Data Source Combinators
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This document discusses improving table view data sources by implementing the single responsibility principle and using combinators. It outlines problems with traditional approaches where view controllers handle data sources and cells. The author advocates defining base data source classes that provide minimal functionality and combining them to add dynamic behaviors like filtering, reordering and indexing. Implementing this approach removes duplicate code, allows changing behavior through combinators, and makes data sources reusable across views. Examples of combinators that could be implemented are provided.
![Cell$Crea'on
class CandyTableViewController : UITableViewController {
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.candies.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
let candy = self.candies[indexPath.row]
cell.textLabel!.text = candy.name
cell.accessoryType = UITableViewCellAccessoryType.DisclosureIndicator
return cell
}
}
From:&raywenderlich.com
息"Robert"Brown"March"2015"@robby_brown](https://image.slidesharecdn.com/datasourcecombinators-150402143804-conversion-gate01/85/Data-Source-Combinators-6-320.jpg)
![Cell$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)
}
}
息"Robert"Brown"March"2015"@robby_brown](https://image.slidesharecdn.com/datasourcecombinators-150402143804-conversion-gate01/85/Data-Source-Combinators-19-320.jpg)
![Cell$Crea'on
View%Controller
override func viewDidLoad() {
super.viewDidLoad()
let objects = [] // Get objects here
let base = BaseDataSource(objects) { (view, indexPath, object) -> Any in
return MyCell.cell(view as! UITableView, name: object as! String)
}
self.dataSource = ReorderableDataSource(base)
}
息"Robert"Brown"March"2015"@robby_brown](https://image.slidesharecdn.com/datasourcecombinators-150402143804-conversion-gate01/85/Data-Source-Combinators-20-320.jpg)
Data Source Combinators
- 3. Overview 1. The&Hard&Way 2. Code&Architecture&Theory 3. The&Be7er&Way 息"Robert"Brown"March"2015"@robby_brown
- 6. Cell$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 息"Robert"Brown"March"2015"@robby_brown
- 7. Cell$Crea'on What's'wrong'with'this? Duplicate+boilerplate View+controllers+handle+interac5on,+not+data+sources Cells+are+o8en+shared+between+table+views Cells+should+handle+their+own+layout 息"Robert"Brown"March"2015"@robby_brown
- 8. Cell$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 息"Robert"Brown"March"2015"@robby_brown
- 12. Data$Sources Solu%on: Single(responsibility0principle Combinators Chain(of(responsibility 息"Robert"Brown"March"2015"@robby_brown
- 16. Combinators Technique*from*func/onal*programming Usually*seen*with*parsers Generally*represent*a*single,*simple*feature Focus*on*composi/on Like*higher>order*func/ons*applied*to*features 息"Robert"Brown"March"2015"@robby_brown
- 17. Chain&of&Responsibility Like&a&chain&of&delegates A&3>&B&3>&C&3>&D&... If&A&can't&handle&something,&then&try&B&... Used&to&create&a&sequence&of&combinators 息"Robert"Brown"March"2015"@robby_brown
- 19. Cell$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) } } 息"Robert"Brown"March"2015"@robby_brown
- 20. Cell$Crea'on View%Controller override func viewDidLoad() { super.viewDidLoad() let objects = [] // Get objects here let base = BaseDataSource(objects) { (view, indexPath, object) -> Any in return MyCell.cell(view as! UITableView, name: object as! String) } self.dataSource = ReorderableDataSource(base) } 息"Robert"Brown"March"2015"@robby_brown
- 21. Cell$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 } } 息"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 息"Robert"Brown"March"2015"@robby_brown
- 23. Dynamic(Behaviors Array Mul)*dimensional2array Filtering Reordering Edi)ng Index2)tles 息"Robert"Brown"March"2015"@robby_brown
- 24. Considera*ons The%order%of%combinators%applied%ma4ers%for%performance Ex:%Create%index%9tles%before%鍖ltering Some9mes%a%combinator%needs%to%implement%more%than%one% feature%for%performance 息"Robert"Brown"March"2015"@robby_brown
- 25. Example(Combinators BaseDataSource:#Provides#minimum#func1onality ChainableDataSource:#Allows#data#source#sequences FilterableDataSource:#Allows#鍖ltering#(ex.#search#bar) ReorderableDataSource:#Allows#reordering IndexableDataSource:#Shows#index#1tles 息"Robert"Brown"March"2015"@robby_brown
- 27. Summary 1. The&Hard&Way 2. Code&Architecture&Theory 3. The&Be7er&Way 息"Robert"Brown"March"2015"@robby_brown
- 29. Resources(to(Learn(More Source(Code Combinator Func2onal(Programming(in(Swi7 Func2onal(Snippets 息"Robert"Brown"March"2015"@robby_brown
- 30. Resources(to(Learn(More Separa'on*of*Concerns Cohesion Orthogonality 息"Robert"Brown"March"2015"@robby_brown