Question

This is a common case:
In code below (simplified), number of the dictionaries added to the array varies depending on size of data set (as usual).
So it is impossible to match each dictionary with a corresponding ‘release’ statement.
I assume releasing the array (in dealloc) would release all its enclosed dictionaries?
Nevertheless, it produces a leak. How to eliminate it?

// -----myController.h----
@interface ExerciseGraphController : UIViewController <CPPlotDataSource>{        
    NSMutableArray          *plotDataForBar;
}
@property(readwrite, retain, nonatomic)NSMutableArray *plotDataForBar;                  

// -----myController.m----
- ...getPlotData... {

        //Solution
        if (plotDataForBar){
            [plotDataForBar  release];
        }

        plotDataForBar = [[NSMutableArray array] init];                             

        //for each item in plotDataForBar {                      
            ...                                         //Populates plotDataForBar with dictionaries.
            [plotDataForBar addObject:   [NSDictionary dictionaryWithObjectsAndKeys:     // **LEAK** ( on __NSCFDictionary, __NSArrayM, and _GeneralBlock16)
                [NSDecimalNumber numberWithFloat:xF], [NSNumber numberWithInt:CPBarPlotFieldBarLocation],    
                [NSDecimalNumber numberWithFloat:yF], [NSNumber numberWithInt:CPBarPlotFieldBarLength],  
                nil]];
        }                                                            
}                                                       //Reads plotDataForBar in:
- ...numberOfRecordsForPlot...{                         //      Method required by CorePlot 
    return  [plotDataForBar count];     
}           
- ...numberForPlot... {                                 //      "       "     "      "  
    ... 
    NSDecimalNumber *num = [[plotDataForBar objectAtIndex:index] objectForKey:[NSNumber numberWithInt:fieldEnum]];
    ...     
 }
- ...dealloc  { 
    [plotDataForBar release]; 
    [super dealloc]; 
}

Answer 1

As much code is missing, only a guess:

Shouldn’t you test in “…getPlotData…” if that property is already set, or release the old instance? This would be leaking every time this method gets called.