This is Understanding Combine, written by Matt Neuburg. Corrections and suggestions are greatly appreciated (you can comment here). So are donations; please consider keeping me going by funding this work at http://www.paypal.me/mattneub. Or buy my books: the current (and final) editions are iOS 15 Programming Fundamentals with Swift and Programming iOS 14. Thank you!
by Matt Neuburg
Unifying Asynchronicitywhat Combine is all about
Publish and Subscribethe heart of the Combine architecture
Introducing Operatorstransformations between publisher and subscriber
Pipelinesat last, some practical Combine examples!
Stopping a Pipelinecancel and AnyCancellable; finished completions
Failuresfailure completions; transmutation of failures; Never
Typesgeneric Output and Failure types
AnyCancellableretaining the subscriber with store
One-Shot Subscribersretaining the subscriber without store
Custom Subscribersthe Subscriber protocol
Notification Center Publisherreceiving notifications
Data Task PublisherURLSession downloads
Future and Deferredturn any asynchronous code into a publisher
Timer Publisherrepeated intervals; also, connect and autoconnect
Key–Value Observing Publisheruse it wherever you were already using KVO
Publisheda better KVO
SubjectPassthroughSubject and CurrentValueSubject; Subject as subscriber
Value PublishersJust, Optional, Result, Sequence, Empty, Fail
Recordencapsulate the whole output of a pipeline
Custom Publishersthe Publisher protocol; the Subscription protocol
Transformers and Blockerschange the value or stop it
Maptransform a value
Scantransform a value based on the previous value
Filterto block or not to block
RemoveDuplicatesblock based on the previous value
CompactMapnil means block
FlatMapproducing a publisher within the pipeline; AnyPublisher; serializing asynchronicity; failing without terminating; exerting backpressure
SwitchToLatesta cousin of flatMap
No Valuesblock all values (ignoreOutput), and its opposite (replaceEmpty)
Accumulatorscapture values and wait
Partitionerssubranges
Joinersmany publishers, one subscriber
Splittersone publisher, many subscribers; more about Subjects
Timersplaying with time
Delaywait a while
Debouncewait for a pause
Timeoutnot too slow
Throttlenot too fast
MeasureIntervalhow long was that?
Buffersmoothe out timing differences
Error Handlerstransforming failures
MapErrorturn one error into another
ReplaceErrorturn failure into success
SetFailureTypeturn Never into failure
Catchturn failure into anything you like
Retryturn failure into try again
Codablesencode and decode
Threadersreceive(on:) and subscribe(on:)
WrapperseraseToAnyPublisher and makeConnectable
Debuggersfigure out how your pipeline works
Composed Operatorsmaking an operator, the easy way
Custom Operatorsmaking an operator, the hard way