Question

I’ve been using the following code without almost any problems, but today Xcode begun to complain about it BIGTIME. I almost went nuts before I could find were the bug/memory leak indeed was. Xcode said “message sent to deallocated instance”. I commented a couple of lines (the releases) and it stopped crashing.

The thing is, I’m completely lost here… shouldn’t I release those to avoid memory leaks? I’m targeting iOS 4.0 for this project, so manual memory managment is a must.

+ (NSString*)reformatRule:(NSString*) ruleStr {
    NSString *bufRule = [[[NSString alloc] init] autorelease];
    NSString *buf = [[NSString alloc] init];
    char c = 0;
    NSString *value = [[NSString alloc] init];
    for(int i=0;i<[ruleStr length];i++){
        c = [ruleStr characterAtIndex:i];
        if([self isCharacterOrDigit:[NSString stringWithFormat:@"%c",c]]){
            buf = [buf stringByAppendingString:[NSString stringWithFormat:@"%c",c]];
        }else{
            DLog(@"says:%@",buf);
            value = [buf stringByReplacingOccurrencesOfString:@" " withString:@""];
            //[buf release];
            //buf = [[NSString alloc] init];
            buf = @"";
            if (![value isEqualToString:@""]) {
                if ([value isEqualToString:CONDITION_AND] || [value isEqualToString:CONDITION_OR]) {
                    bufRule = [bufRule stringByAppendingString:[NSString stringWithFormat:@"%@",value]];
                }else{
                    bufRule = [bufRule stringByAppendingString:[NSString stringWithFormat:@"(%@)",value]];
                }
            }

            if(c!=' '){
            bufRule = [bufRule stringByAppendingString:[NSString stringWithFormat:@"%c",c]];
            }
        }
    }

    // [value release]; COMMENTED THIS LINE
    // [buf release]; AND THIS ONE TOO
    return bufRule;
}

Answer 1

This line converts buf from a retained pointer to an autoretained one:

buf = [buf stringByAppendingString:[NSString stringWithFormat:@"%c",c]];

Similarly the value line a couple of lines down.

If you’re not going to use ARC, you really need to understand storage management a lot better.