krontab/README.md

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# krontab
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[ ![Download](https://api.bintray.com/packages/insanusmokrassar/InsanusMokrassar/krontab-mpp/images/download.svg) ](https://bintray.com/insanusmokrassar/InsanusMokrassar/krontab-mpp/_latestVersion)
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[![Maven Central](https://maven-badges.herokuapp.com/maven-central/dev.inmo/krontab/badge.svg)](https://maven-badges.herokuapp.com/maven-central/dev.inmo/krontab)
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[![Build Status](https://travis-ci.com/InsanusMokrassar/krontab.svg?branch=master)](https://travis-ci.com/InsanusMokrassar/krontab)
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Library was created to give oppotunity to launch some things from time to time according to some schedule in
runtime of applications.
| Table of content |
|---|
| [ How to use ](#how-to-use) |
| [ How to use: Including in project ](#including-in-project) |
| [ How to use: Config from string ](#config-from-string) |
| [ How to use: Config via builder (DSL preview) ](#config-via-builder) |
| [ How to use: KronScheduler as a Flow ](#KronScheduler-as-a-Flow) |
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## How to use
There are several ways to configure and use this library:
* From some string
* From builder
Anyway, to start some action from time to time you will need to use one of extensions/functions:
```kotlin
val kronScheduler = /* creating of KronScheduler instance */;
kronScheuler.doWhile {
// some action
true // true - repeat on next time
}
```
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### Including in project
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If you want to include `krontab` in your project, just add next line to your
dependencies part:
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```groovy
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implementation "dev.inmo:krontab:$krontab_version"
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```
Next version is the latest currently for the library:
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[ ![Download](https://api.bintray.com/packages/insanusmokrassar/InsanusMokrassar/krontab-mpp/images/download.svg) ](https://bintray.com/insanusmokrassar/InsanusMokrassar/krontab-mpp/_latestVersion)
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For old version of Gradle, instead of `implementation` word developers must use `compile`.
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### Config from string
Developers can use more simple way to configure repeat times is string. String configuring
like a `crontab`, but with a little bit different meanings:
```
/-------- Seconds
| /------ Minutes
| | /---- Hours
| | | /-- Days of months
| | | | / Months
| | | | |
* * * * *
```
It is different with original `crontab` syntax for the reason, that expected that in practice developers
will use seconds and minutes with more probability than months (for example). In fact, developers will use something
like:
```kotlin
doWhile("/5 * * * *") {
println("Called")
true // true - repeat on next time
}
```
Or more version:
```kotlin
doInfinity("/5 * * * *") {
println("Called")
}
```
Both of examples will print `Called` message every five seconds.
### Config via builder
Also this library currently supports DSL for creating the same goals:
```kotlin
val kronScheduler = buildSchedule {
seconds {
from (0) every 5
}
}
kronScheduler.doWhile {
println("Called")
true // true - repeat on next time
}
```
Or
```kotlin
val kronScheduler = buildSchedule {
seconds {
0 every 5
}
}
kronScheduler.doWhile {
println("Called")
true // true - repeat on next time
}
```
Or
```kotlin
val kronScheduler = buildSchedule {
seconds {
0 every 5
}
}
kronScheduler.doInfinity {
println("Called")
}
```
All of these examples will do the same things: print `Called` message every five seconds.
### KronScheduler as a Flow
Any `KronScheduler`can e converted to a `Flow<DateTime` using extension `asFlow`:
```kotlin
val kronScheduler = buildSchedule {
seconds {
0 every 1
}
}
val flow = kronScheduler.asFlow()
```
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So, in this case any operations related to flow are available and it is expected that they will work correctly. For
example, it is possible to use this flow with `takeWhile`:
```kotlin
flow.takeWhile {
condition()
}.collect {
action()
}
```