WoWInterface - How to properly use CreateFramePool() ?

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How to properly use CreateFramePool() ?

I've been seeing a lot of Blizzard code using CreateFramePool() and I'm wondering if it's worth using this myself as opposed to creating my own stack-like data structure. However, maybe it does something more than this but I can't find any documentation on it.

This is the content found inside a returned frame pool object:

ReleaseAll
achieveObjects
numActiveObjects
inactiveObjects
GetNumActive
resettingFunc
OnLoad
creationFunc
EnumerateActive
Release
Acquire
GetNextActive
EnumerateIntactive

My question is this: Is there any documentation on how to use this?

I'm assuming that you can disable/enable frames from the pool using:

Lua Code:

local pool = CreateFramePool()
local frame = pool:Acquire() -- uses an inactive frame or creates one with "creationFunc" function
pool:Release(frame) -- not really sure if this is the correct way to disable the frame
 
-- something is always true. Maybe it represents if the frame is active, but since I am iterating over only active frames this seems pointless
for frame, something in pool:EnumerateActive() do
    -- run code to update your frame (could be a buff icon for example)
end

Not sure what OnLoad does. Does it run when a frame becomes active?

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

Lua 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

This is perfect. I wasn't sure what the main object was called. Thank you!
I'll start running some tests and figure out how it all fits together :)

Once I understood what this frame pool did, I created a very simple version I use in Decliner for generating OnUpdate responses to some filters. This way, I don't need several dedicated OnUpdate frames, just a dynamic pool that uses the first unused frame or creates a new one that adds to the pool when finished. Blizzard's way is definitely more sophisticated and made for different scenarios, but if you just need a disposable OnUpdate frame with one piece of data included in the frame, you could try what I did.

Lua Code:

local pool={}
function f.pool(t,i)
    if i then
        pool[i]:SetScript('OnUpdate',nil)
        pool[i].t=nil
        return
    end -- function was called with an index, terminate frame at that index
    for i=1,#pool do
        if pool[i] and not pool[i].t then
            pool[i].t={i=i,t=t}
            return i
        end -- loop through frames to find an unused one and return the index, putting "t" into the frame
    end
    insert(pool,CreateFrame('frame'))
    i=#pool
    pool[i].t={i=i,t=t}
    return i -- no unused frames found, generate a new one and return its index, also putting "t" into the frame
end

An example of usage is the following response to blocked guild invites:

Lua Code:

pool[f.pool((GetCVar('Sound_EnableSFX')))]:SetScript('OnUpdate',function(self)
    SetCVar('Sound_EnableSFX',self.t.t)
    f.pool('',self.t.i)
end)
SetCVar('Sound_EnableSFX','0')

This calls a frame directly from the pool table, while getting the index from f.pool's return and putting the current SFX setting into the "t" key of the frame. Then I turn off SFX. Once the OnUpdate fires a frame later, reset SFX and release the frame using its index stored in the "i" key.

This completely blocks the "level up" sound when someone invites you to a guild.

I'm sure there's a cleaner way to do what I did, but it works for me.

@Kanegasi I've made a few things like this myself for a timer bars tracking addon except it executes the update function for each frame in the pool iteratively and probably not as intricate as your interesting design. Thanks for the example, I like it. Gives me a new approach to consider.

It's mostly good for when you want to fill a list of objects, was messing around with this one and texturepools.