WithPrevious<T> class

A StreamTransformer that pairs each value in a stream with its previous value.

This transformer takes each value from the source stream and emits a record containing both the current value and the previous value. The first emission will have the initialPrevious value, if provided, as the previous value.

The transformed stream emits a PreviousValuePair, which is a record type containing:

• previous: The previous value in the stream (or initialPrevious for the first emission)
• current: The current value from the stream

Example:

final stream = Stream.fromIterable([1, 2, 3]);
final withPrevious = stream.transform(WithPrevious(0));
// Emits: (previous: 0, current: 1)
//        (previous: 1, current: 2)
//        (previous: 2, current: 3)

Inheritance

• Object
• StreamTransformerBase<T, PreviousValuePair<T>>
• WithPrevious

Constructors

WithPrevious.new([T? initialPrevious])

Creates a WithPrevious transformer.

Properties

hashCode → int

The hash code for this object.

no setter, inherited

initialPrevious → T?

The initial previous value to use for the first emission.

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

bind(Stream<T> stream) → Stream<PreviousValuePair<T>>

Transforms the provided stream.

override

cast<RS, RT>() → StreamTransformer<RS, RT>

Provides a StreamTransformer<RS, RT> view of this stream transformer.

inherited

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited