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Update "Creating Results" section in README

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Michael Bull 2019-08-24 00:31:23 +01:00
parent 31808eb99c
commit ed430c4eca
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@ -36,17 +36,6 @@ using the `Result` type in other languages:
### Creating Results ### Creating Results
To begin incorporating the `Result` type into an existing codebase, you can
wrap functions that may fail (i.e. throw an `Exception`) with
[`Result.of`][result-of]. This will execute the block of code and `catch` any
`Exception`, returning a `Result<T, Exception>`.
```kotlin
val result: Result<Customer, Exception> = Result.of {
customerDb.findById(id = 50) // could throw SQLException or similar
}
```
The idiomatic approach to modelling operations that may fail in Railway The idiomatic approach to modelling operations that may fail in Railway
Oriented Programming is to avoid throwing an exception and instead make the Oriented Programming is to avoid throwing an exception and instead make the
return type of your function a `Result`. return type of your function a `Result`.
@ -61,6 +50,17 @@ fun checkPrivileges(user: User, command: Command): Result<Command, CommandError>
} }
``` ```
To incorporate the `Result` type into an existing codebase that throws
exceptions, you can wrap functions that may `throw` with
[`runCatching`][result-runCatching]. This will execute the block of code and
`catch` any `Throwable`, returning a `Result<T, Throwable>`.
```kotlin
val result: Result<Customer, Throwable> = runCatching {
customerDb.findById(id = 50) // could throw SQLException or similar
}
```
Nullable types, such as the `find` method in the example below, can be Nullable types, such as the `find` method in the example below, can be
converted to a `Result` using the `toResultOr` extension function. converted to a `Result` using the `toResultOr` extension function.
@ -201,9 +201,9 @@ This project is available under the terms of the ISC license. See the
[`LICENSE`](LICENSE) file for the copyright information and licensing terms. [`LICENSE`](LICENSE) file for the copyright information and licensing terms.
[result]: https://github.com/michaelbull/kotlin-result/blob/master/src/main/kotlin/com/github/michaelbull/result/Result.kt#L10 [result]: https://github.com/michaelbull/kotlin-result/blob/master/src/main/kotlin/com/github/michaelbull/result/Result.kt#L10
[result-ok]: https://github.com/michaelbull/kotlin-result/blob/master/src/main/kotlin/com/github/michaelbull/result/Result.kt#L30 [result-ok]: https://github.com/michaelbull/kotlin-result/blob/master/src/main/kotlin/com/github/michaelbull/result/Result.kt#L31
[result-err]: https://github.com/michaelbull/kotlin-result/blob/master/src/main/kotlin/com/github/michaelbull/result/Result.kt#L35 [result-err]: https://github.com/michaelbull/kotlin-result/blob/master/src/main/kotlin/com/github/michaelbull/result/Result.kt#L36
[result-of]: https://github.com/michaelbull/kotlin-result/blob/master/src/main/kotlin/com/github/michaelbull/result/Result.kt#L17 [result-runCatching]: https://github.com/michaelbull/kotlin-result/blob/master/src/main/kotlin/com/github/michaelbull/result/Factory.kt#L11
[swalschin-rop]: https://fsharpforfunandprofit.com/rop/ [swalschin-rop]: https://fsharpforfunandprofit.com/rop/
[wiki]: https://github.com/michaelbull/kotlin-result/wiki [wiki]: https://github.com/michaelbull/kotlin-result/wiki
[unit-tests]: https://github.com/michaelbull/kotlin-result/tree/master/src/test/kotlin/com/github/michaelbull/result [unit-tests]: https://github.com/michaelbull/kotlin-result/tree/master/src/test/kotlin/com/github/michaelbull/result