如何向NSMutableArray中添加一个整数值?

NSMutableArray * val;
val = [[NSMutableArray alloc] initWithCapacity:15];

/*int outlineWidth = barOutlineWidth;
int outlineHalfWidth = (outlineWidth > 1) ? outlineWidth * 0.5f : 0;
 */
for ( Bar * obj in values )
{  
  // calcualte the bar size
  float value  = [obj value];
  float scale  = ( value / maxValue );

  // shift the bar to the top or bottom of the render line
  int pointY   = lineHeight + ( (lineWidth * 0.5f) * ( ( value >= 0.0f ) ? -1 : 1 ) );
  int barHeight = height * scale;
  NSLog(@"%d", barHeight);   
  CGRect barRect = CGRectMake(pointX, pointY, width, -barHeight);
  [val addObject:[NSNumber numberWithInt:barHeight]];
                     NSLog(@"%d", val);
NSMutableArray * val;
val = [[NSMutableArray al