How to set up a VNCoreMLRequest with VNRequestCompletitionHandler

VNCoreMLRequest.m

 VNCoreMLRequest *request = [[VNCoreMLRequest alloc] initWithModel: vnc_core_ml_model completionHandler: (VNRequestCompletionHandler) ^(VNRequest *request, NSError *error){
        NSArray *results = [request.results copy];
        
        VNCoreMLFeatureValueObservation *res = ((VNCoreMLFeatureValueObservation *)(results[0]));
        
        NSNumber *prediction = [NSNumber numberWithFloat:0];
        NSNumber *compare= [NSNumber numberWithFloat:0];
        int atIndex = 0;
        
        
        for(int i = 0; i<[res.featureValue multiArrayValue].count; i++){
            
            compare = [[res.featureValue multiArrayValue] objectAtIndexedSubscript:i];
            if([compare floatValue] > [prediction floatValue]){
                prediction = compare;
                atIndex = i;
            }
        }
        
       // double predictionPercentage = [[[res.featureValue multiArrayValue] objectAtIndexedSubscript:atIndex] doubleValue];
        
        NSString *result = @"";
        self.resultLabel.text = [result stringByAppendingFormat: @"Digit may be: %i", atIndex];
    }];