Type-safe time calculations in Kotlin, powered by generics.

repo name	kizitonwose/Time
repo link	https://github.com/kizitonwose/Time
homepage
language	Kotlin
size (curr.)	134 kB
stars (curr.)	914
created	2017-10-26
license	MIT License

Time

This library is made for you if you have ever written something like this:

val duration = 10 * 1000

to represent a duration of 10 seconds(in milliseconds) because most methods in Kotlin/Java take duration parameters in milliseconds.

Usage

Showcase

val tenSeconds = 10.seconds
val fiveMinutes = 5.minutes
val twoHours = 2.hours
val threeDays = 3.days
val tenMinutesFromNow = Calendar.getInstance() + 10.minutes
val tenSecondsInMilliseconds = 10.seconds.inMilliseconds

Basics

The main advantage of the library is that all time units are strongly-typed. So, for example:

val tenMinutes = 10.minutes

In the example above, tenMinutes will be of type Interval<Minute>. There are seven time units available, from nanoseconds to days:

val tenNanoseconds = 10.nanoseconds 
// type is Interval<Nanosecond>

val tenMicroseconds = 10.microseconds 
// type is Interval<Microsecond>

val tenMilliseconds = 10.milliseconds 
// type is Interval<Millisecond>

val tenSeconds = 10.seconds 
// type is Interval<Second>

val tenMinutes = 10.minutes 
// type is Interval<Minute>

val tenHours = 10.hours 
// type is Interval<Hour>

val tenDays = 10.days 
// type is Interval<Day>

Operations

You can perform all basic arithmetic operations on time intervals, even of different units:

val duration = 10.minutes + 15.seconds - 3.minutes + 2.hours // Interval<Minute>
val doubled = duration * 2

val seconds = 10.seconds + 3.minutes // Interval<Second>

You can also use these operations with the Calendar class:

val twoHoursLater = Calendar.getInstance() + 2.hours

Conversions

Time intervals are easily convertible:

val twoMinutesInSeconds = 2.minutes.inSeconds // Interval<Second>
val fourDaysInHours = 4.days.inHours // Interval<Hour>

You can also use the converted() method, although you would rarely need to:

val tenMinutesInSeconds: Interval<Second> = 10.minutes.converted()

Comparison

You can compare different time units as well:

50.seconds < 2.hours // true
120.minutes == 2.hours // true
100.milliseconds > 2.seconds // false
48.hours in 2.days // true

Creating your own time units

If, for some reason, you need to create your own time unit, that’s super easy to do:

class Week : TimeUnit {
    // number of seconds in one week
    override val timeIntervalRatio = 604800.0
}

Now you can use it like any other time unit:

val fiveWeeks = Interval<Week>(5)

For the sake of convenience, don’t forget to write those handy extensions:

class Week : TimeUnit {
    override val timeIntervalRatio = 604800.0
}

val Number.weeks: Interval<Week>
    get() = Interval(this)

val Interval<TimeUnit>.inWeeks: Interval<Week>
    get() = converted()

Now you can write:

val fiveWeeks = 5.weeks // Interval<Week>

You can also easily convert to weeks:

val valueInWeeks = 14.days.inWeeks // Interval<Week>

Extras

The library includes some handy extensions for some classes:

val now = Calendar.getInstance() 
val sixHoursLater = now + 6.hours
val fourDaysAgo = now - 4.days

val timer = Timer()
timer.schedule(10.seconds) {
    println("This block will be called in 10 seconds")
}

The library also includes extensions for Android’s Handler class, this is only available if you compile the “time-android” module.

val handler = Handler()
handler.postDelayed({
    Log.i("TAG", "This will be printed to the Logcat in 2 minutes")
}, 2.minutes)

More extensions will be added to the library in the future.

Conversion safety everywhere

For time-related methods in other third-party libraries in your project, if such methods are frequently used, it’s best to write extention functions that let you use the time units in this libary in those methods. This is mostly just one line of code.

If such methods aren’t frequently used, you can still benefit from the conversion safety that comes with this library.

An example method in a third-party library that does something after a delay period in milliseconds:

class Person {
    fun doSomething(delayMillis: Long) {
        // method body
    }
}

To call the method above with a value of 5 minutes, one would usually write:

val person = Person()
person.doSomething(5 * 60 * 1000)

The above line can be written in a safer and clearer way using this library:

val person = Person()
person.doSomething(5.minutes.inMilliseconds.longValue)

If the method is frequently used, you can write an extension function:

fun Person.doSomething(delay: Interval<TimeUnit>) {
    doSomething(delay.inMilliseconds.longValue)
}

Now you can write:

val person = Person()
person.doSomething(5.minutes)

Installation

Add the JitPack repository to your build.gradle:

allprojects {
 repositories {
    maven { url "https://jitpack.io" }
    }
}

Add the dependency to your build.gradle:

• For non-Android projects:

dependencies {
    compile 'com.github.kizitonwose.time:time:<version>'
}

• For Android projects:

dependencies {
    compile 'com.github.kizitonwose.time:time-android:<version>'
}

Contributing

The goal is for the library to be used wherever possible. If there are extension functions or features you think the library should have, feel free to add them and send a pull request or open an issue. Core Kotlin extensions belong in the “time” module while Android extensions belong in “time-android” module.

Inspiration

Time was inspired by a Swift library of the same name - Time.

The API of Time(Kotlin) has been designed to be as close as possible to Time(Swift) for consistency and because the two languages have many similarities. Check out Time(Swift) if you want a library with the same functionality in Swift.

License

Time is distributed under the MIT license. See LICENSE for details.