one object and co..

how can you do this? i mean, writing every method/class in a seperate file would be sooo useful Ö

For a while here (like 6 months now ) :
http://levak.free.fr/ftp/nspire/Make3D/

[Jim Bauwens]

Or check EEPro.

Also Levak, I was before you.

* jimbauwens runs

[Levak]

Or check EEPro.

Also Levak, I was before you.

* jimbauwens runs

Never said I was first Ö
Basicly, it's Makefile based (or bash like me), you have to concatenate each files in a single Lua file (or xml for the Library version of Make3D)

[adriweb]

Secondly, classes makes your code looking clever, sperated in multiple files, each file is related for one object and co..

how can you do this? i mean, writing every method/class in a seperate file would be sooo useful Ö

Example for EEPro, indeed :