https://github.com/datafabricrus/resource-iterator

A simple Kotlin library providing ResourceIterator which is an AutoCloseable kotlin Iterator
https://github.com/datafabricrus/resource-iterator

closeable iterator js jvm jvm-library kotlin kotlin-library kotlin-sequence multiplatform-kotlin-library sequence

Last synced: about 1 month ago
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A simple Kotlin library providing ResourceIterator which is an AutoCloseable kotlin Iterator

• Host: GitHub
• URL: https://github.com/datafabricrus/resource-iterator
• Owner: DataFabricRus
• License: apache-2.0
• Created: 2023-11-27T16:16:25.000Z (about 1 year ago)
• Default Branch: master
• Last Pushed: 2024-07-26T10:30:24.000Z (5 months ago)
• Last Synced: 2024-10-15T03:21:44.266Z (3 months ago)
• Topics: closeable, iterator, js, jvm, jvm-library, kotlin, kotlin-library, kotlin-sequence, multiplatform-kotlin-library, sequence
• Language: Kotlin
• Homepage:
• Size: 97.7 KB
• Stars: 1
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
## Resource Iterator

[![](https://jitpack.io/v/DataFabricRus/resource-iterator.svg)](https://jitpack.io/#DataFabricRus/resource-iterator)

A simple kotlin library providing `ResourceIterator`,

which is an extended `kotlin.collections.Iterator` implementing `AutoCloseable` interface:

```kotlin

interface ResourceIterator : Iterator, AutoCloseable {

    ...

}

```

The standard kotlin-stdlib does not contain `Sequence` or `Iterator` which implement `AutoCloseable` interface

(e.g., see open discussion: [KT-34719](https://youtrack.jetbrains.com/issue/KT-34719/Closeable-Sequences)).

This library complements the standard kotlin functionality with an extended iterator

as well as various utility methods such as `flatMap`, `filter`, etc., similar to `Sequence` methods.

Each of these methods produces a subsequent `ResourceIterator`, closing which also closes the source iterator.

The `ResourceIterator` extends `Iterator`, not `Sequence`, since it is hard to control every standard method-extension

of `Sequence`.

#### Known alternatives:

- JDK `java.util.stream.Stream`

- Apache Jena `org.apache.jena.util.iterator.ExtendedIterator`

- Apache Kafka `org.apache.kafka.common.utils.CloseableIterator`

#### When to use:

If you have some resources which need to be closed after or during iteration,

and you don't want to use JDK or some external heavy library.

For example, `ResourceIterator` is used by [textfile-utils](https://github.com/DataFabricRus/textfile-utils)

(see `cc.datafabric.textfileutils.files.LineReade.kt`).

#### Examples of use:

```kotlin

// with standard collections:

listOf(1, 2).asResourceIterator { println("close outer") }

    .flatMap { x ->

        resourceIteratorOf(21 * x, 42 * x) { println("close inner for $x") }

    }

    .filter { it > 0 }

    .use {

        println("it = ${it.firstOrNull()}")

    }

```

```kotlin

// with jdbc:

fun  Connection.executeQuery(

    query: String,

    extractor: (ResultSet) -> X,

    exec: PreparedStatement.() -> ResultSet

): ResourceIterator {

    val statement = prepareStatement(query)

    val rs = statement.exec()

    return generateResourceIterator({ if (rs.next()) extractor(rs) else null }) { statement.close() }

}

```

#### Available via [jitpack](https://jitpack.io/#DataFabricRus/resource-iterator):

```kotlin

repositories {

    ...

    maven(url = "https://jitpack.io")

}

dependencies {

    implementation("com.github.DataFabricRus.resource-iterator:resource-iterator-jvm:{{latest_version}}")

}

```

#### Apache License Version 2.0