Re: newbie EXC_BAD_ACCESS
Re: newbie EXC_BAD_ACCESS
- Subject: Re: newbie EXC_BAD_ACCESS
- From: Daniel Child <email@hidden>
- Date: Mon, 21 Mar 2005 15:56:58 -1000
On Monday, March 21, 2005, at 02:35 PM, Hamish Allan wrote:
NSString **descPtr = &desc;
while (![scanner isAtEnd) {
sd = [[StrokeDescription alloc] init];
BOOL foundType = [scanner scanInt: typePtr];
BOOL foundDesc = [scanner scanUpToString:@"\n" intoString:descPtr];
if (foundType && foundDesc).
[sd setStrokeType: type];
[sd setStrokeDesc: desc];
[self addStrokeDesc: sd]; // to add to knownStrokes array
// where addStrokeDesc retains the passed parameter sd
[sd release];
Aargh! Why have you changed the autorelease I handed you on a plate, into a release?!
I am trying to accomplish the same thing using the private accessors I originally had. Here's how I think it works....
while looping in progress
allocate memory for sd (sd retainCount = 1)
scan the info
set the instance variables type and desc
add sd to knownStrokes (via the addStrokeDesc method)
(sd retainCount = 2)
release sd (retainCount = 1)
My biggest surprise in your solution was the use of + for a class method. Kochan doesn't seem to do that much in his examples, so it never occurred to me to try. Maybe the real question I need to ask is:
- When should I go for a class method as opposed to instance method? In other words, is there some significant difference between your approach:
+ (int)type desc:(NSString *)desc
..... return [sd autorelease]
and something like
- (id)initStrokeDescriptionWithType:(int)type desc:(NSString *)desc
..... return [self autorelease] // or just return self ???
The calls would look different, but I don't see pluses or minuses either way. When to use one over the other?
I guess this relates to my earlier question: the articles repeatedly explain when to use release/autorelease (when you have used alloc/init/copy), but they don't explain when it is preferable to use alloc/init over some other approach, or in this case, a class vs instance method (when both could work).
In other words, without using a public constructor and sticking with plain old instance accessors, can you create the sd's and then place them in the array? Once sigdev error was solved, I was having troubles because the knownStrokes array was getting the last copy of sd created placed in every single slot of the array.
That's because you changed the autorelease to a release.
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