Everyday ReactiveCocoa

Overview of my thoughts and experience using ReactiveCocoa. Presented at Cocoaheads Brisbane Meetup held on 1 April 2014.

Transcript

1. Everyday ReactiveCocoa Rob Pearson @robpearson
2. Maple Pixel Transit App coming soon ... hopefully
3. Thoughts and Experience using ReactiveCocoa Everyday for 5-6 months
4. FrieNDA.
5. Everyday ReactiveCocoa 1. Review Functional Programming 2. Introduce Functional Reactive Programming 3. Everyday ReactiveCocoa Code Examples
6. Review Functional Programming
7. Functional Programming In functional programming, programs are executed by evaluating expressions ... avoids using mutable state. - Haskell Wiki http://haskell.org/haskellwiki/Functional_programming
8. Functional Building Blocks — Purity — Higher Order Functions
9. Purity f(x) = x + 1
10. Higher Order Functions Input or Output is a Function
11. Functional Reactive Programming
12. Inputs and Outputs "Programs take input and produce output. The output is the result of doing something with the input. Input, transform, output, done." Josh Abernathy - http://blog.maybeapps.com/post/42894317939/input-and-output
13. Inputs — Keyboard (text) input — Click/Touch input — Timers (intervals) — GPS location changes — Resources from web services ...
14. Outputs — UI Changes — Sounds — Persist data somewhere — Push data to the cloud ...
16. Reacting to Signals via subscriptions [[self.transitLocationRepository getTransitLocations] subscribeNext:^(MPXTransitLocation *transitLocation) { // Do something interesting with transit location } error:^(NSError *error) { // Error handling } completed:^{ // Completion handling }];
17. Transit App Example self.canAddNewEverydayTransitTripSignal = [RACSignal combineLatest:@[ self.selectedDepartingStationSignal, self.selectedArrivingStationSignal ] reduce: ^id(MPXTransitLocation *departingTransitLocation, MPXTransitLocation *arrivingTransitLocation) { BOOL isValid = NO; if (departingTransitLocation != nil && arrivingTransitLocation != nil) { isValid = YES; } return @(isValid); }];
19. Boom!
20. Why is FRP better? — Minimal App State — Declarative — Expressive — Different
21. ReactiveCocoa Reactive Functional Programming framework by Github
22. It's all about Signals! (RACSignal) Build the Pipeline
23. Everyday ReactiveCocoa Code Examples
24. Creating Signals - (RACSignal *)runReactiveDatabaseFetchBlock:(FMResultSet *(^)(FMDatabase *database))databaseFetchBlock andMapObjects:(id (^)(FMResultSet * resultSet))mapObjectBlock { // TODO: Rename as this isn't ideal. NSParameterAssert(databaseFetchBlock != nil); NSParameterAssert(mapObjectBlock != nil); RACSignal *databaseFetchSignal = [RACSignal createSignal:^RACDisposable *(id <RACSubscriber> subscriber) { __block FMResultSet *resultSet = nil; [self.databaseQueue inDatabase:^(FMDatabase *database) { resultSet = databaseFetchBlock(database); while ([resultSet next]) { id object = mapObjectBlock(resultSet); if (object != nil) { [subscriber sendNext:object]; } } }]; [subscriber sendCompleted]; return [RACDisposable disposableWithBlock:^{ if (resultSet != nil){ [resultSet close]; } }]; }]; return databaseFetchSignal; }
25. Key Value Observing // Bind Transit Trips to Table View [RACObserve(self.viewModel, everydayTransitTrips) subscribeNext:^(id x) { @strongify(self); // Refresh 'Transit Trips' MCSimpleTableSection if needed ... [self.tableView reloadData]; }];
26. Bind a signal to a property RACSignal *titleSignal = [RACObserve(self.viewModel, title) distinctUntilChanged]; RAC(self, title) = [titleSignal deliverOn:[RACScheduler mainThreadScheduler]];
27. React to Delegates/Selectors [[self rac_signalForSelector:@selector(searchBar:textDidChange:) fromProtocol:@protocol(UISearchBarDelegate)] subscribeNext:^(RACTuple *value) { @strongify(self); UISearchBar *searchBar = value.first; if (searchBar == self.departingLocationsSearchBar) { [self.viewModel filterDepartingLocationsByName:self.departingLocationsSearchBar.text]; } else { [self.viewModel filterArrivingLocationsByName:self.arrivingLocationsSearchBar.text]; } }];
28. React to Button Commands // Add Button self.addButton.rac_command = [[RACCommand alloc] initWithEnabled:self.viewModel.canAddNewEverydayTransitTripSignal signalBlock:^RACSignal *(id input) { // Add New Transit Trip }]; [self.addButton.rac_command.errors subscribeNext:^(id x) { // TODO: Add support for error handling from the command. }];
29. React to Control Events MCSimpleTableCell *everydayTransitTripCell = [[MCSimpleTableCell alloc] init]; everydayTransitTripCell.cellIdentifier = @"cellwithswitch"; everydayTransitTripCell.configureBlock = ^(MCSimpleTableCell *cell, UITableViewCell *tableCell) { tableCell.textLabel.text = trip.tripDescription; UISwitch *control = [[UISwitch alloc] initWithFrame:CGRectZero]; control.on = trip.isEnabled; tableCell.accessoryView = control; tableCell.selectionStyle = UITableViewCellSelectionStyleNone; [[control rac_signalForControlEvents:UIControlEventValueChanged] subscribeNext:^(id x) { @strongify(self); [self.viewModel toggleTripEnablementWithEverydayTransitTripId:trip.everydayTransitTripId]; }]; }; [everydayTransitTripsSection addCell:everydayTransitTripCell];
30. Real Power is combing and chaining signals
31. Transit App Dashboard Inputs: * Transit Trip Times * Location Updates * Time Updates Output: * Next Transit Service based on time/location
32. Protips — Start by reading IntroToRx.com — Start small and iterate. — Asks questions by opening issues at http:// github.com/ReactiveCocoa/
33. Challenges — ReactiveCocoa Doco — Thinking like a Functional Programmer — Debugging — Unit Testing
34. References — Github Repo: http://github.com/ReactiveCocoa/ — Ray Wenderlich Tutorial: https://bit.ly/1rXA31Y — Big Nerd Ranch Tutorial: https://bit.ly/1mp04mI — FRP on iOS by Ash Furrow: https://leanpub.com/ iosfrp — Brent Simmons on ReactiveCocoa: https://bit.ly/ PcyjCL
35. Questions?