Getting table of all objects of class (OOP)

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#1

Lets say we have this:

local obj = {}
obj.__index = obj

function obj.new(someProperty)
    local newObj = {}
    setmetatable(newObj,obj)

    newObj.someIndex = someProperty
    return newObj
end

for i = 1, 10 do
   obj.new("some value")
end

How would I receive every single object of the obj class? Pardon any errors with the code, I threw this together just right now

1 Like
#2

I would simply make a table of all objects that are instantiated;
like this:

local obj = {}
obj.__index = obj

local objects={}

function obj.new(someProperty)
    local newObj = {}
    setmetatable(newObj,obj)

    newObj.someIndex = someProperty
    table.insert(objects, newObj);
    return newObj
end

for i = 1, 10 do
   obj.new("some value")
end
2 Likes
#4

@blokav, @Fionist12, I considered both of these approaches before posting but I also require a way to remove it from the “objects” folder, which I can’t find a way to accomplish.

function obj:Destroy()
    setmetatable(self,nil)
    -- code to remove obj from table
end

Using this doesn’t seem to cut it:

function obj:Destroy()
    setmetatable(self,nil)
    objects[table.find(objects,self)] = nil
end
#5

you could add a destructor to each object. A destructor is basically a method that you call to to destroy an object. This is the approach that languages like C++, and Java take, and I believe is what happens when you do Instance:Destroy()

so something like: obj:Destruct(), and all that it would do is remove the object from the table

#6

Doing that will make the object an empty table and keep it in the “objects” table which is not what I am looking for.

#7

oh wait, i’m sorry, I didn’t read the proceeding post correctly;
u could add another function to the class - not the objects - that takes an object and removes it from the table.

like maybe: obj:Remove(object);

#8

That’s precisely what I’m having trouble with. When using table.insert, it doesn’t give me the key that the value was assigned with, leaving me with no way to locate the object in the table and call Destroy on it.

#9

you can use table.remove(objects, table.find(objects, object))

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#10

You can always use the object itself as the key.

function obj.new()
	local newObj = blah blah blah...
	objects[newObj] = true
end

function obj:Destroy()
	objects[self] = nil
end

for object, _ in pairs(objects) do
	print(object.someProperty)
end
#13

if you can do: table.insert(objects, obj) then it means you already have access to the objects; so from that you can then simply do obj:Destroy() or classname:Remove(obj)

#14

You can use almost any data type as a dictionary key in lua.

#16

i mean you shouldn’t have to. Since the objects will be added to the table when they are constructed.

#17

just an idea but you can index each object when they are constructed so each one is unique

2 Likes
#18

Tables aren’t like other data types in that they are unique to themselves, regardless of what they contain. This is why you have to deep copy tables and more. If you index by the object itself, it wouldn’t get confused with identical objects.

Edit: You should try to learn more about lua on your own before incorrectly discrediting other users’ suggestions. Indexes can be data types other than numbers and strings. Indexing the object itself should have no problem with “identical objects”.

4 Likes
#20

did ur issue resolved? send me a message if not

1 Like
#21

Issue resolved. Thanks to everyone replied, including you.

1 Like