尝试调用方法“ removeSelf”（nil值）

Question

For some reason I can't remove a group object, even though I check if it's nil or not

First thing I tried:

if playGroup~=nil then 
   playGroup:removeSelf() 
end

ERROR: Attempt to remove an object that's already been removed from the stage or whose parent/ancestor group has already been removed.

I also tried this:

for k,v in pairs(playGroup) do
    if k ~= nil then
        k:removeSelf()
    end
end

ERROR: attempt to call method 'removeSelf' (a nil value)

Answer 1

You should destroy v and not k:

for k,v in pairs(playGroup) do
  if v ~= nil then
     v:removeSelf()
  end
end

Answer 2

You do not need to remove objects from a group, Corona does it for you when you remove the group. So the loop (even after the fix proposed by hades2510), is not required.

The error you get, "Attempt to remove an object that's already been removed..." suggests that playGroup is a regular table rather than a display object. Calling removeSelf on a display object removes Corona-related entries, leaving the object as a regular table. So there are at least these possibilities:

• it could be that your code has already removed playGroup as part of another event handler, or
• the handler was called a second time, or
• playGroup was created as a regular table rather than a display object.

One thing you could do is set playGroup = nil after removeSelf so that if Corona comes across that if block again, it will not attempt to remove it again:

if playGroup ~= nil then 
    playGroup:removeSelf() 
    -- now playGroup is plain table
    -- dont' want to run this block of code again: 
    playGroup = nil
end

If this does fix the problem, it is probably still worth determining why the if block gets called after playGroup has been removed from display. A print statement, without setting playGroup to nil, will do the trick:

if playGroup ~= nil then 
    print('WARNING: Going to remove play group from display')
    playGroup:removeSelf() 
    print('WARNING: Play group removed from display')
end

Once you know the reason, you can add back the playGroup = nil .

Answer 3

Make sure you have inserted the object in your table or group. If you don't insert the object in table or group and try to remove it, then this error will produce.