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You are here: MacNN Forums > Software - Troubleshooting and Discussion > Developer Center > No need to release a newly allocated window?

No need to release a newly allocated window?
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kman42
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Join Date: Sep 2000
Location: San Francisco
Status: Offline
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May 10, 2002, 10:57 AM
 
My understanding of retain/release is that one should try to balance allocations/retains with releases in any block of code. Is this true for new windows as well? I'm having some trouble with the following bit of code:

<BLOCKQUOTE><font size="1"face="Geneva, Verdana, Arial">code:</font><HR><pre><font size=1 face=courier>
-(IBAction)doubleOnSearchResults id)sender {
NSArray *sortedReferenceDictValues;
NSArray *referenceDictValues;
ReferenceController *referenceWindow;
referenceDictValues=[NSArray arrayWithArray:[[currentSearch valueForKey:<font color = orange>@"referenceDictionary"</font>] allValues]];
sortedReferenceDictValues=[referenceDictValues sortedArrayUsingSelector:@selector(compareByYear ];

referenceWindow=[[ReferenceController alloc] initWithReference:[sortedReferenceDictValues objectAtIndex:[searchResults clickedRow]]];
NSLog(<font color = orange>@"A"</font>);

[referenceWindow showWindow:self];
NSLog(<font color = orange>@"b"</font>);

NSLog(<font color = orange>@"d"</font>);
<font color = brown>//[referenceWindow autorelease];</font>
}
</font>[/code]

That last commented line is what is giving me trouble. If I run the app the way it is written above it works fine. The new window opens and stays open. However, if I uncomment that last line (with release or autorelease), the window opens for a flash and then closes. But since I allocated the window in this block of code, don't I want to release it? Should I autorelease it in this code, but add a retain in the init of the new referenceWindow? Would this keep it around and let me balance out my retains/releases?

thanks,
kman
     
Ghoser777
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Join Date: Dec 2000
Location: Chicago, Illinois
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May 10, 2002, 12:18 PM
 
Watch this:

<BLOCKQUOTE><font size="1"face="Geneva, Verdana, Arial">code:</font><HR><pre><font size=1 face=courier>

-(IBAction)object
{
[[[GenericaObject alloc] init] autorelease];
}

</font>[/code]

That's essentially what you've got so far. So, you've got an Object with an initiral retain count of one. This object has it's retain count decremented by one (aka to 0) when we reach the close curly. If you were returning the object, it's good programming form to autorelease it before returning it. In this case, you're just creating an object and dislaying it to the screen, so you shouldn't autorelease it.

HTH,
F-bacher
     
lindberg
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Join Date: Jan 2001
Location: Virginia, US
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May 11, 2002, 05:32 AM
 
You need to [auto]release it eventually if you don't want to leak that memory. However, as you noticed, autorelease gets freed at the end of the current event -- much too soon for you. You need to keep a reference to this window around somehow, and release it when you know you're done with it.

One option would be to have an ivar in the class you're using there, and use it as a "shared" object. i.e.:

<BLOCKQUOTE><font size="1"face="Geneva, Verdana, Arial">code:</font><HR><pre><font size=1 face=courier>
- (void)dealloc
{
...
[referenceWindow release];
[super dealloc];
}

-(IBAction)doubleOnSearchResults id)sender {
NSArray *sortedReferenceDictValues;
NSArray *referenceDictValues;
referenceDictValues=[NSArray arrayWithArray:[[currentSearch valueForKey:<font color = orange>@"referenceDictionary"</font>] allValues]];
sortedReferenceDictValues=[referenceDictValues sortedArrayUsingSelector:@selector(compareByYear ];

if (referenceWindow == nil) {
referenceWindow=[[ReferenceController alloc] init];
}
[referenceWindow setReference:[sortedReferenceDictValues objectAtIndex:[searchResults clickedRow]]];
[referenceWindow showWindow:self];
}
</font>[/code]

Obviously, you can only have one of these reference windows visible at a time with this method.

If you want multiple windows, you could add them to an NSArray you keep as an ivar, and remove it from the array when you get the windowWillClose: delegate method from the corresponding window (you probably want to make sure it's autoreleased instead of released in this case to make sure the object survives to the end of the current event).

If the class in question is an NSDocument and ReferenceController is a subclass of NSWindowController, you could simply add it to the windowControllers array of the document (addWindowController and the releasing details will be taken care of for you.
     
   
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