Setting a NSString to the sending end of a segue - iphone

Question

I made a simple project to explain my problem. Basically what I did was make a project with the templet of a Master Detail Application. Then in the
DetailViewController.h
nothing
DetailViewController.m
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"showDetail"])
{
[segue.destinationViewController setCellName2:#"New String"];
}
}
MasterViewController.h
#property(nonatomic,strong) NSString *cellName2;
MasterViewController.m
#synthesize cellName2;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSLog(#"%#", cellName2);
}
My problem is in the detailViewController where I set the cellName2, I cant set it because the detailViewController is the receivingViewController of the segue. Is their a method to set the sendingViewController end of a segue?
Edit
After Firo's answer my code looks like this now
MasterViewContoller.h
#import <UIKit/UIKit.h>
#import "DetailViewController.h"
#interface MasterViewController : UITableViewController <DetailViewDelegate>
#property(nonatomic,strong) NSString *cellName2;
#end
.m
#import "MasterViewController.h"
#import "DetailViewController.h"
#interface MasterViewController () {
NSMutableArray *_objects;
}
#end
#implementation MasterViewController
#synthesize cellName2;
- (void)awakeFromNib
{
[super awakeFromNib];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.navigationItem.leftBarButtonItem = self.editButtonItem;
UIBarButtonItem *addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:#selector(insertNewObject:)];
self.navigationItem.rightBarButtonItem = addButton;
self.cellName2 = cellName;
NSLog(#"%#", self.cellName2);
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)insertNewObject:(id)sender
{
if (!_objects) {
_objects = [[NSMutableArray alloc] init];
}
[_objects insertObject:[NSDate date] atIndex:0];
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
[self.tableView insertRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
}
#pragma mark - Table View
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return _objects.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"Cell" forIndexPath:indexPath];
NSDate *object = _objects[indexPath.row];
cell.textLabel.text = [object description];
return cell;
}
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
// Return NO if you do not want the specified item to be editable.
return YES;
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
[_objects removeObjectAtIndex:indexPath.row];
[tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationFade];
} else if (editingStyle == UITableViewCellEditingStyleInsert) {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view.
}
}
/*
// Override to support rearranging the table view.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
}
*/
/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
// Return NO if you do not want the item to be re-orderable.
return YES;
}
*/
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if([segue.identifier isEqualToString:#"showDetail"]) {
/* assigning self as delegate, telling the detail view that I implement
* setCellName2:, so it (the detailVC) can call it whenever it wants to.
*/
[segue.destinationViewController setDelegate:self];
}
}
// my implementation of the DetailViewDelegate protocol that I abide to
/* note: #pragma mark is not required, just for comment, documentation
* and find-ability purposes
*/
//#pragma mark - DetailViewDelegate
// note: this is just a property setter so this is not actually needed
//- (void)setCellName2:(NSString *)cellName {
// self.cellName2 = cellName;
// NSLog(#"%#", self.cellName2);
//}
#end
DetailViewContoller.h
#import <UIKit/UIKit.h>
/* defining a protocol, whoever is a DetailViewDelegate must implement my
* defined methods
*/
#protocol DetailViewDelegate <NSObject>
- (void)setCellName2:(NSString *)cellName;
#end
#interface DetailViewController : UIViewController
/* storing a delegate property. Whoever sets themselves to my delegate
* must implement my DetailViewDelegate's methods (setCellName2: in this case)
*/
#property (weak, nonatomic) id<DetailViewDelegate> delegate;
#property (strong, nonatomic) id detailItem;
#property (weak, nonatomic) IBOutlet UILabel *detailDescriptionLabel;
#end
.m
#import "DetailViewController.h"
#interface DetailViewController ()
- (void)configureView;
#end
#implementation DetailViewController
#pragma mark - Managing the detail item
- (void)setDetailItem:(id)newDetailItem
{
if (_detailItem != newDetailItem) {
_detailItem = newDetailItem;
// Update the view.
[self configureView];
}
}
- (void)configureView
{
// Update the user interface for the detail item.
if (self.detailItem) {
self.detailDescriptionLabel.text = [self.detailItem description];
}
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
//[self.delegate setCellName2:#""];
[self configureView];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"showDetaila"])
{
[segue.destinationViewController setCellName2:#"New String"];
}
}
#end
The problem now is, i am getting the error "Use of undeclared identifier 'cellName'; did you mean 'cellName2'?"

Answer 1

You are looking for delegates and protocols. Since you are not segueing from your detailVC to your masterVC you cannot put this setter in prepareForSegue. You need to store a reference to the master and have callbacks to it. Here is how you would do it with your basic example:
DetailViewController.h
/* defining a protocol, whoever is a DetailViewDelegate must implement my
* defined methods
*/
#protocol DetailViewDelegate <NSObject>
- (void)setCellName2:(NSString *)cellName;
#end
#interface DetailViewController : UIViewController
/* storing a delegate property. Whoever sets themselves to my delegate
* must implement my DetailViewDelegate's methods (setCellName2: in this case)
*/
#property (weak, nonatomic) id<DetailViewDelegate> delegate;
#end
DetailViewController.m
#implementation DetailViewController
// some action or method
- (IBAction)buttonPress:(id)sender {
// look below at Master's prepareForSegue
/* calling the method that my delegate implements, my delegate can be any
* object that implements my protocol (DetailViewDelegate)
*/
[self.delegate setCellName2:#""];
}
#end
MasterViewController.h
#import "DetailViewController.h"
// saying I implement the DetailViewDelegate protocol (and all necessary methods)
#interface MastViewController : UITableViewController <DetailViewDelegate>
#end
MasterViewController.m
#interface MasterViewController ()
#property(strong, nonatomic) NSString *cellName2;
#end
#implementation MasterViewController
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
if([segue.identifier isEqualToString:#"showDetail"]) {
/* assigning self as delegate, telling the detail view that I implement
* setCellName2:, so it (the detailVC) can call it whenever it wants to.
*/
[segue.destinationViewController setDelegate:self];
}
}
// my implementation of the DetailViewDelegate protocol that I abide to
/* note: #pragma mark is not required, just for comment, documentation
* and find-ability purposes
*/
#pragma mark - DetailViewDelegate
// note: this is just a property setter so this is not actually needed
- (void)setCellName2:(NSString *)cellName {
_cellName = cellName
NSLog("%#", self.cellName);
}
#end
I would give you some more information about delegates and protocols but it is an extremely common pattern when dealing with iOS development. You also should become extremely familiar with delegates and protocols, you will find it useful in many situations and it will help you better understand iOS development and make you a more competent programmer. If something does not work (or make sense) let me know. I just typed this up in SO so there could be some mild mistakes.
Edit
Note: If this becomes to far from the original question you may need to just create a new one.
Your main issue here is that you have self.cellName2 = cellName; in your MasterViewController. According to your original post you want the DetailVC to set this, right? So it will need to go into DetailViewController's viewDidLoad:
- (void)viewDidLoad {
[super viewDidLoad];
[self.delegate setCellName2:#"My custom text!"];
}
Then remove:
self.cellName2 = cellName;
NSLog(#"%#", self.cellName2);
From your MasterViewController's viewDidLoad. Your error is with the first line there (I am assuming). What is cellName? It is not a string and you have not defined it as a variable or property, hence the error.

Answer 2

Are you sure that the code is in the right class? And that you have the segues hooked up correctly in the storyboard?
In your DetailViewController code, you indicate that the segue identifier is "showDetail". It would seem to me that you ought to be handling that in your MasterViewController, as the pattern is typically that MasterViewController is responsible for seguing to the DetailViewController for the purpose of showing details.
Basically, if the destinationViewController property of the segue is NOT an instance of MasterViewController, then either the segue is not correctly configured or your code is in the wrong place.
If I'm mistaken please post more code.