[MunkDev]

This is entirely implemented in Lua so you can just read the source code.

ObjectPoolMixin = {};
 
function ObjectPoolMixin:OnLoad(creationFunc, resetterFunc)
    self.creationFunc = creationFunc;
    self.resetterFunc = resetterFunc;
 
    self.activeObjects = {};
    self.inactiveObjects = {};
 
    self.numActiveObjects = 0;
end
 
function ObjectPoolMixin:Acquire()
    local numInactiveObjects = #self.inactiveObjects;
    if numInactiveObjects > 0 then
        local obj = self.inactiveObjects[numInactiveObjects];
        self.activeObjects[obj] = true;
        self.numActiveObjects = self.numActiveObjects + 1;
        self.inactiveObjects[numInactiveObjects] = nil;
        return obj, false;
    end
 
    local newObj = self.creationFunc(self);
    if self.resetterFunc then
        self.resetterFunc(self, newObj);
    end
    self.activeObjects[newObj] = true;
    self.numActiveObjects = self.numActiveObjects + 1;
    return newObj, true;
end
 
function ObjectPoolMixin:Release(obj)
    assert(self.activeObjects[obj]);
 
    self.inactiveObjects[#self.inactiveObjects + 1] = obj;
    self.activeObjects[obj] = nil;
    self.numActiveObjects = self.numActiveObjects - 1;
    if self.resetterFunc then
        self.resetterFunc(self, obj);
    end
end
 
function ObjectPoolMixin:ReleaseAll()
    for obj in pairs(self.activeObjects) do
        self:Release(obj);
    end
end
 
function ObjectPoolMixin:EnumerateActive()
    return pairs(self.activeObjects);
end
 
function ObjectPoolMixin:GetNextActive(current)
    return (next(self.activeObjects, current));
end
 
function ObjectPoolMixin:GetNumActive()
    return self.numActiveObjects;
end
 
function ObjectPoolMixin:EnumerateInactive()
    return ipairs(self.inactiveObjects);
end
 
function CreateObjectPool(creationFunc, resetterFunc)
    local objectPool = CreateFromMixins(ObjectPoolMixin);
    objectPool:OnLoad(creationFunc, resetterFunc);
    return objectPool;
end
 
FramePoolMixin = Mixin({}, ObjectPoolMixin);
 
local function FramePoolFactory(framePool)
    return CreateFrame(framePool.frameType, nil, framePool.parent, framePool.frameTemplate);
end
 
function FramePoolMixin:OnLoad(frameType, parent, frameTemplate, resetterFunc)
    ObjectPoolMixin.OnLoad(self, FramePoolFactory, resetterFunc);
    self.frameType = frameType;
    self.parent = parent;
    self.frameTemplate = frameTemplate;
end
 
function FramePool_Hide(framePool, frame)
    frame:Hide();
end
 
function FramePool_HideAndClearAnchors(framePool, frame)
    frame:Hide();
    frame:ClearAllPoints();
end
 
function CreateFramePool(frameType, parent, frameTemplate, resetterFunc)
    local framePool = CreateFromMixins(FramePoolMixin);
    framePool:OnLoad(frameType, parent, frameTemplate, resetterFunc or FramePool_HideAndClearAnchors);
    return framePool;
end