NSAttributedString

        1.//加载图片
        NSTextAttachment *attch = [[NSTextAttachment alloc] init];
        attch.image = [UIImage imageNamed:emotion.png];
        CGFloat attchWH = self.font.lineHeight;
        attch.bounds = CGRectMake(0, -4, attchWH, attchWH);
        //根据附件创建一个属性文字
        NSAttributedString *imageStr = [NSAttributedString attributedStringWithAttachment:attch];
        
        2.//拼接文字
        [attributedText appendAttributedString:self.attributedText];
        
        3.//NSAttributedString转化为NSString
        NSString *str = attributedText.string