retain

• Mike Manzano retain Apr 11 2001, 21:23
  Thanks to everyone who responded to my question, re: Best time to
  init UI elements.  Overloading awakeFromNib worked beautifully.  And
  now, another question:
  
  If I do this:
  
    [thePreviewBox setImage:_previewImage] ;
  
  can I assume that thePreviewBox will retain _previewImage
  automatically, or must I do that myself?  Can I always assume that a
  receiver passed an object will retain?
  
  Forgive the question if it sounds stupid, I come from a C++
  background :)
  
  m i k e  m a n z a n o
  <lynx...>
  206.674.3277
  
  "It's a shame when whole families are torn apart by something as
  simple as wild dogs."
• mmalcolm crawford Re: retain Apr 11 2001, 21:44
  Mike Manzano wrote:
  
  

  > If I do this:
  > [thePreviewBox setImage:_previewImage] ;
  > can I assume that thePreviewBox will retain _previewImage
  > automatically, or must I do that myself?  Can I always assume that a
  > receiver passed an object will retain?
  >
  

  Yes.  You should only take care of your own memory management, and you
  should assume that the other objects play by the same rules.
  
  If you're creating the preview image locally you should have either:
  
  _previewImage = [[NSImage alloc] init...];
  // ...
  [thePreviewBox setImage:_previewImage] ;
  [_previewImage release];
  or
  _previewImage = [NSImage imageUsingConvenienceConstructorMethod];
  [thePreviewBox setImage:_previewImage] ;
  
  and that's it (objects created using convenience constructors are
  assumed to be autoreleased).
  
  See a forthcoming article on the subject at Stepwise for a set of simple
  rules and examples; for a detailed analysis for now see:
  
  http://www.stepwise.com/Articles/Technical/HoldMe.html
  
  mmalc.
• mmalcolm crawford Re: retain Apr 12 2001, 16:22
  I wrote:
  

  > See a forthcoming article on the subject at Stepwise for a set of simple
  > rules and examples
  

  
  Now at:
  http://www.stepwise.com/Articles/Technical/2001-03-11.01.html
  
  Thank you to those who have sent feedback already.  I do intend to ad a
  "drilldown" piece on "set" accessor methods to elaborate on the
  different issues there.  The intention of the first article is to keep
  things as simple as possible at the outset, and I didn't want to
  complicate things with a discussion of when to copy, autorelease etc.
  variables.
  
  mmalc.