Communiacting between UIDatePicker and UITableView

Question

In my project I have 3 controllers;

• NavigationController
• ServiceTableViewController
• DateTableViewController

The ServiceTableViewController is the initial view controller. It has several rows which prompt the user to enter in data, which will be emailed to a particular email address. One of the rows, when tapped, sends the user to the DateTableViewController which prompts the user to select a date from the UIDatePicker.

The issue I am facing is getting data back from DateTableViewController in order to display a label on the ServiceTableViewController to show the date the user selects in the DateTableViewController. I know how to get information from one view controller to another, but to go in reverse, so to speak, is not something I know how to do. Any help is appreciated.

Answer 1

Research delegate pattern (here) (a heavily used pattern within Apple frameworks). You want to define a delegate protocol which allows to a date to be passed to the delegate.

You could implement the pattern as an @protocol with a single method and a property on the DateTableViewController. The ServiceTableViewController sets itself as the delegate before pushing the DateTableViewController.

Or, you could implement using a block. Again, the ServiceTableViewController sets the block before pushing the DateTableViewController.

Answer 2

Take a look at this: https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CocoaFundamentals/CommunicatingWithObjects/CommunicateWithObjects.html

There are couple of ways to pass data back and forth between view controllers.

• Delegates
• Target-Aciton
• Notification
• KVO

but honestly delegates are really all you need really and it sounds like in your current case. see this -> (Passing Data between View Controllers)

---

Having said that, if you use delegates, here is how --- setup a protocol in DateTableViewController.h at the top like so:

@protocol DateTableViewControllerDelegate <NSObject>
- (void)userSelectedThisDate:(NSDate *)d;
end

put this with the other properties

@property (nonatomic, weak) id <DateTableViewControllerDelegate> delegate;

and in DateTableViewController.m with the date to send back

[self.delegate userSelectedThisDate:withTheDateToSendBack];

in and ServiceTableViewController.h add

#import "DateTableViewController.h"
@interface ServiceTableViewController : UIViewController <DateTableViewControllerDelegate>

and since you are UINavigationController, somewhere in ServiceTableViewController.m add this when you are about to push to the DateTableViewController

DateTableViewController *vc = [[DateTableViewController alloc] init];
self.delegate = self;
[self.navigationController pushViewController:vc animated:YES];

and finally put the delegate method in ServiceTableViewController.m

- (void)userSelectedThisDate:(NSDate *)d {
   NSLog(@"%@", d); // this should show the returned date 
}