Swift - iOS - Multiple table view controllers sharing a single data source.

Question

I'd like to get started using swift to make a small list based application. I was planning on using two table view controllers to display the two lists, and was wondering if it were possible to have them share a common data source.

Essentially the data would just be an item name, and two integers representing the amount of the item owned vs needed. When one number increases, the other decreases, and vice versa.

I figured this might be easiest to do using a single data source utilized by both table view controllers.

I did some googling on shared data sources and didn't find anything too useful to help me implement this. If there are any good references for me to look at please point me in their direction!

what's the difference between first and second table view controller ? You can use only one, and in cellForRowAtIndexPath method to check what cells you need to display for each cases in part — nsinvocation
– nsinvocation, Commented Aug 23, 2015 at 14:52
create as many table views as you want to and then just do things as you normally would but use a custom UITableViewCell and set a property for the custom cell to "owned" and "needed", in the tableview where you want to show the "owned" activate the owned property, in the tableview that you want to show the needed activate the needed property. subtract one from each other or repull from the server as necessary, that's it — Larry Pickles
– Larry Pickles, Commented Aug 23, 2015 at 15:00
Do you really want shared data source? You're introducing tight coupling between these view controllers that can cause maintenance issues in the future. You might share a model, but you generally wouldn't advise sharing data sources. — Rob
– Rob, Commented Aug 23, 2015 at 15:13
The only real difference between the first and second view controller would be the integer value being displayed in pair with the item name. For example: If an item is structured as so, (ItemName, Value1, Value2), then the first view controller would display: ItemName, Value2 while the second view controller would display: ItemName, Value1-Value2. — user5257412
– user5257412, Commented Aug 25, 2015 at 23:32

Evghenii Todorov · Accepted Answer · 2015-08-23 16:16:25Z

1

You can create one data source class and use it in both view controllers:

class Item {

}

class ItemsDataSource: NSObject, UITableViewDataSource {
    var items: [Item] = []

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        var cell = tableView.dequeueReusableCellWithIdentifier("cell") as! UITableViewCell

        //setup cell
        // ...

        return cell
    }

    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return items.count
    }
}

class FirstViewController : UITableViewController {
    var dataSource = ItemsDataSource()

    override func viewDidLoad() {
        self.tableView.dataSource = dataSource
        self.tableView.reloadData()
    }
}

class SecondViewController : UITableViewController {
    var dataSource = ItemsDataSource()

    override func viewDidLoad() {
        self.tableView.dataSource = dataSource
        self.tableView.reloadData()
    }
}

edited Aug 23, 2015 at 16:16

answered Aug 23, 2015 at 14:48

Evghenii Todorov

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3 Comments

Daniel Krom Over a year ago

this is not a single data source, it is two data sources from a class with the same name

Evghenii Todorov Over a year ago

You are right. If author needs only one data source object he can use a singleton.

bibscy Over a year ago

@EvgheniiTodorov do you work on freelance projects? If so, what's your hourly rate? Thanks

Daniel Krom · Accepted Answer · 2015-08-23 14:57:54Z

0

use singleton design pattern, it means both tables will get data source from the same instance

class sharedDataSource : NSObject,UITableViewDataSource{

    static var sharedInstance = sharedDataSource();
    override init(){
        super.init()
    }

    //handle here data source
    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int{

    }

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell{

    }


}

var tableOne = UITableView();
var tableTwo = UITableView();

tableOne.dataSource = sharedDataSource.sharedInstance;
tableTwo.dataSource = sharedDataSource.sharedInstance;

edited Aug 23, 2015 at 14:57

answered Aug 23, 2015 at 14:52

Daniel Krom

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4 Comments

nsinvocation Over a year ago

ugly solution to use singleton for providing data

Daniel Krom Over a year ago

@gottlieb explain why?

nsinvocation Over a year ago

Singleton can be access and modified everywhere in your program, it's ok for an utility/configuration class but not for a data-providing class. It creates a hidden dependency between different INDEPENDENT program modules, which makes code harder to read and debug, and is a source of bugs.

Daniel Krom Over a year ago

I disagree, I think you are confusing between data provider and data storage. anyway if you have an article that approves that i'd like to read that

channu · Accepted Answer · 2019-08-07 12:37:08Z

0

The first argument to the delegate method is:

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
}

At that point, your one Datasource delegate can decide which table view is wanting a cell, for example, and return results accordingly.

edited Aug 7, 2019 at 12:37

channu

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answered Aug 23, 2015 at 14:53

gnasher729

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