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POIPhone autoreleasing a returned NSMutableArray
 

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  1. POIPhone autoreleasing a returned NSMutableArray
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    <p>I'm still relatively new to iPhone development but thought I understood the basic principals of memory management. I have a class method that returns an NSMutableArray, I'm calling alloc and init on the object therefore know I'm responsible for releasing it. However because I'm returning the array I assumed I was supposed to use autorelease when creating the object instead of releasing it.</p> <pre><code>+(NSMutableArray *)getStations:(int)stationType { if(database == nil){ [self openDataBase]; } // Create a temporary array to hold the returned objects NSMutableArray *holder = [[[NSMutableArray alloc] init] autorelease]; // Check if the statement has been defined if(select4 == nil) { const char *sql = "SELECT station_id, station_name, AVG(test_percent) FROM stations LEFT JOIN tests USING (station_id) WHERE station_type = ? GROUP BY station_id ORDER BY station_name ASC"; if(sqlite3_prepare_v2(database, sql, -1, &amp;select4, NULL) != SQLITE_OK){ NSLog(@"Error while creating detail view statement. '%s'", sqlite3_errmsg(database)); } } sqlite3_bind_int(select4, 1, stationType); // Check if the statement executed correctly while(sqlite3_step(select4) == SQLITE_ROW) { NSInteger primaryKey = sqlite3_column_int(select4, 0); Tests *station = [[Tests alloc] initWithPrimaryKey:primaryKey]; station.station_name = [NSString stringWithUTF8String:(char *)sqlite3_column_text(select4, 1)]; station.average_score = [NSNumber numberWithDouble:sqlite3_column_double(select4, 2)]; [holder addObject:station]; [station release]; } // Reset the detail statement. sqlite3_reset(select4); // Return the holder array return holder; } </code></pre> <p>There's the basic code - XCode no longer indicates a potential memory leak but it crashes everytime that code executes saying message sent to deallocated instance. Any help would be appreciated I've spent ages googling and can't see what's wrong with the code. I did find this thread but it doesn't appear to be the answer to my question - <a href="https://stackoverflow.com/questions/2452959/crash-happens-when-nsmutablearray-is-returned">crash happens when NSMutableArray is returned?</a></p>
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    1. USStuart Bates
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    1. COIt crashes inside this method or after this method?
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      1. USTerry Wilcox
    2. COTell us about the crash -- where does it happen and what error message is displayed in the console? What does the code calling this method look like?
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      1. USCaleb
    3. COAfter this method, when the table view calls count on the returned array - but if I remove autorelease it works fine (except for the 'potential memory leak' warning. The error message is: -[__NSArrayM count]: message sent to deallocated instance 0x5d75a00
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      1. USStuart Bates
 

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