iOS Question
Separating Data Source to another class in Swift
I'm trying to keep my view controllers clean as described in this article objc.io Issue #1 Lighter View Controllers. I tested this method in Objective-C and it works fine. I have a separate class which implements
UITableViewDataSource#import "TableDataSource.h"
@interface TableDataSource()
@property (nonatomic, strong) NSArray *items;
@property (nonatomic, strong) NSString *cellIdentifier;
@end
@implementation TableDataSource
- (id)initWithItems:(NSArray *)items cellIdentifier:(NSString *)cellIdentifier {
self = [super init];
if (self) {
self.items = items;
self.cellIdentifier = cellIdentifier;
}
return self;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return self.items.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:self.cellIdentifier forIndexPath:indexPath];
cell.textLabel.text = self.items[indexPath.row];
return cell;
}
@end
From the tableview controller, all I have to do is instantiate a instance of this class and set it as the tableview's data source and it works perfectly.
self.dataSource = [[TableDataSource alloc] initWithItems:@[@"One", @"Two", @"Three"] cellIdentifier:@"Cell"];
self.tableView.dataSource = self.dataSource;
Now I'm trying to do the same in Swift. First here's my code. Its pretty much of a translation of the Objective-C code above.
import Foundation
import UIKit
public class TableDataSource: NSObject, UITableViewDataSource {
var items: [AnyObject]
var cellIdentifier: String
init(items: [AnyObject]!, cellIdentifier: String!) {
self.items = items
self.cellIdentifier = cellIdentifier
super.init()
}
public func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return items.count
}
public func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier(cellIdentifier, forIndexPath: indexPath) as UITableViewCell
cell.textLabel?.text = items[indexPath.row] as? String
return cell
}
}
And I call it like this.
let dataSource = TableDataSource(items: ["One", "Two", "Three"], cellIdentifier: "Cell")
tableView.dataSource = dataSource
But the app crashes with the following error.
-[NSConcreteNotification tableView:numberOfRowsInSection:]: unrecognized selector sent to instance
I checked the
initTableDataSourceUITableViewDataSourcepublicoverrideI'm clueless on what's going wrong here. Can anyone please help me out?
Thank you.
Answer
Create a property for data source and use it with your tableview.
class ViewController: UIViewController {
@IBOutlet weak var tableView: UITableView!
var dataSource:TableDataSource!
override func viewDidLoad() {
super.viewDidLoad()
dataSource = TableDataSource(items: ["One", "Two", "Three"], cellIdentifier: "Cell")
tableView.dataSource = dataSource
}
}
Source (Stackoverflow)