drawRect：rect如何调用此方法，我用来绘制一个字符串

-(void)drawRect:(CGRect)rect
{   
    CGContextRef  context = UIGraphicsGetCurrentContext();
    CGContextSelectFont(context, "Arial", 24, kCGEncodingFontSpecific);
    CGContextSetTextPosition(context,80,80);
    CGContextShowText(context, "hello", 6);
    //not even this works
    CGContextShowTextAtPoint(context, 1,1, "hello", 6);
}
-(void)drawRect:(CGRect)rect
{   
    CGContext