In this series of articles , we are discussing about Kotlin flows and in this article we will discuss about Flows Terminal operators

Code gist can be found in https://gist.github.com/vprabhu/20bf26e73451ae9ea0876e3780537d4a

Whats is Terminal Operators?

• Its a suspend function

• Starts the flow's collection

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Terminal Operators List

There are some terminal operators which we can used to start the collection of the flow

Collect()

• collects the given flow

• commonly used with onEach() , onCompletion() and catch to collect all emitted values

    val flow = flow {
        delay(200)
        emit(1)
  
        delay(200)
        emit(2)
  
        delay(200)
        emit(2)
    }
  
      flow.collect { receivedValue ->
                println("Collect Received value 1: $receivedValue")
                /** Output :
                 * Collect Received value 1: 1
                 * Collect Received value 1: 2
                 * Collect Received value 1: 2
                 */
      }
  

first() and last()

• first() returns the first element emitted by flow and cancels the flow's cancellation.

• last() returns the last element emitted by the flow.

val itemFirst = flow.first()
println("first() flow : $itemFirst")
/** Output :
 * first() flow : 1
 */

val itemLast = flow.last()
println("last() flow : $itemLast")
/**
 * last() flow : 2
 */

single()

• Collects the only and one value from flow

• If flow emits multiple values , it throws the following error

Exception in thread "main" java.lang.IllegalArgumentException: Flow has more than one element

val singleFlow = flow {
        emit("Single Emitted value")
    }

val itemSingle = singleFlow.single()
println("single() flow : $itemSingle") 
/**
*  output : single() flow : Single Emitted value
*/

toSet()

• converts the flow output to set

val setFLow = flow.toSet()
println("toSet() flow : $setFLow")
/**
 * Output :  toSet() flow : [1, 2]
 */

toList()

• converts the flow to list

val listFLow = flow.toList()
println("toList() flow : $listFLow")
/**
 * toList() flow : [1, 2, 2]
 */

In the next article , we will discuss about Exception Handling in Flow.

Please leave your comments to improve.

Happy and Enjoy coding