UILabel顶端对齐

比较一劳永逸的写法是对label添加一个分类

@interface UILabel (VerticalAlign)
/** 顶端对齐 */
-(void)alignTop;
/** 底部对齐 */
-(void)alignBottom;
@end

-(void)alignTop{
    CGSize fontSize = [self.text sizeWithAttributes:@{NSFontAttributeName:self.font}];
    double finalHeight = fontSize.height * self.numberOfLines;
    double finalWidth = self.frame.size.width;
    CGSize theStringSize = [self.text boundingRectWithSize:CGSizeMake(finalWidth, finalHeight)
                                                   options:NSStringDrawingUsesLineFragmentOrigin
                                                attributes:@{NSFontAttributeName:self.font}
                                                   context:nil].size;
    int newLinesToPad = (finalHeight - theStringSize.height) / fontSize.height;
    for(int i=0; i<newLinesToPad; i++){
        self.text = [self.text stringByAppendingString:@"
 "];
    }
}

-(void)alignBottom{
    CGSize fontSize = [self.text sizeWithAttributes:@{NSFontAttributeName:self.font}];
    double finalHeight = fontSize.height * self.numberOfLines;
    double finalWidth = self.frame.size.width;
    CGSize theStringSize = [self.text boundingRectWithSize:CGSizeMake(finalWidth, finalHeight)
                                                   options:NSStringDrawingUsesLineFragmentOrigin
                                                attributes:@{NSFontAttributeName:self.font}
                                                   context:nil].size;
    int newLinesToPad = (finalHeight - theStringSize.height) / fontSize.height;
    for(int i=0; i<newLinesToPad; i++){
        self.text = [NSString stringWithFormat:@" 
%@",self.text];
    }
}

然后在使用时添加[myLabel alignTop]即可。
添加前

使用后