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Lighter View Controllers
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Chris Eidhof | @chriseidhof
February 18, 2014
Programming
5
450
Lighter View Controllers
Talk at Cocoaheads.nl
(Architecture image by Manu Cornet)
Chris Eidhof | @chriseidhof
February 18, 2014
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Transcript
Lighter View Controllers Chris Eidhof CocoaHeads NL
MVC Model View Controller
MVC Model View Controller Massive View Controller
None
What's the largest file? find . -name "*.m" -exec wc
-l "{}" \; | sort -n
Steps Project: A complete OS in < 20K lines
View Controllers are the least reusable part
A view controller intermediates between model and view
Model logic
View logic
View layout
Web Service
Too much already?
Delegates
IBActions ?
Pragma marks ??
None
Child View Controllers
Table View Controllers ☆ Editing Mode ☆ Keyboard notifications ☆
Flashing scroll indicators ☆ Clearing Selection ☆ Pull to Refresh
None
None
View Controller Transitions
None
Pulling out protocols
For example: UITableViewDataSource
Creating a separate data source object @interface FetchedResultsControllerDataSource : NSObject
<UITableViewDataSource, NSFetchedResultsControllerDelegate>
Creating a separate data source object - (NSInteger)numberOfSectionsInTableView:(UITableView*)t { return
self.fetchedResultsController.sections.count; }
Creating a separate data source object - (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)sectionIndex {
id<NSFetchedResultsSectionInfo> section; section = self.frc.sections[sectionIndex]; return section.numberOfObjects; }
Creating a separate data source object Working with the delegate
- (UITableViewCell*)tableView:(UITableView*)tv cellForRowAtIndexPath:(NSIndexPath*)ip { id object = [self objectAtIndexPath:indexPath]; id cell = [tv dequeueReusableCellWithIdentifier:ruI forIndexPath:ip]; [self.delegate configureCell:cell withObject:object]; return cell; }
Advantages of a separate data source ☆ Lighter view controller
☆ Testable ☆ Reusable And you can do this for other protocols, too...
A separate data source ☆ NSArrayDataSource ☆ NSFRCollectionViewController ☆ ...
Categories
Configuring a cell - (UITableViewCell*)tableView:(UITableView*)tv cellForRowAtIndexPath:(NSIndexPath*)ip { PhotoCell *cell =
[tableView dequeueReusableCellWithIdentifier:@"PhotoCell"]; Photo *photo = [self itemAtIndexPath:indexPath]; cell.photoTitleLabel.text = photo.name; NSString* date = [self.dateFormatter stringFromDate:photo.creationDate]; cell.photoDateLabel.text = date; }
Configuring a cell Pulling out the reusable part @implementation PhotoCell
(ConfigureForPhoto) - (void)configureForPhoto:(Photo *)photo { self.photoTitleLabel.text = photo.name; NSString* date = [self.dateFormatter stringFromDate:photo.creationDate]; self.photoDateLabel.text = date; } @end
Configuring a cell The refactored delegate method - (UITableViewCell *)tableView:(UITableView
*)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { PhotoCell *cell = [tableView dequeueReusableCellWithIdentifier:PhotoCellIdentifier]; [cell configureForPhoto:[self itemAtIndexPath:indexPath]]; return cell; }
Using Interface Builder
None
Intentions
Intentions View Controllers may only contain code that effects view
changes in response to data changes. Source: http://bendyworks.com/geekville/articles/ 2014/2/single-responsibility-principle-ios
Intentions The IBAction macro must not be used in a
View Controller
Intentions The @interface block in a View Controller's header file
must be blank.
Intentions A View Controller may not implement any extra *Delegate
or *DataSource protocols except for observing Model changes.
Intentions A View Controller may only do work in viewDidLoad
(or awakeFromNib), viewDidAppear, viewDidDisappear, and in response to an observed change in the model layer.
None
Testing
Testing View controllers are notoriously hard to test → Make
them light.
Commercial Break
None
None
Questions? @chriseidhof