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DateTransformer

A small framwork for transforming Dates to Strings, and Strings to Dates

DateTransformer is a small library for transforming strings to dates, and dates to strings. The library uses a relativley unknown class in Foundation called NSValueTransformer. This class is meant to be used to transform one value to another, and be subclassed to support transforming your types.

Installation

Requirements

  • Swift 4

Carthage

Copy and paste the following into your Cartfile

github "Chandlerdea/DateTransformer"

Manual

You can just drop DateTransformer.xcodeproj into your project and then add DateTransformer.framework to your app’s embedded frameworks.

Use

There are 2 NSValueTransformer subclasses you can use, StringToDateTransformer, TimeIntervalToStringTransformer.

StringToDateTransformer

This class's forward transformation type is Date, and it allows reverse transformatio. That means that you can either take a String and transform it into a Date, or vice versa. This can be useful for taking string representaions of dates from an api and transform them into Date objects. By default, the class uses the format yyyy-MM-dd'T'HH:mm:ssZ to create dates. So if your api sends date strings in a different format, you'll have to pass the custom format to the date transformer. There is also a TimeZone argument, for applying a TimeZone to the returned Date. The default is Date(secondsFromGMT: 0), and your date strings should always be in UTC. Here's an example using a custom format:

let someApiData: [String: String] = ....
let createdAtString: String = someApiData["created_at"]!
let transformer: StringToDateTransformer = StringToDateTransformer()
let dateFormat: String = "EEEE, MMM d, yyyy"
if let createdAt: Date = transformer.transformString(createdAtString, dateFormat: dateFormat) {
  // do something with the date
}

You can also do reverse transformations, from Date to String. By default, the class uses the format EEEE, MMM d, yyyy to create the date strings. It is also important to note that the passed in date will have the system time zone applied by default. There is a TimeZone argument that allows you to pass a custom time zone that will be applied to the date. Here's an example:

let date: Date = Date(timeIntervalSince1970: 0)
let format: String = "MM/dd/yyyy"
let transformer: StringToDateTransformer = StringToDateTransformer()
if let result: String = transformer.transformDate(date, dateFormat: format) {
  // "01/01/1970"
}

TimeIntervalToStringTransformer

TimeIntervalToStringTransformer transforms a TimeInerval to a String. A usecase would be if you were counting down from a date in the future, and you wanted to display the number of hours, minutes, and seconds to the user. The default format used by the class is EEEE, MMM d, yyyy. As before, it is important to note that the passed in timeInterval will have the system time zone applied by default. There is a timeZone argument that allows you to pass a custom time zone that will be applied to the date Here's an example:

let secondsToFutureDate: TimeInterval = ...
let dateFormat: String = "HH:mm:ss"
let transformer: TimeIntervalToStringTransformer = TimeIntervalToStringTransformer(dateFormat: dateFormat)
if let countdownString: String = transformer.transformTimeInterval(secondsToFutureDate) {
  // "01:01:01"
}

Support

If you find any bugs, or have any critiques, please open a PR and I will fix them as soon as I can. And if you feel the need to add some more tests, you're more than welcome!