32LogEx

[Centauri Soldier]

I decided to modify the wondeful 32 Lines of Goodness to suit my own project and it turned out to be pretty useful for more than that one project. So, I thought I'd share it here for anyone else who might need such functionality. I know, it's not 32 lines anymore. I left that in the name to honor the original author.

32LoGEx now allows for all metamethods for your custom class.
32LoGEx now creates a pseudo-type for your custom class which can be returned by the lua type() function.

For those of you who've never used 32log, it's a system designed for creating classes with much OOP behaviour.

Example:

class "MyClass" {};
local obj = MyClass:new();
Dialog.Message("Type", type(obj));

--[[
This is a modification of the '32 Lines of Goodness' found at https://love2d.org/wiki/32_lines_of_goodness.

Added Features:
    Allows the creation of all known metamethods for each class.
        E.g.,
        class "MyClass" {};
        function MyClass:__tostring() return "This is what I want to return." end
        local obj = MyClass:new();        
        print(tostring(obj));
        -> Output would be "This is what I want to return."
    Creates pseudo-types of each class created by overriding the lua type() function.
        E.g.:
        class "CoolClass" {};
        local obj = CoolClass:new();
        print(type(obj));        
        -> output would be "CoolClass"
        

Copyright © 2019 AMSPublic.org

This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

    1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
    2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
    3. This notice may not be removed or altered from any source distribution.
]]

local mt_class = {}
 
function mt_class:extends(parent)
    self.super = parent
    setmetatable(mt_class, {__index = parent})
    parent.__members__ = parent.__members__ or {}
  
    return self
end
 
local function define(class, members)
    class.__members__ = class.__members__ or {}
  
    for k, v in pairs(members) do
        class.__members__[k] = v
    end
  
    function class:new(...)
        local newvalue = {}
        
        for k, v in pairs(class.__members__) do
            newvalue[k] = v
        end
              
        setmetatable(newvalue,
                        {
                            __index =         class,
                            __add =         class.__add,
                            __concat =        class.__concat,
                            __div =            class.__div,
                            __eq =            class.__eq,
                            __le =            class.__le,
                            __len =            class.__len,
                            __lt =            class.__lt,
                            __mod =            class.__mod,
                            __mul =            class.__mul,
                            __newindex =     class.__newindex,
                            __pow =            class.__pow,
                            __sub =            class.__sub,
                            __tostring =     class.__tostring,
                            __type =        class.__type,
                            __unm =            class.__unm,
                            
                        }
                    );
      
        if newvalue.__init then
            newvalue:__init(...);
        end
      
        return newvalue;
    end
    
end

function class(name)
    local newclass = {
        __add =         function() end,
        __concat =         function() end,
        __div =         function() end,
        __eq =             function() end,
        __le =             function() end,
        __len =         function() end,        
        __lt =             function() end,
        __mod =         function() end,
        __mul =         function() end,
        __newindex =     function() end,
        __pow =         function() end,
        __sub =         function() end,
        __tostring =     function() end,
        __type =        name,
        __unm =         function() end,        
    };
    
    _G[name] = newclass;
  
    return setmetatable(newclass, {__index = mt_class, __call = define});
end

local _type = type;
function type(vObj)
    local sType = _type(vObj);
    
    if (sType == "table") then
    
        local tMeta = getmetatable(vObj);
        
        if (tMeta) then
        
            if (tMeta["__type"]) then
                sType = tMeta["__type"];
            end
            
        end
        
    end

    return sType;
end

[Centauri Soldier]

Well poo. After about 2 hours of debuggin my code, I discovered that there's nothing wrong with my code. It works fine with modern lua, it just doesn't work with AMS. The lua shipped with AMS is several years out of date :(.

[Imagine Programming]

Well poo. After about 2 hours of debuggin my code, I discovered that there's nothing wrong with my code. It works fine with modern lua, it just doesn't work with AMS. The lua shipped with AMS is several years out of date :(.

AMS ships with Lua 5.1, which is extremely out of date. It's still the most used Lua version I believe, mainly because LuaJIT is so popular (which implements the 5.1 syntax)

What didn't work in the AMS version?

[Centauri Soldier]

It throws an error about a loop in gettable here...

if newvalue.__init then
    newvalue:__init(...);
end

But when I test it with lua 5.4 it works fine.

EDIT: just to be clear, the error happens when using the :extends() function. But this error does not occur when using newer versions of lua.

[Imagine Programming]

It throws an error about a loop in gettable here...

if newvalue.__init then
newvalue:__init(...);
end

But when I test it with lua 5.4 it works fine.

EDIT: just to be clear, the error happens when using the :extends() function. But this error does not occur when using newer versions of lua.

        if rawget(newvalue, "__init") then
            rawget(newvalue, "__init")(newvalue, ...);
        end

Try that. newvalue.__init causes newvalue_metatable.__index to be indexed for the key "__init", so it might loop indefinitely trying to get a value that does not exist. When you use rawget, you bypass the metatable and get the "__init" key directly from the table. I've noticed that it happens more though, not just at that point. This code, was it written for Lua 5.1?

[Imagine Programming]

Try this, I made one based on something quite big I'm working on (unrelated to AMS). This one basically does what you want.
Mind you though, I think you were using the other version wrong initially, it requires you to define the members in the `{}` block.

Anyhow, let me know what you think. See globals and on show

[Centauri Soldier]

I'm looking at your example now, it's quite extensive, I'll be a little while figuring it out. Thanks for taking the time to make this!
Also, I think you might be right about the original script. After looking over some other code I'm working on, I've noticed a few things that may have been causing problems in this code.

EDIT: I was in Globals when I posted initially, then just noticed your code in the OnShow event with the debug opening. So epic, thanks again, Bas.

[Centauri Soldier]

Well, that code is pretty **** amazing. I'm getting it work with my old classes but I have one confusing item I can't seem to sort out. I've noticed that I can declare method elements by fiat within a member method but I can't seem to figure out how to delcare elements outside a member method within a class table. When I do, I get an error saying that settings those values will overwrite a method (even though the values are numbers). If I declare them within a table it works but, for some reason, an error is thrown whenever I try to declare something like Var = 12;

class "Iota" {
    
    Years = 0;
    Days = 0;
    Hours = 0;
    Minutes = 0;
    Seconds = 0;
    
    __construct = function(...)
        --AAA.CheckCount("Iota", "__construct", arg, 5);
        --AAA.CheckTypes("Iota", "__construct", {self}, 1, {"Iota"});
        local this = arg[1];
        local nYears = AAA.CheckTypes("Iota", "__construct", arg, 2, {"number"});
        local nDays = AAA.CheckTypes("Iota", "__construct", arg, 3, {"number"});
        local nHours = AAA.CheckTypes("Iota", "__construct", arg, 4, {"number"});
        local nMinutes = AAA.CheckTypes("Iota", "__construct", arg, 5, {"number"});
        local nSeconds = AAA.CheckTypes("Iota", "__construct", arg, 6, {"number"});
        
        this.Years = nYears;
        this.Days = nDays;
        this.Hours = nHours;
        this.Minutes = nMinutes;
        this.Seconds = nSeconds;
        this:LevelValues();
    end;
    
    
    __tostring = function(...)
    local this = arg[1];
    
    return this.Years..':'..
           string.format("%03d:%02d:%02d:%02d",
           this.Days, this.Hours,
           this.Minutes, this.Seconds);
    end
    
    --[[Years = 0,
    Days = 0,
    Hours = 0,
    Minutes = 0,
    Seconds = 0,    ]]
}

EDIT: After a few hours of working with this code in my project I think I'm starting to understand it a bit more. It's very powerful!
Do you think there'd be anyway to implement this.SOMEVAR as a local? Currently all variables set in the contructor are global. I'm not seeing a way to make them local but maybe you can see something I don't. I know I could do it with methods and variables declared outside of the class declaration, I was just wondering if it were possible with 'this' (the class passed).

EDIT 2: I found a pretty good way to do it. I create a local table in the parent class and every class constructor has this inside.
For my Card class...

tCard[this] = {};

My solution to my problem of encapsulation is not a perfect one but it works rather well. I can access the data from inside the classes but not from outside.

[Imagine Programming]

I'm not quite sure what you mean by setting it as local vs global;

Any property specified in any member (constructor or method) using `this.name = value` is a property of the current object, so neither local or global.

Regarding the error you see about overwriting an existing member, I didn't implement declaration of properties (your Years, Days, ... properties). Those are
considered members and members shouldn't be overwritten in this implementation. I followed the Python/Javascript/PHP approach; you can declare all your
members in any method at any point.

__construct = function(...)
    --AAA.CheckCount("Iota", "__construct", arg, 5);
    --AAA.CheckTypes("Iota", "__construct", {self}, 1, {"Iota"});
    local this = arg[1];
    local nYears = AAA.CheckTypes("Iota", "__construct", arg, 2, {"number"});
    local nDays = AAA.CheckTypes("Iota", "__construct", arg, 3, {"number"});
    local nHours = AAA.CheckTypes("Iota", "__construct", arg, 4, {"number"});
    local nMinutes = AAA.CheckTypes("Iota", "__construct", arg, 5, {"number"});
    local nSeconds = AAA.CheckTypes("Iota", "__construct", arg, 6, {"number"});
    
    this.Years = nYears;
    this.Days = nDays;
    this.Hours = nHours;
    this.Minutes = nMinutes;
    this.Seconds = nSeconds;
    this:LevelValues();
end;

That alone should be enough

[Centauri Soldier]

Thanks for clarifying that for me. I see what you're going for now.

In answer to your question, I was referring to something like Ammo.Amount being accessible globally. But I figured out to provide encapsulation when needed using 'this' in local tables.

This really helped me a lot, thanks again, Bas, you're a life saver .

[Imagine Programming]

Thanks for clarifying that for me. I see what you're going for now.

In answer to your question, I was referring to something like Ammo.Amount being accessible globally. But I figured out to provide encapsulation when needed using 'this' in local tables.

This really helped me a lot, thanks again, Bas, you're a life saver .

Glad I could help!

Edit - Some low-level optimization tips; https://luac.nl/s/161a434799211397f9b878ab1

[Centauri Soldier]

Wow, that's neat! I didn't even know there a tool like that out there. Good to know, thanks.

Oh, I noticed a strange bug the class code. When you try to extend a class more than once (such as Creature -> Human -> Soldier) it creates an infinite callback loop when calling this:super() in the __constructor metamethod of each class. It's because the "this" that comes through is the sub-class and so it just keeps calling itself over and over until it hits a stack overflow. I have found a partial solution by calling the parent-to-be's class directly (instead of using super()) in the child constructor but I wonder if it's possible to make it work natively in the class code. What do you think?

EDIT: I found an even better way to do it as-is.

Since calling this:super() creates an infinite loop and calling MyClass() in the constructor does not associate it
with the subclass, niether option is a viable, working solution; however, by calling MyParentClass:super() explicitly in each constructor (as opposed to this:super()), the infinite loop is avoided and the classes are correctly associated.

[Imagine Programming]

Wow, that's neat! I didn't even know there a tool like that out there. Good to know, thanks.

Oh, I noticed a strange bug the class code. When you try to extend a class more than once (such as Creature -> Human -> Soldier) it creates an infinite callback loop when calling this:super() in the __constructor metamethod of each class. It's because the "this" that comes through is the sub-class and so it just keeps calling itself over and over until it hits a stack overflow. I have found a partial solution by calling the parent-to-be's class directly (instead of using super()) in the child constructor but I wonder if it's possible to make it work natively in the class code. What do you think?

EDIT: I found an even better way to do it as-is.

Since calling this:super() creates an infinite loop and calling MyClass() in the constructor does not associate it
with the subclass, niether option is a viable, working solution; however, by calling MyParentClass:super() explicitly in each constructor (as opposed to this:super()), the infinite loop is avoided and the classes are correctly associated.

Nice find, yes in my original implementation each object has a reference to its concrete class implementation; that way I always have the valid super class available. I missed that in this implementation.

The luac.nl tool is reasonably new, by the way. It's something I released a little while ago.

[Centauri Soldier]

Lol, I just noticed I have about 3 million grammar and spelling errors in my last post :P. I'll just pretend I didn't see those.

So, the solution I thought I found doesn't actually work because 'this' in any constructor past the first parent is considered a type() "class". I did really find a solution this time, albeit not a very elegant or robust one.

           class_object.super2nd = function(instance, ...)
                local parent = getmetatable(class_object).__parent;
                if (parent) then
                    local grandParent = getmetatable(parent).__parent;                
                    if (grandParent and type(grandParent.__construct) == "function") then
                        grandParent.__construct(instance, ...);                    
                        return;
                    end
                end
            end
            
            class_object.super3rd = function(instance, ...)
                local parent = getmetatable(class_object).__parent;
                if (parent) then
                    local grandParent = getmetatable(parent).__parent;
                    if (grandParent) then
                        local greatGrandParent = getmetatable(grandParent).__parent;
                        if (greatGrandParent and type(greatGrandParent.__construct) == "function") then
                            greatGrandParent.__construct(instance, ...);                    
                            return;
                        end
                    end
                end
            end

[Imagine Programming]

Can you share code that reproduces the issue you were initially talking about?