UITextField添加图片以及文字居中

最右侧加图片是以下代码:
    UIImageView *img = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"right.png"]]; text.rightView = img; text.rightViewMode = UITextFieldViewModeAlways;   
如果是在最左侧加图片就换成:
text.leftView = img; text.leftViewMode = UITextFieldViewModeAlways;   
UITextField 继承自 UIControl,此类中有一个属性contentVerticalAlignment
所以想让UITextField里面的text垂直居中可以这样写:
text.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;