Kotlin-Flow is a declarative, asynchronous programming library that allows developers to handle streams of values over time. It is part of the Kotlin Coroutines library and is designed to handle sequences of values asynchronously. In simple words, A flow is very similar to an Iterator that produces a sequence of values, but it uses suspend functions to produce and consume values asynchronously.
Why we need Kotlin-Flow?
Rx(Reactive Extensions) is used for asynchronous and event-based programming which make easier for data steam and observer pattern like Rx-Java. It also support suspended functions which helps to execute asynchronous tasks in sequences.
How to create Flow?
In Kotlin, Flow builder are the functions which helps us to create new flow. Some of the basic ways to create flows are: -
- flowOf(): Creates a new flow that generate sequence of values based on the provided arguments.
- asFlow(): This create a flow from the given values. It could be sequence, iterator, array, range, or functional type.
- flow{..}: This builder function create flow from suspendable block.
Note:- collect is used to get all the data from stream as they are emitted.
Flow Operators
Kotlin flow operators are functions that can transform, combine, filter, or manipulate the values emitted by a flow. Flow are categorised into two types:
Intermediate operators: These operators create a new Flow and return it without triggering the collection of elements. They are not eagerly executed, meaning they don’t trigger the execution of the flow until a terminal operator is applied. They are used for transforming, filtering, or modifying the original Flow.
Terminal operators: These operators consume the Flow and trigger the execution of the entire flow. Once a terminal operator is applied, the flow starts emitting items, and the entire flow is processed. Some of the terminal operators are: toList, toSet, collect, reduce.
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