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98 lines
2.4 KiB
Markdown
98 lines
2.4 KiB
Markdown
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# Exceptions handling
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Unfortunatelly, exceptions handling in this library is a bit difficult in some places, but that have at least two reasons: flexibility and usability.
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## "In place" handling
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In case you know, where exceptions are happening, you may use several tools for exceptions catching:
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* Catching with result
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* Catching with callback
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### Catching with result
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If you prefer to receive `Result` objects instead of some weird callbacks, you may use the next syntax:
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```kotlin
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safelyWithResult {
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// do something
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}.onSuccess { // will be called if everything is right
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// handle success
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}.onFailure { // will be called if something went wrong
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// handle error
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it.printStackTrace()
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}.getOrThrow() // will return value or throw exception
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```
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### Catching with callback
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Also there is more simple (in some cases) way to handle exceptions with callbacks:
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```kotlin
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safely(
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{
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// handle error
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it.printStackTrace()
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null // return value
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}
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) {
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// do something
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}
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```
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### Bonus: different types of handling
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There are two types of handling:
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* Just safely - when you are using something to obviously retrieve value or throw exception. When handling callback has been skipped, it will throw exception by default. For example:
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```kotlin
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safely(
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{
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it.printStackTrace()
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"error"
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}
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) {
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error("Hi :)") // emulate exception throwing
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"ok"
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} // result will be with type String
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```
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* Safely without exceptions - almost the same as `safely`, but this type by default allow to return nullable value (when exception was thrown) instead of just throwing (as with `safely`):
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```kotlin
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safelyWithouExceptions {
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// do something
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} // will returns nullable result type
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```
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## Global exceptions handling
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The most simple way to configure exceptions handling is to change `CoroutineContext` when you are creating your `CoroutineScope` for bot processing:
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```kotlin
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val bot = telegramBot("TOKEN")
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bot.buildBehaviour (
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scope = scope,
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defaultExceptionsHandler = {
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it.printStackTrace()
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}
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) {
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// ...
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}
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```
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OR
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```kotlin
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val bot = telegramBotWithBehaviour (
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"TOKEN",
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scope = scope,
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defaultExceptionsHandler = {
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it.printStackTrace()
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}
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) {
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// ...
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}
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```
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Here we have used `ContextSafelyExceptionHandler` class. It will pass default handling of exceptions and will call the block in most cases when something inside of your bot logic has thrown exception.
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