distinctUntilChangedBy() works a lot like distinctUntilChanged(), throwing out equivalent items and only emitting the first of those equivalents. The difference is that distinctUntilChangedBy() takes a "key selector" lambda expression or other function type. This lambda expression is responsible for returning the object that should be used (via == comparisons) to determine what items are equivalent or not.

In this case, our flow is of a series of pairs, and the key selector lambda returns the first() piece of the Pair — in this case, that is the Int value. distinctUntilChangedBy() then ignores Pair objects with duplicate Int values, so only the first of our three 1-based Pair objects is emitted.

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A Simple Flow A Simple SharedFlow A Simple StateFlow catch() combine() Operator debounce() Operator distinctUntilChanged() Operator distinctUntilChangedBy() Operator drop() Operator dropWhile() Operator filter() Operator filterIsInstance() Operator filterNot() Operator filterNotNull() Operator first() and Flow flattenConcat() Operator flattenMerge() Operator Flow Actions Flow onStart() flowOf() flowOn() Flows and Exceptions fold() Operator map() Operator mapLatest() Operator mapNotNull() Operator MutableSharedFlow Replay Option retry() retryWhen() sample() Operator scan() Operator single() and singleOrNull() StateFlow and Content Equality suspend Functions and Flows take() Operator takeWhile() Operator toList() and toSet() withIndex() Operator zip() Operator
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