#import <UIKit/UIKit.h>

@interface UILabel (TextAlign)

@property (nonatomic, assign) BOOL isTop;
@property (nonatomic, assign) BOOL isBottom;

@end

#import "UILabel+TextAlign.h"

@implementation UILabel (TextAlign)

- (void)setIsTop:(BOOL)isTop {
    if (isTop) {
        
        CGSize fontSize = [self.text sizeWithFont:self.font];
        //控制元件的高度除以一行文字的高度
        int num = self.frame.size.height/fontSize.height;
        //計算需要新增換行符個數
        int newLinesToPad = num  - self.numberOfLines;
        self.numberOfLines = 0;
        for(int i=0; i<newLinesToPad; i++)
            //在文字後面新增換行符"/n"
            self.text = [self.text stringByAppendingString:@"\n"];
    }
}

-(void)setIsBottom:(BOOL)isBottom {
    
    if (isBottom) {
        CGSize fontSize = [self.text sizeWithFont:self.font];
        //控制元件的高度除以一行文字的高度
        int num = self.frame.size.height/fontSize.height;
        //計算需要新增換行符個數
        int newLinesToPad = num  - self.numberOfLines;
        self.numberOfLines = 0;
        for(int i=0; i<newLinesToPad; i++)
            //在文字前面新增換行符"/n"
            self.text = [NSString stringWithFormat:@" \n%@",self.text];
    }
}

@end

呼叫方法

self.label.isTop = YES;