CODEWITHSUNDEEP
c#uiviewcontrollerxamarin.ios
banzai86
banzai86

Reputation: 747

Monotouch: send data back down the stack to another ViewController

I have a question concerning Monotouch.

The situation: I have 2 ViewControllers. The first (let's call it VC-A) looks similar to the contacts edit screen, meaning it has a TableView with multiple Sections each containing Buttons and TextFields. Now when the user clicks one of these Buttons, he will get to the second ViewController (VC-B), which displays a TableView containing data from the database. When the user clicks on any of these rows, VC-B will be closed and i want to display the selected database entry (string) as the title of the Button (in VC-A) which opened VC-B in the first place.

When I did an objective-C project last year, I managed to send data back down the stack by using delegates, but I haven't found a way yet how this works in Monotouch.

I have read several questions here on SO about using the AppDelegate or using singletons, but I'm not sure that this is the right way of returning data from a subview.

Upvotes: 2

Views: 1110

Answers (3)

Anuj
Anuj

Reputation: 3134

I actually prefer to use TinyMessenger for cross container calls I find this to be very very useful when you don't want to keep references to your heavy viewcontrollers around which could potentially result in memory leaks!

var messageHub = new TinyMessengerHub();
// Publishing a message is as simple as calling the "Publish" method.
messageHub.Publish(new MyMessage());

// We can also publish asyncronously if necessary
messageHub.PublishAsync(new MyMessage());

// And we can get a callback when publishing is completed
messageHub.PublishAsync(new MyMessage(), MyCallback); 
// MyCallback is executed on completion

https://github.com/grumpydev/TinyMessenger

Upvotes: 0

Krumelur
Krumelur

Reputation: 33058

You can kind of copy the delegate pattern. Add a C# delegate to your VC-B that takes one parameter, some data structure. In VC-B's "ViewWillDisappear", call the delegate it it is not null and pass the data on to it. This way, your calling VC can get acces to the data but you don't need tight coupling between the two controllers. All it has to do, is register a delegate-method in VC-B.

As MonoTouch is .NET4 you can use Func<MyDataStructure> or Action<MyDataStructure> and don't need to use full qualified delegate types.

Upvotes: 5

Jason
Jason

Reputation: 89169

I have a static singleton class that I use to store "state" type data about my app - current settings and selections that are needed in many different places in the app. That's one way to approach this.

You could also pass VC-B a reference to VC-A when you create VC-B, so that it can explicitly access it's parent view and pass back values that way.

Upvotes: 2

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