如何跟踪随日期变化的数据？

Question

I have a school app that keeps track of your schedule. The app has a multitude of options for inputting the schedule. If the user has a four day schedule, then they will have AD days. For my app. I'd like to keep track of what the current day is (for instance, whether or not it is an A day vs. a C day). The user will be able to specify what day it is when they set up the app, but then the app should keep track of this change day to day, minus weekends. I'm not sure what the best way to implement this is.

Answer 1

If the configuration allows completely arbitrary day assignments, you would only need a simple dictionary in the form [Date:String].

If you want to let your users specify repeating patterns of day identifiers (letters), the configuration parameters and process will need to be more sophisticated and will depend on how far you're willing to go in processing exceptions (ie non school days). Weekends can be automatic but holidays and scheduled "off days" would require that you define some kind of rule (hard coded or user configurable).

In all cases, I would suggest creating a function that converts any date into its day identifier based on the configured parameters. Depending on the complexity of the rules and the range of dates you are working with, it may be a good idea to dynamically build a global dictionary of date identifiers (eg [Date:String]) and only compute identifiers once per date.

For example:

// your configuration parameters could be something like this:

let firstSchoolDay:Date     = // read from configuration
let lastSchoolDay           = // read from configuration
let dayIdentifiers:[String] = // read from configuration 
let skippedDates:Set<Date>  = // read from configuration 

// The global dictionary and function could work like this:

var dayIdentifiers:[Date:Sting] = [:] // global scope (or singleton)
func dayIdentifier(for date:Date) -> String
{
    if let dayID = dayIdentifiers[date]
    { return dayID  }

    let dayID:String = // compute your day ID once according to parameters.
                       // you could use an empty string as a convention for
                       // non school days

                       // a simple way to compute this is to start from
                       // the last computed date (or firstSchoolDay)
                       // and move forward using Calendar.enumerateDates
                       // applying the weekend and offdays rules
                       // and saving day identifiers as you
                       // move forward up to the requested date

    dayIdentifiers[date] = dayID
    return dayID         
}

Answer 2

I figured out how to keep track of the moving dates, while also not accounting for weekends and updating the value every time it is checked.

func getCurrentDay() -> Int {

    let lastSetDay = //Get the last value of the set day
    let lastSetDayDate = //Get the last time the day was set
    var numberOfDays: Int! //Calculate number of recurring days, for instance an A, B, C, D day schedule would be 4

    var currentDay = lastSetDay
    var currentIteratedDate = lastSetDayDate

    while Calendar.current.isDate(currentIteratedDate, inSameDayAs: Date()) == false {
        currentIteratedDate = Calendar.current.date(byAdding: .day, value: 1, to: currentIteratedDate)!
        if !Calendar.current.isDateInWeekend(currentIteratedDate) {
            currentDay += 1
        }
        if currentDay > numberOfDays {
            currentDay = 1
        }
    }

    if Calendar.current.isDate(currentIteratedDate, inSameDayAs: Date()) == false {
        //Save new day
        //Save new date
    }

    return currentDay
}