UILabel居上对齐居下对齐类别扩展

@interface UILabel(VerticalAlign)
-(void)alignTop;
-(void)alignBottom;
@end

@implementation UILabel(VerticalAlign)
-(void)alignTop {
CGSize fontSize =[self.text sizeWithFont:self.font];
double finalHeight = self.frame.size.height;//fontSize.height *self.numberOfLines;
double finalWidth =self.frame.size.width;//expected width of label
CGSize theStringSize =[self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
int newLinesToPad =(finalHeight - theStringSize.height)/ fontSize.height;
for(int i=0; i<newLinesToPad; i++)
self.text =[self.text stringByAppendingString:@"\n "];
}

-(void)alignBottom {
CGSize fontSize =[self.text sizeWithFont:self.font];
double finalHeight = fontSize.height *self.numberOfLines;
double finalWidth =self.frame.size.width;//expected width of label
CGSize theStringSize =[self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
int newLinesToPad =(finalHeight - theStringSize.height)/ fontSize.height;
for(int i=0; i<newLinesToPad; i++)
self.text =[NSString stringWithFormat:@" \n%@",self.text];
}
@end