根据日期计算星座

在app中，展示个人信息时，有时候服务器只返回一个生日，然后要在个人信息里展示相应的星座名称和图标，这时候就需要客户端根据生日自己计算，那么怎么计算呢，方法很简单。

1. 申明一个星座结构体，里面包含星座code，星座名字。
   code用来标识一个星座，可以根据code来设置不同的星座图片，在需要国际化的时候根据code来展示相应的本地化字符串。

struct JPSConstellation {
    ///星座code
    var code: Int
    ///星座名
    var name: String
}

2. 根据日期计算出星座

func constellationWith(date: Date) -> JPSConstellation? {
        guard let calendar = NSCalendar(identifier: NSCalendar.Identifier.gregorian) else {
            return nil
        }
        let components = calendar.components([.month, .day], from: date)
        let month = components.month!
        let day = components.day!
        
        
        // 月以100倍之月作为一个数字计算出来
        let mmdd = month * 100 + day;
        var constellation: JPSConstellation?
        
        if ((mmdd >= 321 && mmdd <= 331) ||
            (mmdd >= 401 && mmdd <= 419)) {
            constellation = JPSConstellation(code: 1, name: "白羊座")
            
        } else if ((mmdd >= 420 && mmdd <= 430) ||
            (mmdd >= 501 && mmdd <= 520)) {
            constellation = JPSConstellation(code: 2, name: "金牛座")
            
        } else if ((mmdd >= 521 && mmdd <= 531) ||
            (mmdd >= 601 && mmdd <= 621)) {
            constellation = JPSConstellation(code: 3, name: "双子座")
            
        } else if ((mmdd >= 622 && mmdd <= 630) ||
            (mmdd >= 701 && mmdd <= 722)) {
            constellation = JPSConstellation(code: 4, name: "巨蟹座")
            
        } else if ((mmdd >= 723 && mmdd <= 731) ||
            (mmdd >= 801 && mmdd <= 822)) {
            constellation = JPSConstellation(code: 5, name: "狮子座")
            
        } else if ((mmdd >= 823 && mmdd <= 831) ||
            (mmdd >= 901 && mmdd <= 922)) {
            constellation = JPSConstellation(code: 6, name: "处女座")
            
        } else if ((mmdd >= 923 && mmdd <= 930) ||
            (mmdd >= 1001 && mmdd <= 1023)) {
            constellation = JPSConstellation(code: 7, name: "天秤座")
            
        } else if ((mmdd >= 1024 && mmdd <= 1031) ||
            (mmdd >= 1101 && mmdd <= 1122)) {
            constellation = JPSConstellation(code: 8, name: "天蝎座")
            
        } else if ((mmdd >= 1123 && mmdd <= 1130) ||
            (mmdd >= 1201 && mmdd <= 1221)) {
            constellation = JPSConstellation(code: 9, name: "射手座")
            
        } else if ((mmdd >= 1222 && mmdd <= 1231) ||
            (mmdd >= 101 && mmdd <= 119)) {
            constellation = JPSConstellation(code: 10, name: "摩羯座")
            
        } else if ((mmdd >= 120 && mmdd <= 131) ||
            (mmdd >= 201 && mmdd <= 218)) {
            constellation = JPSConstellation(code: 11, name: "水瓶座")
            
        } else if ((mmdd >= 219 && mmdd <= 229) ||
            (mmdd >= 301 && mmdd <= 320)) {
            //考虑到2月闰年有29天的
            constellation = JPSConstellation(code: 12, name: "双鱼座")
            
        }else{
            print(mmdd)
            print("日期错误")
            constellation = nil
        }
        return constellation
    }

3. 最后可以打印验证一下

override func viewDidLoad() {
        super.viewDidLoad()
        
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy/MM/dd"
        let date = formatter.date(from: "1995/1/11")
  
        let constellation = constellationWith(date: date!)
        print(constellation?.name as Any)
}