Cheat sheet on Combine operators for iOS development

allSatisfy(_:)

Publishes true if all elements match the condition. Publishes false & completes if it receives an element that does not match the condition.

append(_:)

Appends the specified elements after the upstream publisher completes.

collect(_:)

Collects up to the specified number of elements and emits them in an array.

combineLatest(_:)

Publishes a tuple of the most recent element from multiple publishers when any of them emits a value.

compactMap(_:)

Transforms each element with the provided closure and publishes any returned non-nil optional result.

contains(_:)

Publishes true & completes after receiving a matching value, or false when upstream publisher completes without producing a matching value.

count()

Publishes the count of all received elements when the upstream publisher completes.

dropFirst(_:)

Omits a specified number of elements, then republishes all remaining elements.

drop(while:)

Omits elements until a given closure returns false, then republishes all remaining elements.

filter(_:)

Republishes all elements that match a provided closure.

first()

Publishes the first element of the upstream publisher, then completes.

first(where:)

Publishes the first element of a stream that satisfies a condition, then completes.

flatMap(maxPublishers:_:)

Transforms all elements from an upstream publisher into a new publisher.

ignoreOutput()

Ignores all elements and passes along only the upstream publisher's completion state.

last()

Publishes the last element of the upstream publisher after it completes.

last(where:)

Publishes the last element that satisfies a condition after the upstream publisher completes.

map(_:)

Transforms each element it receives from the upstream publisher with the provided closure.

max()

Publishes the maximum value received after the upstream publisher completes.

merge(with:)

Publishes an element whenever any of the upstream publishers emits an element.

min()

Publishes the minimum value received after the upstream publisher completes.

output(at:)

Republishes an element specified by its position, or completes if upstream publisher completes before the specified element.

output(in:)

Republishes elements specified by a range of positions.

prefix(_:)

Republishes elements up to a specified maximum count.

prefix(while:)

Emits values while elements meet the specified condition, otherwise it completes.

prepend(_:)

Prepends elements with the specified values.

reduce(_:_:)

Applies a closure to all elements and publishes a final result when the upstream publisher completes.

removeDuplicates()

Publishes an element only if it doesn't match the previous element.

replaceNil(with:)

Replaces nil elements with the provided element.

scan(_:_:)

Transforms elements by applying a closure that receives its previous return value and the next element from the upstream publisher.

switchToLatest()

Republishes elements sent by the most recently received publisher.

zip(_:)

Waits until both publishers emit an element, then publishes the oldest unconsumed element from each one as a tuple.