swift 对时间的比较处理 【转载XMG】

开发过程中经常会遇见需要对时间进行处理或者比较，以下为微博显示时间的时间比较，重点是当超过一天的时间比较，采用了Calendar（日历）类中的一些方法来处理，比较实用

    /// 比较传入的字符串时间和当前时间
    ///
    /// - Parameter createdAT: 字符串时间
    /// - Returns: 比较结果
    static func creatDateFromString(createdAT : String) -> String {
        let fmt = DateFormatter()
        
        fmt.dateFormat = "EEE MM dd HH:mm:ss Z yyyy"
        fmt.locale = Locale.init(identifier: "en")
        
        guard let createdDate = fmt.date(from: createdAT) else {
            return ""
        }
        
        let currentDate = Date()
        let interval = currentDate.timeIntervalSince(createdDate)
        
        if interval < 60 {
            return "刚刚"
        }
        
        if interval < 60 * 60 {
            let m = String(format: "%.0f", interval / 60)
            return "\(m)分钟前"
        }
        
        if interval < 60 * 60 * 24 {
            let m = String(format: "%.0f", interval / (60 * 60))
            return "\(m)小时前"
        }
        
        // 日历
        let calendar = Calendar.current
        if calendar.isDateInYesterday(createdDate) {
            fmt.dateFormat = "昨天 HH:mm"
            let dateStr = fmt.string(from: createdDate)
            return dateStr
        }
        
        let cmps = calendar.dateComponents([.year], from: createdDate, to: currentDate)
        if cmps.year! < 1 {
            fmt.dateFormat = "MM-dd HH:mm"
            let dateStr = fmt.string(from: createdDate)
            return dateStr
        }
        
        
        fmt.dateFormat = "yyyy-MM-dd HH:mm"
        let dateStr = fmt.string(from: createdDate)
        return dateStr
    }