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Re: revised ownership change [message #32167 is a reply to message #32161]

Thu, 28 April 2011 21:45

Lance is currently offline

Lance
Messages: 527
Registered: March 2007

Contributor

Good job.

Except the template creator should be kept. It's simulating the Array::Create<ChildType>() interface. Look at it this way, a Ctrl is a special type of container: it references some of its children while owning (responsible for their destruction) some others. Since allowing library user to change the owned flag is regarded as unsafe, and use of new/delete by library users is generally discouraged, it makes sense to have a similar Create/Detach interface like does Array.

The point of the template creator (NewChild, AddOwned, CreateOwned or whatever we may choose to call it) is to eliminate the necessity of asking end user to supply a new'ed object, instead of:

    parent.AddOwned(new Button());

now use

    parent.CreateOwned<Button>();
    //
    // similar to 
    // anArray.Create<Button>();
    //

Yes, any access to owned flag should be protected. That's my true intention. Thanks for fixing it.

I still think that to expose Detach to public scope is not a good idea. It should be protected and only accessible through inheritance. Even though it works in common/reasonable senario:

1. a Ctrl is Detached from its parent:
In any case, the Ctrl is removed from its parent's children list. If the Ctrl has owned flag set, a pointer to it will be returned so that user code will be responsible for its eventual destruction; if its a normal stack resident Ctrl. a NULL pointer will be returned to signal the user not to try to delete it afterwards.

2. the user delete's the detached Ctrl after finished using it. No problem, expected scenario.

3. the user decide to add the ctrl to another Ctrl as child by way of Add(), AddChild(), etc. Since the owned flag is correctly set, the new parent will be responsible for its destruction.

So it seems no hole is introduced. But here Add(), AddChild() becomes ambiguous to the user. The user may form an impression that Add()/AddChild() can be supplied with any new'ed Ctrls without the user to worry about their eventual destruction. To avoid this confusion, maybe it's best to simply hide it from library users.

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[Message index]

		Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 17:18
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Wed, 16 March 2011 17:26
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 17:29
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 17:30
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 17:39
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Wed, 16 March 2011 18:01
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 18:10
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 18:29
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 18:35
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 18:43
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 16 March 2011 19:24
		Re: Proposed change to U++ to allow owning children. By: Lance on Fri, 18 March 2011 02:13
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Fri, 18 March 2011 11:01
		Re: Proposed change to U++ to allow owning children. By: Lance on Fri, 18 March 2011 14:39
		Re: Proposed change to U++ to allow owning children. By: Lance on Fri, 18 March 2011 15:21
		Re: Proposed change to U++ to allow owning children. By: Lance on Fri, 18 March 2011 15:40
		Re: Proposed change to U++ to allow owning children. By: Lance on Fri, 18 March 2011 16:22
		Re: Proposed change to U++ to allow owning children. By: Lance on Fri, 18 March 2011 16:34
		Re: Proposed change to U++ to allow owning children. By: mirek on Fri, 18 March 2011 19:35
		Re: Proposed change to U++ to allow owning children. By: mirek on Fri, 18 March 2011 19:32
		Re: Proposed change to U++ to allow owning children. By: Lance on Fri, 18 March 2011 23:02
		Re: Proposed change to U++ to allow owning children. By: mirek on Fri, 18 March 2011 23:18
		Re: Proposed change to U++ to allow owning children. By: Lance on Fri, 18 March 2011 23:34
		Re: Proposed change to U++ to allow owning children. By: mirek on Fri, 18 March 2011 23:40
		Re: Proposed change to U++ to allow owning children. By: Lance on Sat, 19 March 2011 00:02
		Re: Proposed change to U++ to allow owning children. By: mirek on Sat, 19 March 2011 00:37
		Re: Proposed change to U++ to allow owning children. By: Lance on Sat, 19 March 2011 01:30
		Re: Proposed change to U++ to allow owning children. By: Lance on Sat, 19 March 2011 01:35
		Re: Proposed change to U++ to allow owning children. By: mirek on Sat, 19 March 2011 10:59
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Sun, 20 March 2011 10:32
		Re: Proposed change to U++ to allow owning children. By: Lance on Sun, 20 March 2011 14:07
		Re: Proposed change to U++ to allow owning children. By: Lance on Sun, 20 March 2011 14:11
		Re: Proposed change to U++ to allow owning children. By: Lance on Sun, 20 March 2011 14:28
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Fri, 25 March 2011 13:26
		Re: Proposed change to U++ to allow owning children. By: Lance on Sun, 27 March 2011 15:33
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Sun, 17 April 2011 17:25
		Re: Proposed change to U++ to allow owning children. By: Lance on Tue, 19 April 2011 06:00
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Tue, 19 April 2011 09:14
		Re: Proposed change to U++ to allow owning children. By: Lance on Tue, 19 April 2011 14:09
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Tue, 19 April 2011 18:05
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 20 April 2011 02:44
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Wed, 20 April 2011 08:51
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 20 April 2011 19:24
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 20 April 2011 21:17
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 20 April 2011 21:23
		Re: Proposed change to U++ to allow owning children. By: Lance on Wed, 20 April 2011 21:38
		Re: Proposed change to U++ to allow owning children. By: kohait00 on Thu, 28 April 2011 16:32
		revised ownership change By: kohait00 on Thu, 28 April 2011 18:28
		Re: revised ownership change By: Lance on Thu, 28 April 2011 21:45
		Re: revised ownership change By: kohait00 on Thu, 28 April 2011 21:57
		Re: revised ownership change By: Lance on Thu, 28 April 2011 23:18
		Re: revised ownership change By: Lance on Thu, 28 April 2011 23:31
		Re: revised ownership change By: Lance on Thu, 28 April 2011 23:54
		Re: revised ownership change By: kohait00 on Sun, 22 May 2011 21:58
		Re: revised ownership change By: Mindtraveller on Mon, 23 May 2011 00:28
		Re: revised ownership change By: kohait00 on Mon, 23 May 2011 11:16
		Re: revised ownership change By: Lance on Mon, 06 June 2011 05:11
		Re: revised ownership change By: Lance on Mon, 06 June 2011 05:05

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