DateTemplates

DateTemplates is a library that provides a simple way to generate date formatting templates that can be used to format dates in all Apple platforms and Linux. With a declarative Swift syntax that's easy to read and natural to write, DateTemplate works seamlessly with DateFormatter. Automatic support for localization makes it easier than ever to work with custom date formats.

Declarative Syntax

DateTemplates uses a declarative syntax so you can simply state which elements should be included in the formatted date string. For example, you can write that you want a date consisting of full week day, and time, without having to worry about template symbols, localization discrepancies, or clock-format.

let template = DateTemplate().dayOfWeek(.full).time()
print(template.localizedString(from: Date()))

This template will render dates as follows:

Locale	Formatted String
"en_US"	"Thursday 12:00 AM"
"es_ES"	"jueves, 0:00"
"ja_JP"	"木曜日 0:00"
"ru_RU"	"четверг 00:00"
"ar_EG"	"الخميس ١٢:٠٠ ص"

Examples

The following examples assume "America/Los_Angeles" time-zone and "en_US" locale:

Template	Formatted String
DateTemplate().time().timeZone()	"12:00 AM PST"
DateTemplate().dayOfWeek().day().month(.abbreviated).year()	"Thu, Jan 1, 1970"
DateTemplate().day().month(.abbreviated).year(length: 2).era()	"Mar 15, 44 BC"

Under the Hood

A DateTemplate instance provides a declarative way to composing date formatting template strings. These are regular, standard templates that can be used with DateFormatter.

let dateTemplate = DateTemplate().year().month().day().hours().minutes()
print(dateTemplate.template) // "yMdjmm"

These template strings can be used to generate a localized date format:

let template = DateTemplate().year().month().day().hours().minutes().template
let format = DateFormatter.dateFormat(fromTemplate: template, options: 0, locale: nil) ?? template
print(format) // "M/d/y, h:mm a" (assuming en_US locale)

For convenience, DateTemplate provides a localizedFormat method:

let template = DateTemplate().year().month().day().hours().minutes()
let format = template.localizedFormat()
print(format) // "M/d/y, h:mm a" (assuming en_US locale)

Localized format strings can be used with DateFormatter to convert dates to strings (and viceversa):

let formatter = DateFormatter()
formatter.locale = Locale(identifier: "en_US")
formatter.dateFormat = format // "M/d/y, h:mm a" 
formatter.timeZone = TimeZone(secondsFromGMT: 0)
let string = formatter.string(from: Date(timeIntervalSince1970: 0))
print(string) // "1/1/1970, 12:00 AM"

For convenience, DateTemplate provides a localizedString method:

let template = DateTemplate().year().month().day().hours().minutes()
let string = template.localizedString(from: Date(timeIntervalSince1970: 0),
                                      locale: Locale("en_US"), 
                                      timeZone: TimeZone(secondsFromGMT: 0))
print(string) // "1/1/1970, 12:00 AM"

Benefits of Using DateTemplates

These are some benefits:

• Easily composition of custom localized formats: specify which elements to include, and don't worry about the rest.
• Bug prevention:
  • Ever heard of the difference between "YYYY" and "yyyy"?
  • How about the difference between "MM" and "mm"?
  • 12hr vs. 24 hr clock
  • etc.
• Not reinventing the wheel. Based on Unicode Locale Data Markup Language standard for dates.
• 100% compatible with DateFormatter.

Installation

For Xcode projects 🛠

Add Swift Package to Xcode via File -> Swift Packages -> Add Package Dependency...

For Swift Packages 📦

Add DateTemplates dependency to Packages.swift

dependencies: [
    // other dependencies
    .package(url: "https://github.com/eneko/DateTemplates", from: "0.1.0")
],
targets: [
    .target(name: "YourPackage", dependencies: [
        // other dependencies
        "DateTemplates"
    ]),
    // other targets
]

License

MIT License

Copyright (c) 2020 Eneko Alonso