iOS Swift之时间段抓取

在家手痒就给自己找了点事做做，下面是关于怎么获取某个时间点对应时间段的一些方法，包含本周（上周，下周）开始结束日期，本月（上月，下月）开始结束日期，本年（上年，下年）开始结束日期的获取方法。内容以后会持续更新：
（封装在一个自定义的类中（DateEncapsulation））
指定日期的当前周，上周，下周 的时间段

// MARK: - week
static func getThisWeek(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd"
        
        let calendar = Calendar.current
        let comp = calendar.dateComponents([.year, .month, .day, .weekday], from: date)
        
        // 获取今天是周几, 今天是几号
        if let weekDay = comp.weekday, let day = comp.day {
            
            // 计算当前日期和本周的星期一和星期天相差天数
            var firstDiff: Int
            var lastDiff: Int
            // weekDay = 1;
            if (weekDay == 1) {
                firstDiff = -6;
                lastDiff = 0;
            } else {
                firstDiff = calendar.firstWeekday - weekDay + 1
                lastDiff = 8 - weekDay
            }
            
            // 在当前日期(去掉时分秒)基础上加上差的天数
            var firstDayComp = calendar.dateComponents([.year, .month, .day], from: date)
            firstDayComp.day = day + firstDiff
            var lastDayComp = calendar.dateComponents([.year, .month, .day], from: date)
            lastDayComp.day = day + lastDiff
            
            if let firstDayOfWeek = calendar.date(from: firstDayComp), let lastDayOfWeek = calendar.date(from: lastDayComp) {
                
                let firstDay = dateFormatter.string(from: firstDayOfWeek)
                let lastDay = dateFormatter.string(from: lastDayOfWeek)
                
                return (firstDate: firstDay, lastDate: lastDay)
            }
        }
       return nil
    }

 static func getLastWeek(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
         dateFormatter.dateFormat = "yyyy-MM-dd"
        
         let calendar = Calendar.current
         let comp = calendar.dateComponents([.year, .month, .day, .weekday], from: date)
         
         // 获取今天是周几, 今天是几号
         if let weekDay = comp.weekday, let day = comp.day {
             
             // 计算当前日期和本周的星期一和星期天相差天数
             var firstDiff: Int
             var lastDiff: Int
             // weekDay = 1;
             if (weekDay == 1) {
                 firstDiff = -6;
                 lastDiff = 0;
             } else {
                 firstDiff = calendar.firstWeekday - weekDay + 1
                 lastDiff = 8 - weekDay
             }

            // 上周，减七天
            firstDiff -= 7
            lastDiff -= 7
             
             // 在当前日期(去掉时分秒)基础上加上差的天数
             var firstDayComp = calendar.dateComponents([.year, .month, .day], from: date)
             firstDayComp.day = day + firstDiff
             var lastDayComp = calendar.dateComponents([.year, .month, .day], from: date)
             lastDayComp.day = day + lastDiff
             
             if let firstDayOfWeek = calendar.date(from: firstDayComp), let lastDayOfWeek = calendar.date(from: lastDayComp) {
                 
                 let firstDay = dateFormatter.string(from: firstDayOfWeek)
                 let lastDay = dateFormatter.string(from: lastDayOfWeek)
                 
                 return (firstDate: firstDay, lastDate: lastDay)
             }
         }
         
        return nil
    }
    
    static func getNextWeek(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
         dateFormatter.dateFormat = "yyyy-MM-dd"
        
         let calendar = Calendar.current
         let comp = calendar.dateComponents([.year, .month, .day, .weekday], from: date)
         
         // 获取今天是周几, 今天是几号
         if let weekDay = comp.weekday, let day = comp.day {
             
             // 计算当前日期和本周的星期一和星期天相差天数
             var firstDiff: Int
             var lastDiff: Int
             // weekDay = 1;
             if (weekDay == 1) {
                 firstDiff = -6;
                 lastDiff = 0;
             } else {
                 firstDiff = calendar.firstWeekday - weekDay + 1
                 lastDiff = 8 - weekDay
             }

            // 下周，加七天
            firstDiff += 7
            lastDiff += 7
             
             // 在当前日期(去掉时分秒)基础上加上差的天数
             var firstDayComp = calendar.dateComponents([.year, .month, .day], from: date)
             firstDayComp.day = day + firstDiff
             var lastDayComp = calendar.dateComponents([.year, .month, .day], from: date)
             lastDayComp.day = day + lastDiff
             
             if let firstDayOfWeek = calendar.date(from: firstDayComp), let lastDayOfWeek = calendar.date(from: lastDayComp) {
                 
                 let firstDay = dateFormatter.string(from: firstDayOfWeek)
                 let lastDay = dateFormatter.string(from: lastDayOfWeek)
                 
                 return (firstDate: firstDay, lastDate: lastDay)
             }
         }
        return nil
    }

指定日期的当前月，上月，下月 的时间段

// MARK: - month
static func getThisMonth(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd"
        
        let calendar = Calendar.current
        let currentComponents = calendar.dateComponents([.year, .month], from: date)
        
        if let startDate = calendar.date(from: currentComponents) {
            // 当月第一天
            let startDayString = dateFormatter.string(from: startDate)
            
            var diffComponents = DateComponents()
            // 比当月一日多一个月少一天即为当月最后一日
            diffComponents.month = 1
            diffComponents.day = -1
            if let endDate = calendar.date(byAdding: diffComponents, to: startDate) {
                let endDayString = dateFormatter.string(from: endDate)
                return (firstDate: startDayString, lastDate: endDayString)
            }
        }
        
        return nil
    }
    
    static func getLastMonth(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd"
        
        // 当前传入日期 转成 Date 格式
        let calendar = Calendar.current
        var currentComponents = calendar.dateComponents([.year, .month, .day], from: date)
        
        // 设置为 1，转成 Date 后为当前传入日期月份的第一天
        currentComponents.day = 1
        
        if let startOfMonth = calendar.date(from: currentComponents) {
            
            var diffComponents = DateComponents()
            // 比当前月一日少一个月即为上月一日
            diffComponents.month = -1
            
            // 当月第一天
            if let startDate = calendar.date(byAdding: diffComponents, to: startOfMonth) {
                let startDayString = dateFormatter.string(from: startDate)
                
                // 比当前月少一天即为上月最后一日
                diffComponents.month = 0
                diffComponents.day = -1
                if let endDate = calendar.date(byAdding: diffComponents, to: startOfMonth) {
                    let endDayString = dateFormatter.string(from: endDate)
                    return (firstDate: startDayString, lastDate: endDayString)
                }
            }
        }
        return nil
    }
    
    static func getNextMonth(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd"
        
        let calendar = Calendar.current
        
        // 当前传入日期 转成 DateComponents 格式
        var currentComponents = calendar.dateComponents([.year, .month, .day], from: date)
        
        // 设置为 1，转成 Date 后为当前传入日期月份的第一天
        currentComponents.day = 1
        
        if let startOfMonth = calendar.date(from: currentComponents) {
                        
            // 处理时间差
            var diffComponents = DateComponents()
            // 添加一个月的时间差
            diffComponents.month = 1
            
            // 下个月第一天
            if let startDate = calendar.date(byAdding: diffComponents, to: startOfMonth) {
                let startDayString = dateFormatter.string(from: startDate)
                
                // 和当前月第一天相差两个月少一天即为下个月最后一天时间
                diffComponents.month = 2
                diffComponents.day = -1
                if let endDate = calendar.date(byAdding: diffComponents, to: startOfMonth) {
                    let endDayString = dateFormatter.string(from: endDate)
                    return (firstDate: startDayString, lastDate: endDayString)
                }
            }
        }
        return nil
    }

指定日期的当前年，上一年，下一年 的时间段

 // MARK: - year
    static func getThisYear(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd"
        
        let calendar = Calendar.current
        let currentComponents = calendar.dateComponents([.year], from: date)
        if let startDate = calendar.date(from: currentComponents) {
            // 当年第一天
            let startDayString = dateFormatter.string(from: startDate)
            
            var diffComponents = DateComponents()
            // 比当年一月一号多一年少一天即为当年最后一日
            diffComponents.year = 1
            diffComponents.day = -1
            if let endDate = calendar.date(byAdding: diffComponents, to: startDate) {
                let endDayString = dateFormatter.string(from: endDate)
                return (firstDate: startDayString, lastDate: endDayString)
            }
        }
        return nil
    }

    static func getLastYear(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd"
        
        let calendar = Calendar.current
        let currentComponents = calendar.dateComponents([.year], from: date)
        if let startDate = calendar.date(from: currentComponents) {
            // 当年第一天
            // let startOfday = dateFormatter.string(from: startOfMonth)
            
            var diffComponents = DateComponents()
            
            diffComponents.year = -1
            if let startOfLastYear = calendar.date(byAdding: diffComponents, to: startDate) {
                let startDayString = dateFormatter.string(from: startOfLastYear)
                
                // 比当年一月一号多一年少一天即为当年最后一日
                diffComponents.year = 0
                diffComponents.day = -1
                if let endDate = calendar.date(byAdding: diffComponents, to: startDate) {
                    let endDayString = dateFormatter.string(from: endDate)
                    return (firstDate: startDayString, lastDate: endDayString)
                }
                
            }
            
        }
        return nil
    }

    static func getNextYear(_ date: Date) -> (firstDate: String, lastDate: String)? {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd"
        
        let calendar = Calendar.current
        let currentComponents = calendar.dateComponents([.year], from: date)
        if let startOfMonth = calendar.date(from: currentComponents) {
            // 当年第一天
            // let startOfday = dateFormatter.string(from: startOfMonth)
            
            var diffComponents = DateComponents()
            
            diffComponents.year = 1
            if let startDate = calendar.date(byAdding: diffComponents, to: startOfMonth) {
                let startDayString = dateFormatter.string(from: startDate)
                
                // 比当年一月一号多一年少一天即为当年最后一日
                diffComponents.year = 2
                diffComponents.day = -1
                if let endDate = calendar.date(byAdding: diffComponents, to: startOfMonth) {
                    let endDayString = dateFormatter.string(from: endDate)
                    return (firstDate: startDayString, lastDate: endDayString)
                }
                
            }
            
        }
        return nil
    }

为了方便获取，又做了一些集中处理，加了两个枚举类型

// 周/月/年
    enum CalendarFormMode {
        case week
        case month
        case year
    }

    // 上周/月/年， 本周/月/年， 下周/月/年
    enum CalendarSequence {
        case this(CalendarFormMode)
        case last(CalendarFormMode)
        case next(CalendarFormMode)
    }

// 通过输入 enum 获取 对应时间的 时间段
    class func dateSpanFromDate(_ date: Date, mode: DateEncapsulation.CalendarSequence) -> (firstDate: String, lastDate: String)? {
        switch mode {
        case .this(.week):
            return DateEncapsulation.getThisWeek(date)
        case .this(.month):
            return DateEncapsulation.getThisMonth(date)
        case .this(.year):
            return DateEncapsulation.getThisYear(date)
        case .last(.week):
            return DateEncapsulation.getLastWeek(date)
        case .last(.month):
            return DateEncapsulation.getLastMonth(date)
        case .last(.year):
            return DateEncapsulation.getLastYear(date)
        case .next(.week):
            return DateEncapsulation.getNextWeek(date)
        case .next(.month):
            return DateEncapsulation.getNextMonth(date)
        case .next(.year):
            return DateEncapsulation.getNextYear(date)
        }
    }

exp:

DateEncapsulation.dateSpanFromDate(Date(), mode: .this(.week))