Data Source Combinators

Eliminating the boilerplate from UITableView and UICollectionView.

Transcript

1. Data$Source$Combinators ©"Robert"Brown"March"2015"@robby_brown
2. Table&Views you're'doing'them'wrong ©"Robert"Brown"March"2015"@robby_brown
3. Overview 1. The&Hard&Way 2. Code&Architecture&Theory 3. The&Be7er&Way ©"Robert"Brown"March"2015"@robby_brown
4. Demo ©"Robert"Brown"March"2015"@robby_brown
5. The$Hard$Way ©"Robert"Brown"March"2015"@robby_brown
6. Cell$Crea'on class CandyTableViewController : UITableViewController { override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return self.candies.count } override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell let candy = self.candies[indexPath.row] cell.textLabel!.text = candy.name cell.accessoryType = UITableViewCellAccessoryType.DisclosureIndicator return cell } } From:&raywenderlich.com ©"Robert"Brown"March"2015"@robby_brown
7. Cell$Crea'on What's'wrong'with'this? • Duplicate+boilerplate • View+controllers+handle+interac5on,+not+data+ sources • Cells+are+o8en+shared+between+table+views • Cells+should+handle+their+own+layout ©"Robert"Brown"March"2015"@robby_brown
8. Cell$Crea'on Why$do$we$see$this$so$o,en? • It's&"standard"&prac.ce • That's&how&I've&always&done&it • My&favorite&tutorial&does&it • Apple&does&it ©"Robert"Brown"March"2015"@robby_brown
9. Cell$Crea'on Why$do$we$see$this$so$o,en? • It's&really&convenient&for&tutorials&to&be&simple ©"Robert"Brown"March"2015"@robby_brown
10. Code%Architecture%Theory ©"Robert"Brown"March"2015"@robby_brown
11. Data$Sources Problems: • Massive(View(Controller • Duplicate(boilerplate ©"Robert"Brown"March"2015"@robby_brown
12. Data$Sources Solu%on: • Single(responsibility0principle • Combinators • Chain(of(responsibility ©"Robert"Brown"March"2015"@robby_brown
13. A"class"should"have"only"one" reason"to"change. —"Single)responsibility"principle ©"Robert"Brown"March"2015"@robby_brown
14. A"class"should"have"only"one" reason"to"change. —"Single)responsibility"principle ©"Robert"Brown"March"2015"@robby_brown
15. Every&class&should&have& responsibility&over&a&single& part&of&the&func6onality...,& and&that&responsibility&should& be&en6rely&encapsulated&by& the&class.1 —"Single)responsibility"principle 1"Wikipedia ©"Robert"Brown"March"2015"@robby_brown
16. Combinators • Technique*from*func/onal*programming • Usually*seen*with*parsers • Generally*represent*a*single,*simple*feature • Focus*on*composi/on • Like*higher>order*func/ons*applied*to*features ©"Robert"Brown"March"2015"@robby_brown
17. Chain&of&Responsibility • Like&a&chain&of&delegates • A&3>&B&3>&C&3>&D&... • If&A&can't&handle&something,&then&try&B&... • Used&to&create&a&sequence&of&combinators ©"Robert"Brown"March"2015"@robby_brown
18. The$Be&er$Way ©"Robert"Brown"March"2015"@robby_brown
19. Cell$Crea'on View%Controller override func viewDidLoad() { super.viewDidLoad() let objects = [] // Get objects here tableView.dataSource = BaseDataSource(objects) { (view, indexPath, object) -> Any in return MyCell.cell(view as! UITableView, name: object as! String) } } ©"Robert"Brown"March"2015"@robby_brown
20. Cell$Crea'on View%Controller override func viewDidLoad() { super.viewDidLoad() let objects = [] // Get objects here let base = BaseDataSource(objects) { (view, indexPath, object) -> Any in return MyCell.cell(view as! UITableView, name: object as! String) } self.dataSource = ReorderableDataSource(base) } ©"Robert"Brown"March"2015"@robby_brown
21. Cell$Crea'on Cell class MyCell: SmartTableViewCell { @IBOutlet weak var titleLabel: UILabel! class func cell(tableView: UITableView, name: String) -> Self { let cell = self.cell(tableView) cell.titleLabel.text = name return cell } } ©"Robert"Brown"March"2015"@robby_brown
22. Cell$Crea'on Why$is$this$be*er? • Fewer&lines&of&code • Boilerplate&removed • Behavior&can&be&changed&with&the&data&source(s) • The&data&source&can&work&with&table&and&collec=on& views • Easier&to&build&combinators ©"Robert"Brown"March"2015"@robby_brown
23. Dynamic(Behaviors • Array • Mul)*dimensional2array • Filtering • Reordering • Edi)ng • Index2)tles ©"Robert"Brown"March"2015"@robby_brown
24. Considera*ons • The%order%of%combinators%applied%ma4ers%for% performance • Ex:%Create%index%9tles%before%filtering • Some9mes%a%combinator%needs%to%implement%more% than%one%feature%for%performance ©"Robert"Brown"March"2015"@robby_brown
25. Example(Combinators • BaseDataSource:#Provides#minimum# func1onality • ChainableDataSource:#Allows#data#source# sequences • FilterableDataSource:#Allows#filtering#(ex.# search#bar) • ReorderableDataSource:#Allows#reordering • IndexableDataSource:#Shows#index#1tles ©"Robert"Brown"March"2015"@robby_brown
26. Demo ©"Robert"Brown"March"2015"@robby_brown
27. Summary 1. The&Hard&Way 2. Code&Architecture&Theory 3. The&Be7er&Way ©"Robert"Brown"March"2015"@robby_brown
28. Ques%ons? ©"Robert"Brown"March"2015"@robby_brown
29. Resources(to(Learn(More • Source(Code • Combinator • Func2onal(Programming(in(Swi7 • Func2onal(Snippets ©"Robert"Brown"March"2015"@robby_brown
30. Resources(to(Learn(More • Separa'on*of*Concerns • Cohesion • Orthogonality ©"Robert"Brown"March"2015"@robby_brown