So, you are saying I should call a retain when I get my reference so that it is
kept as an instance var?
On 27 Mar 2010, at 19:33, Sandor Szatmari wrote:
> Every time this method runs you would loose the reference to the memory
> previously allocated for the fields array. This happens when you assign a
> newly allocated array to feilds.
>
> You should either release fields before reassigning it (conditionally if it
> is not nil), or do not reallocate memory for it, instead empty it and reuse
> the existing memory.
>
> Sandor Szatmari
>
> On Mar 27, 2010, at 15:06, Michael Davey <frak....@gmail.com> wrote:
>
>> Hi!
>>
>> I have been running my iPhone application through the Leaks Instrument in an
>> attempt to further understand what I have been coding, however, I fear I do
>> not know enough about how retain/release work to be able to fix my leaks,
>> and I was wondering if I could paste one trouble spot function that I have
>> identified, and if someone could be so kind as to point out how I can fix
>> the leaks and how to code them out in the future?
>>
>> My function returns a row from a SQLite database as an NSDictionary, and is
>> as follows:
>>
>> -(NSDictionary *)fetch {
>> NSMutableDictionary *output = nil;
>> if (db != nil && sth != nil) {
>> int c = sqlite3_column_count(sth);
>> if (fields == nil) {
>> fields = [[NSMutableArray alloc] init];
>> for (int i = 0; i < c; ++i) {
>> const char *name = sqlite3_column_name(sth, i);
>> [fields addObject:[NSString stringWithUTF8String:name]];
>> }
>> }
>> if (sqlite3_step(sth) == SQLITE_ROW) {
>> output = [[[NSMutableDictionary alloc] init] autorelease];
>> for (int i = 0; i < c; ++i) {
>> const unsigned char *val = sqlite3_column_text(sth, i);
>> NSString *value;
>> if (val == nil) {
>> value = @"{NULL}";
>> }
>> else {
>> value = [NSString stringWithUTF8String:(char *)val];
>> }
>> [output setObject:value forKey:[fields objectAtIndex:i]];
>> }
>> }
>> }
>> return output;
>> }
>>
>> The first leak reported by instruments is on the line where I alloc and init
>> fields as an NSMutable array. Firstly, fields is declared in my header, and
>> is released in my dealloc method, so I am unsure what I have missed here and
>> would be glad for any pointers on this problem.
>>
>> The second is reported in the following line:
>>
>> [fields addObject:[NSString stringWithUTF8String:name]];
>>
>> Now, I can see that there is an anonymous string being created, but I am
>> totally unsure as to how I can avoid leaking memory right here?
>>
>> The third leak reported is here:
>>
>> output = [[[NSMutableDictionary alloc] init] autorelease];
>>
>> Now, I thought by using autorelease I was able to sidestep the issue of
>> releasing this object (and I am pretty sure that adding this help fix an
>> error that clang reported - could this be a false positive?)
>>
>> And the last error is where I create the NSString value from the char *val -
>> I believe this to be a similar class of error as my second leak, and would
>> probably be addressed in a similar fashion.
>>
>> So, sorry for such a lengthy email, and for asking so much of someone's
>> time, but I hope that by seeing where I am going wrong here, I will be able
>> to adopt good practices early on and make my code more robust in the future.
>>
>> Many thanks to the poor soul who has to teach me the error of my ways in
>> advance :o)
>>
>> Mikey_______________________________________________
>>
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