Some Code Patterns

VIDEO: https://vimeo.com/124773343

This talk covers a handful of code patterns that were successful on my recent projects. Some of these patterns include Block Safety, "Tell, Don't Ask", Using DataSources for your network-based *Service objects.

Transcript

1. SOME CODE PATTERNS
2. STORYBOARDS
3. UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Settings" bundle:nil];
4. // .h extern NSString * const StoryboardNameSettings; // .m NSString * const StoryboardNameSettings = @"Settings"; // use new constant UIStoryboard *storyboard = [UIStoryboard storyboardWithName:StoryboardNameSettings bundle:nil];
5. @implementation UIStoryboard (Additions) + (UIStoryboard *)pch_settingsStoryboard { return [UIStoryboard storyboardWithName:@"Settings" bundle:nil]; } @end
6. @implementation UIStoryboard (Additions) + (UIStoryboard *)pch_settingsStoryboard { if ( UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad ) return [UIStoryboard storyboardWithName:@"Settings~iPad" bundle:nil]; } else { return [UIStoryboard storyboardWithName:@"Settings~iPhone" bundle:nil]; } } @end
7. CUSTOM ERRORS
8. #define ERROR_DOMAIN @"com.mikezornek.json-parser" @implementation NSError (MZJSONParserErrors) + (NSError *)mdz_invalidJsonError { return [NSError errorWithDomain:ERROR_DOMAIN code:1001 userInfo:@{NSLocalizedDescriptionKey : @"JSON was malformed and could not be parsed."}]; } @end
9. BLOCK SAFETY
10. - (void)tellClientToDoItWithCompletion:(CompletionType)completion { [self.client doIt:^(NSError *error) { completion(); }]; }
11. - (void)tellClientToDoItWithCompletion:(CompletionType)completion { [self.client doIt:^(NSError *error) { if (completion) { completion(); } }]; }
12. // In even a simple network call this can get out of hand... - (void)downloadTracksFromURL:(NSURL *)url completionHandler:(void (^)(NSArray *tracks, NSError *error))completion { NSURLSessionDataTask *dataTask = [self.session dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { if (!error) { NSError *trackError; NSArray *tracks = [self tracksFromData:data error:&trackError]; if (tracks) { if (completionHandler) { completionHandler(tracks, nil); } } else { if (completionHandler) { completionHandler(nil, trackError); } } } else { if (completionHandler) { completionHandler(nil, error); } } }]; [dataTask resume]; }
13. // Look how nicer it gets when you can assume the block is present... - (void)downloadTracksFromURL:(NSURL *)url completionHandler: (void (^)(NSArray *tracks, NSError *error))completion { // Some code or method to verify the completion block is not null NSURLSessionDataTask *dataTask = [self.session dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { if (!error) { NSError *trackError; NSArray *tracks = [self tracksFromData:data error:&trackError]; tracks ? completionHandler(tracks, nil) : completionHandler(nil, trackError); } else { completionHandler(nil, error); } }]; [dataTask resume]; }
14. MAKE A MACRO
15. MACROS #define BLOCK_CALL(block, ...) ({ if (block) block(__VA_ARGS__); else nil; })
16. PROVIDE A DEFAULT BLOCK BEHAVIOR
17. DEFAULT BLOCK - (void)processPhoneList:(NSArray *)list completion: (PhoneListCompletionHandler)incomingCompletion { PhoneListCompletionHandler completion = (incomingCompletionHandler != NULL) ? incomingCompletionHandler : ^{ NSLog(@"processPhoneList: did complete"); }; // When the time comes, look ma' no need to check for nil! completion() }
18. MAKE THE BLOCK REQUIRED
19. USING ASSERTS NSParameterAssert(block != nil);
20. NEW IN XCODE 6.31 // as long as the type is a simple object or block pointer. - (nullable AAPLListItem *)itemWithName:(nonnull NSString *)name; - (NSInteger)indexOfItem:(nonnull AAPLListItem *)item; 1 https://developer.apple.com/swift/blog/?id=25
21. NEW IN XCODE 6.31 @property (copy, nullable) NSString *name; @property (copy, readonly, nonnull) NSArray *allItems; 1 https://developer.apple.com/swift/blog/?id=25
22. TELL, DON'T ASK (DEPENDENCY INJECTION)
23. The core idea of the Tell, Don't Ask pattern is that any *ViewController or *Service or *Store you build should, when initialized or otherwise "prepared", have all the information it needs to do its job. It should not ask the global state for information. -- Mike Zornek, right now
26. SOME MORE EXAMPLES: ▸ +[NSDate date] ▸ NSNotificationCenter ▸ NSUserDefaults ▸ SessionManager ▸ *Store / *Service
27. But I don't want to manually pass around all these state objects! — Someone complained
28. SOLUTIONS ▸ prepareForSegue:sender: ▸ pushViewController:animated: ▸ ... or a dedicated framework
29. Frameworks ▸ http://typhoonframework.org/ ▸ http://objection-framework.org/ Articles ▸ http://www.objc.io/issue-15/dependency-injection.html ▸ https://www.bignerdranch.com/blog/dependency-injection-ios/
30. LAUNCH MENU
32. struct LaunchMenuItem { let title: String let details: String let runAction: () -> () } struct LaunchMenuSection { let title: String let items: [LaunchMenuItem] } struct LaunchMenu { let sections: [LaunchMenuSection] }
33. WEATHERDEMO https://github.com/zorn/WeatherDemo
34. DATASOURCES FOR *Service OBJECTS
40. WEATHERDEMO https://github.com/zorn/WeatherDemo
41. The End?