I am working on this couple of days and I can't figure out what I am doing wrong.
First, I don't know if the KVO is the best way to pass the value of the clicked row info from one view controller to another view controller.
I have Main view, with 2 buttons only. Clicking on one of the buttons, I open MasterTableViewController, where I have the NSTableView with some records (one column only) from core data.
On click on the NSTableView, I am opening the DetailViewController, where I have only one label.
What I am trying is to change the label value, with the value of the clicked row in the NSTableView.
While I can print the value of the clicked row in the DetailViewController, I can't change the label value. I assume that notification comes before the viewDidLoad get called.
I have the following code:
In my MasterTableViewController.h file:
#import <Cocoa/Cocoa.h>
#import "AppDelegate.h"
@interface MasterTableViewController : NSViewController
@property (nonatomic,strong) NSManagedObjectContext *mObjContext;
@property (weak) IBOutlet NSTableView *websitesTableView;
- (IBAction)tableViewDoubleClick:(id)sender;
@property (nonatomic,strong) NSString *cellValue;
@end
In my MasterTableViewController.m file:
#import "MasterTableViewController.h"
#import "DetailViewController.h"
@interface MasterTableViewController ()
@end
@implementation MasterTableViewController
-(void)awakeFromNib {
[_websitesTableView setTarget:self];
[_websitesTableView setDoubleAction:@selector(tableViewDoubleClick:)];
}
- (void)viewDidLoad {
[super viewDidLoad];
// Get the object managed context
AppDelegate *appDelegate = (AppDelegate*)[[NSApplication sharedApplication] delegate];
self.mObjContext = appDelegate.managedObjectContext;
}
- (IBAction)tableViewDoubleClick:(id)sender {
NSInteger rowNumber = [_websitesTableView clickedRow];
NSTableColumn *column = [_websitesTableView tableColumnWithIdentifier:@"websiteUrl"];
NSCell *cell = [column dataCellForRow:rowNumber];
_cellValue = [cell stringValue];
MasterTableViewController *mtvc = [[MasterTableViewController alloc]initWithNibName:@"MasterTableViewController" bundle:nil];
DetailViewController *dvc = [[DetailViewController alloc]initWithNibName:@"DetailViewController" bundle:nil];
[mtvc addObserver:dvc
forKeyPath:@"cellValue"
options:NSKeyValueObservingOptionNew
context:NULL];
[mtvc setCellValue:_cellValue];
[mtvc removeObserver:dvc forKeyPath:@"cellValue"];
AppDelegate *appDelegate = (AppDelegate*)[[NSApplication sharedApplication] delegate];
[appDelegate changeViewController:2];
}
@end
Code for the DetailViewController.h is:
#import <Cocoa/Cocoa.h>
#import "AppDelegate.h"
@interface DetailViewController : NSViewController
@property (nonatomic, weak) AppDelegate *appDelegate;
@property (weak) IBOutlet NSTextField *detailLabel;
@property (nonatomic,strong) NSString *transferedLabelValue;
@property (nonatomic,strong) NSString *cellValue;
@end
Code for the DetailViewController.m is:
#import "DetailViewController.h"
#import "MasterTableViewController.h"
@interface DetailViewController ()
@end
@implementation DetailViewController
- (void)viewDidLoad {
[super viewDidLoad];
// if I uncomment this line, program crashes, because the value of the _transferedLabelValue is null here.
//[_detailLabel setStringValue:_transferedLabelValue];
}
-(void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary *)change
context:(void *)context {
if ([keyPath isEqualToString:@"cellValue"]) {
_transferedLabelValue = [change objectForKey:NSKeyValueChangeNewKey];
// Here I get the value of the clicked cell, it is printed in the console. However if I try to change the label value here, doesn't work, since seems that label does not exist yet at this point....
NSLog(@"Value in the observerValueForKeyPath is:%@",_transferedLabelValue);
}
}
@end
Code from the AppDelegate.h :
#import <Cocoa/Cocoa.h>
@interface AppDelegate : NSObject <NSApplicationDelegate>
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (weak) IBOutlet NSView *mainAppView;
@property (nonatomic,strong) NSViewController *mainAppViewController;
- (IBAction)showMasterViewButtonHasBeenClicked:(id)sender;
- (IBAction)showDetailViewButtonHasBeenClicked:(id)sender;
- (void)changeViewController:(NSInteger)tag;
@end
Here is only the relevant code from the AppDelegatge.m, the boiler plate code is omited.
#import "AppDelegate.h"
#import "MasterTableViewController.h"
#import "DetailViewController.h"
@interface AppDelegate ()
@property (weak) IBOutlet NSWindow *window;
- (IBAction)saveAction:(id)sender;
@end
@implementation AppDelegate
- (IBAction)showMasterViewButtonHasBeenClicked:(id)sender {
NSInteger tag = [sender tag];
[self changeViewController:tag];
}
- (IBAction)showDetailViewButtonHasBeenClicked:(id)sender {
NSInteger tag = [sender tag];
[self changeViewController:tag];
}
- (void)changeViewController:(NSInteger)tag {
[[_mainAppViewController view]removeFromSuperview];
switch (tag) {
case 1:
self.mainAppViewController = [[MasterTableViewController alloc]initWithNibName:@"MasterTableViewController" bundle:nil];
[_mainAppView addSubview:[_mainAppViewController view]];
[[_mainAppViewController view] setFrame:[_mainAppView bounds]];
[[_mainAppViewController view] setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
break;
case 2:
self.mainAppViewController = [[DetailViewController alloc]initWithNibName:@"DetailViewController" bundle:nil];
[_mainAppView addSubview:[_mainAppViewController view]];
[[_mainAppViewController view] setFrame:[_mainAppView bounds]];
[[_mainAppViewController view] setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
break;
}
}
Again, if the KVO and notification is not the best way to go, please let me know how I should "inform" the other view which row has been clicked and which is his value.
Regards, John
I manage to solve my problem with the KVO...My problem was that I was creating new instances of the view controllers in the MasterTableViewController...What I did was I created properties for the ViewControllers in the appDelegatge.h like this:
@property MasterTableViewController *mtvc;
@property DetailViewController *dvc;
and then in the appDelegate.m :
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
_mtvc = [[MasterTableViewController alloc]initWithNibName:@"MasterTableViewController" bundle:nil];
_dvc = [[DetailViewController alloc]initWithNibName:@"DetailViewController" bundle:nil];
}
Rest of the changes in the code are just replacing the MasterTableViewController and DetailViewController with _mtvc and _dvc...
However...I had been warned that this solution is error prone, and that warning shows true. It happens from time to time that I get wrong value, not the clicked one. Once in 4-5 clicks, I get wrong value. What makes me confuse is that I make the function to work on double click, but it works on single click as well...But those things are for some other question I guess.