display.remove equivalents

Solar2D General Questions/Discussion
#1

Hi guys,

Is

display.remove (myGroup)
myGroup = nil

same as:

for i = 1, myGroup.numChildren do
display.remove (myGroup[i])
myGroup[i] = nil
end

Or I will have memory leak if I do not tie each child to nil (in first case)?

Many thanks!
Ivan

#2

Answer - As long as there are no external references to the objects, simply removing the group and nill-ing any references to the group will be leak-less:

local myGroup = display.newGroup() ... then later display.remove (myGroup) myGroup = nil

Quick FYI, you don’t need to assign nil in the second snippet:

for i = 1, myGroup.numChildren do display.remove (myGroup[i]) end

Please remember to format all code posts.
formatyourcode.jpg

#3

Sorry for not formatting it (it is not easily done while on mobile version).

Can you name one/two examples for  external references to the objects ?

Thanks!

#4

I mean if you have other variables referencing the objects you’re deleting then the objects won’t be garbage collected till those variables are cleared or fall out of scope.

I simply could not assume (in my answer) that you only put the objects in a display group.  I didn’t know if you’d also used variables somewhere to refer to specific objects in that group.

#5

Can you give one simple example?

Word variable is not so clear… 

#6 
local group = display.newGroup() display.newCircle( group, 10, 10, 10 ) -- 1 local tmp = display.newCircle( group, 10, 10, 10 ) -- 2 display.newCircle( group, 10, 10, 10 ) -- 3 display.remove( group ) group = nil -- Circle 1 and 3 are removed and will be garbage collected. -- Circle 2 (referenced by variable 'tmp') is removed, but will not be -- garbage collected till 'tmp' is nilled or falls out of scope
#7

Got you!

I almost always do:

local tmp = display.newCircle( group, 10, 10, 10 ) -- 2

It is a habit.

Last question.

Why nil is not required here (as you mentioned above).

I saw so many people doing nil here:

for i = 1, myGroup.numChildren do display.remove (myGroup[i]) end

Thanks Ed!  :slight_smile:

#8

Answer - As long as there are no external references to the objects, simply removing the group and nill-ing any references to the group will be leak-less:

local myGroup = display.newGroup() ... then later display.remove (myGroup) myGroup = nil

Quick FYI, you don’t need to assign nil in the second snippet:

for i = 1, myGroup.numChildren do display.remove (myGroup[i]) end

Please remember to format all code posts.
formatyourcode.jpg

#9

Sorry for not formatting it (it is not easily done while on mobile version).

Can you name one/two examples for  external references to the objects ?

Thanks!

#10

I mean if you have other variables referencing the objects you’re deleting then the objects won’t be garbage collected till those variables are cleared or fall out of scope.

I simply could not assume (in my answer) that you only put the objects in a display group.  I didn’t know if you’d also used variables somewhere to refer to specific objects in that group.

#11

Can you give one simple example?

Word variable is not so clear… 

#12 
local group = display.newGroup() display.newCircle( group, 10, 10, 10 ) -- 1 local tmp = display.newCircle( group, 10, 10, 10 ) -- 2 display.newCircle( group, 10, 10, 10 ) -- 3 display.remove( group ) group = nil -- Circle 1 and 3 are removed and will be garbage collected. -- Circle 2 (referenced by variable 'tmp') is removed, but will not be -- garbage collected till 'tmp' is nilled or falls out of scope
#13

Got you!

I almost always do:

local tmp = display.newCircle( group, 10, 10, 10 ) -- 2

It is a habit.

Last question.

Why nil is not required here (as you mentioned above).

I saw so many people doing nil here:

for i = 1, myGroup.numChildren do display.remove (myGroup[i]) end

Thanks Ed!  :slight_smile: