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32 lines of goodness
| This library has problems when a two classes inherit from the same base class. Check the thread for more details. |
The Libary
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})
if newvalue.__init then
newvalue:__init(...)
end
return newvalue
end
end
function class(name)
local newclass = {}
_G[name] = newclass
return setmetatable(newclass, {__index = mt_class, __call = define})
end
That's all there is to it! Just 32 lines!
Usage
Slap the above library in a file of your choose (maybe "32log.lua") and include it in your code using the require function.
The basic syntax is as follows:
memberName = nonNilValue;
}
Once a class has been created you can create new instances of the class as follows:
If you create a method named __init it can be used to as a constructor with new.
x = 0;
y = 0;
z = 0;
}
function Vector:__init(x, y, z)
self.x = x
self.y = y
self.z = z
end
function Vector:print()
print(self.x, self.y, self.z)
end
local vec = Vector:new(1, 0.5, 0.25)
vec:print()
Whatever value you set a member to in the definition, it will act as a default value for the member. This works well with values like numbers and strings where they are always copied by value but tables can get a little tricky:
bar = {};
}
local foo = Foo:new()
foo.bar["foobar"] = 10;
local foo2 = Foo:new()
print(foo2.bar["foobar"])
Classes inherit their parent's default member values and meta-methods. You can also call a parent's method that was overloaded in the derived class using the super member:
function Base:foobar()
print("foo")
end
class "Derived" : extends(Base) {}
function Derived:foobar()
self.super.foobar(self)
print("bar")
end
See Also
Post any questions you might have in the original post.
