I am loading new views for a small iphone app, and was wondering how to pass details from one to another?
I am loading a tableview full of data from and xml file, then once clicked a new view is brought in via:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
SubInfoViewController *subcontroller = [[SubInfoViewController alloc] initWithNibName:#"SubInfoView" bundle:nil];
[self presentModalViewController:subcontroller animated:YES];
[subcontroller release];
}
Next step would be to tell the newly loaded view which row had just been loaded?
Any idea, thoughts more than welcome, and please be gentle big newbie...
I typically create my own init method to do things like this. I think it would likely be better to pass in the corresponding "model" object represented by the tableView row, rather than the row number itself, like this:
In SubInfoViewController.h
#interface SubInfoViewController : UIViewController {
YourObject *yourObject;
}
#property (nonatomic, retain) YourObject *yourObject;
Then in SubInfoViewController.m:
- (SubInfoViewController*)initWithYourObject:(YourObject*)anObject {
if((self = [super initWithNibName#"SubInfoView" bundle:nil])) {
self.yourObject = anObject;
}
return self;
}
You'd create and present it this way:
// assuming you've got an array storing objects represented
// in the tableView called objectArray
SubInfoViewController *vc = [[SubInfoViewController alloc] initWithYourObject:[objectArray objectAtIndex:indexPath.row]];
[self presentModalViewController:vc animated:YES];
[vc release];
This could be adapted pretty easily to allow you to pass in any type of object or value (such as a row number if you still want to do that).
Add an instance variable to your view controller and declare a property corresponding to it, so after you alloc, init it, set it like subcontroller.foo = Blah Blah.
Related
I have a NSTableView where I wish to display a list of info.
Currently the viewForTableColumn method delegate never runs, but numberOfRowsInTableView does.
I have the NSTableViewDelegate and NSTableViewDataSource set in the ViewController head. And I set the tableview delegate and datasource to self. Does somebody know why it wouldn't run? I've added a screenshot and code below.
ViewController.h
#interface ViewController : NSViewController <NSTableViewDelegate, NSTableViewDataSource>
#property (strong) IBOutlet NSTableView *tableView;
#property (strong, nonatomic) NSMutableArray<App *> *installedApps;
#end
ViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
_installedApps = [[NSMutableArray alloc] init];
_tableView.dataSource = self;
_tableView.delegate = self;
// Other stuff that populates the array
}
- (NSInteger)numberOfRowsInTableView:(NSTableView *)tableView {
return _installedApps.count;
}
-(NSView *)tableView:(NSTableView *)tableView viewForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row {
NSTableCellView *result = [tableView makeViewWithIdentifier:#"appCell" owner:self];
result.textField.stringValue = #"Hello world";
return result;
}
The view is in a container view, I have the 'appCell' identifier set to the Table Cell View.
The array _installedApps is empty and numberOfRowsInTableView: returns 0. Thus, tableView:viewForTableColumn: is not called because there is no row to show. No rows also means no columns.
You should also ensure that you have configured your table view as view based in attributed inspector of the table view.
I can't see it in the screenshots, but...is the highlighted row of the view hierarchy (Table Cell View) the one with the appCell identifier?
[minutes pass...]
Oops; sorry. I see you've noted that above.
The reason I ask is that I made a new project from your code, changing the array type from App to NSString, added a one-column table view to the storyboard, linked it to the code, added a couple enties to the array in -viewDidLoad, and -- once I put the appCell identifier in the right place (duh) -- it all worked fine.
This is super strange, but I had the very same issue, everything connected correctly, number of rows being called, but not viewForTableColumn... In the end the following Answer proved to be the solution:
https://stackoverflow.com/a/13091436/3963806
Basically, I had setup the tableview straight out of the Object library, no layout constraints etc... Once I added layout constraints, the method started to be called... Super strange as I could see and click on the "rows" but they weren't populated correctly... I think it's down to clipping as mention in the linked answer.
I have a UITableView, named tblParentComments in a UIView, of class CBox.
I have definitely set my view as the datasource and delegate of my table view, and my view does implement those protocols. The method tableView:numberOfRowsInSection: does get called and returns a non-zero value. But the function tableView:cellForRowAtIndexPath: is never called.
I noticed that if I put the method tableView:cellForRowAtIndexPath: in comments, Xcode does NOT stop compiling with an error like "tableView:cellForRowAtIndexPath: is required" -- the app just runs and show a empty table.
I don't understand. Any ideas? This is the code for my view:
Interface CBox.h
#interface CBox : UIView <UITableViewDelegate, UITableViewDataSource>
And in the implementation file:
- (id) initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
tblParentComments = [[UITableView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, self.frame.size.width, frame.size.height)];
tblParentComments.delegate = self;
tblParentComments.dataSource = self;
//tblParentComments.userInteractionEnabled = NO;
tblParentComments.backgroundColor = [UIColor clearColor];
tblParentComments.separatorStyle = UITableViewCellSeparatorStyleNone;
tblParentComments.bounces = NO;
[self addSubview:tblParentComments];
}
return self;
}
#pragma mark - UITableViewDelegate + UITableViewDatasource
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
NSLog(#"num of rows = %d", parentComents.count);
return 1; // I set a non-zero value for test
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
.... // I set a breakpoint here, never been called here
}
YES..i have the same problem... and I just found out the solution.
In my class i use different inits with different parameters.
In my -(void)viewDidLoad i use to alloc the table view with CGRectZero, and ONLY in this case IF u DONT set up the FRAME of the UITableView then:
the numberOfRowsInSection will BE CALLED
the cellForRowAtIndexPath will NEVER BE CALL
I just set up my UITableView frame and it's works.
As I read above comments I can figure out couple of things:
You probably have messed up a bit structure of your code. You should always conform to protocols in your view controller - ! not view. Alternatively, what I like to do (as it gives me better control over my code and it keeps things clean), separate protocols out of view controller - means create new object (model object) that will handle everything what table requires and it will conforms to table delegate and datasource.
If you organise your code wisely, you should avoid situation you described.
Also I believe you may have 2 objects conforming to table protocols, and thats where the things get ugly.
I use the method performSegueWithIdentifier:sender: to open a new ViewController from a storyboard-file programmatically. This works like a charm.
But on every time when this method is being called, a new ViewController would be created. Is it possible to use the existing ViewController, if it exista? I don't find anything about this issue (apple-doc, Stack Overflow, ...).
The Problem is:
On the created ViewController the user set some form-Elements and if the ViewController would be called again, the form-elements has the initial settings :(
Any help would be appreciated.
Edit:
I appreciate the many responses. Meanwhile, I'm not familiar with the project and can not check your answers.
Use shouldPerforSegueWithIdentifier to either allow the segue to perform or to cancel the segue and manually add your ViewController. Retain a pointer in the prepareForSegue.
... header
#property (strong, nonatomic) MyViewController *myVC;
... implementation
-(BOOL) shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender{
if([identifier isEqualToString:#"MySegueIdentifier"]){
if(self.myVC){
// push on the viewController
[self.navigationController pushViewController:self.myVC animated:YES];
// cancel segue
return NO;
}
}
// allow the segue to perform
return YES;
}
-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"MySegueIdentifier"]){
// this will only be called the first time the segue fires for this identifier
// retian a pointer to the view controller
self.myVC = segue.destinationViewController;
}
}
To reuse an existing UIViewController instance with a segue create the segue from scratch and provide your own (existing) destination (UIViewController). Do not forget to call prepareForSegue: if needed.
For example:
UIStoryboardSegue* aSegue = [[UIStoryboardSegue alloc] initWithIdentifier:#"yourSegueIdentifier" source:self destination:self.existingViewController]
[self prepareForSegue:aSegue sender:self];
[aSegue perform];
Following code makes singleton view controller.
Add them to your destination view controller implementation, then segue will reuse the same vc.
static id s_singleton = nil;
+ (id) alloc {
if(s_singleton != nil)
return s_singleton;
return [super alloc];
}
- (id) initWithCoder:(NSCoder *)aDecoder {
if(s_singleton != nil)
return s_singleton;
self = [super initWithCoder:aDecoder];
if(self) {
s_singleton = self;
}
return self;
}
I faced this problem today and what I have done is to create the view controller manually and store it's reference.
Then every time I need the controller, check first if exists.
Something like this:
MyController *controller = [storedControllers valueForKey:#"controllerName"];
if (!controller)
{
controller = [[UIStoryboard storyboardWithName:#"MainStoryboard_iPhone" bundle:NULL] instantiateViewControllerWithIdentifier:#"MyControllerIdentifierOnTheStoryboard"];
[storedControllers setValue:controller forKey:#"controllerName"];
}
[self.navigationController pushViewController:controller animated:YES];
Hope it helps.
Create a property for the controller.
#property (nonatomic, weak) MyController controller;
And use some kind of lazy initialization in performSegueWithIdentifier:sender
if (self.controller == nil)
{
self.controller = [MyController alloc] init]
...
}
In this case, if controller was already created, it will be reused.
Firstly you would be going against Apple's design in Using Segues: "A segue always presents a new view controller".
To understand why it might help to know that what a segue does is create a new view controller and then the perform calls either showViewController or showDetailViewController depending on what kind of segue it is. So if you have an existing view controller just call those methods! e.g.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
Event *object = [self.fetchedResultsController objectAtIndexPath:indexPath];
self.detailViewController.detailItem = object;
[self showDetailViewController:self.detailViewController.navigationController sender:self];
}
You would need to make the Viewcontroller into a singleton class.
I have a Nav controller that starts at a table view. Each row pushes to a detail UIView. I would like to have a next and previous button on the Detail UIView that would show next and previous views without going back to parent UITableView. All details are saved in an array. how can i access that array and its current index in DetailViewController.m .Thanx in advance.
Another clean (and elegant) way is to build some sort of connection between the table view datasource, which is normally the UIViewController that contains the table, and the detail view: this can be done using the Delegate pattern, typical of Cocoa framework.
In such case you can define a DetailViewDataDelegate protocol with two methods only:
-(id)nextTableObjectFrom:(id)referenceObject;
-(id)prevTableObject;(id)referenceObject;
where referenceObject is the calling object, that is the object detailed in the DetailView.
So DetailView will be defined in this way:
#interface DetailViewController:UIViewController {
}
#property (nonatomic,assign) id currentDetailedObject;
#property (nonatomic,assign) id dataDelegate;
and of course when you call the controller, typical from the tableView:didSelectElementWithIndexPath:animated: method, you will do something like this:
DetailViewController *dv = [[[DetailViewController alloc] initWithNibName:nil bundle:nil] autorelease];
dv.dataDelegate=self;
dv.currentDetailedObject=[mySourceArray objectAtIndexPath:indexPath.row];
[self.navigationController pushViewController:dv animated:YES];
Finally in the DetailViewController when you need the next (or prev) element from the table you will simply call:
-(IBAction)nextButtonPressed {
self.currentDetailedObject = [self.dataDelegate nextTableObjectFrom:self.currentDetailedObject];
}
Of course the implementation details may change, and in particular the delegate methods, to be implemented in the table's UIViewController, will depend on the data structure.
The advantage of this approach, which can be at first sight complicated, is quite elegant and avoids to pass objects along controllers, which is often a source of memory issues. Besides with the delegate approach you can implement any complicated feature (e.g.: you can even manipulate table view objects directly from the DetailViewController, at your own risk of course!)
The cleanest way is to create a custom initializer for DetailViewController:
#interface DetailViewController : UIViewController
{
NSArray* allObjects;
NSUInteger displayedObjectIndex;
}
- (id) initWithObjectAtIndex: (NSUInteger) index inArray: (NSArray *) objects;
#end
#implementation DetailViewController
- (id) initWithObjectAtIndex: (NSUInteger) index inArray: (NSArray *) objects
{
self = [super initWithNibName:nil bundle:nil];
if ( self ) {
allObjects = [objects copy];
displayedObjectIndex = index;
}
return self;
}
#end
That way, a DetailViewController always knows both what object it is displaying details for and the previous/next objects, if any.
Hey guys, so in my newest program I use an NSTableView to display words on the left, and thier definitions on the right. these words and definitions are load from a .plist file, and at application startup the table view loads these words and definitions and displays them just fine. My problem comes in when the user tries to add a word and definition using the text boxes and buttons, the word is actually added to the .plist, meaning the method is running fine, but the table view refuses to display the new line. only until after i quit the program and reopen it does the tableview display the new line. I tested to see if the table view was connected properly by sending it other messages such as selectedRow and dataSource, all came back with responces, and proper responces at that. Currently the class that is used as the dataSource and delegate is a subclass to my main class with all my varibles and dictionaries. (I am big on using as little classes as possible). Lastly I tried inserting noteNumberOfRowsChanged in before reloadData, but still nothing.
I have tested everything and it just seems that the reloadData method is not initiating anything. Like I said, my table view is being sent the message, the new info is actually being added to the dicitinoary adn array, the amount of rows is being updated by the count method, and what proves it even more is that when the program is restarted it displays everything just fine. below is the relevent code, where currentWordList and currentDefitionList are the Array and Dictionary suppying the data to the dataSource, and editLibraryCardList is the NSTableView I am trying to reload.
the dataSource class code:
#interface EditorDataTable : SAT_Vocab_MacController {
IBOutlet NSTableColumn *editLibraryWordColumn;
IBOutlet NSTableColumn *editLibraryDefinitionColumn;
}
- (int)numberOfRowsInTableView:(NSTableView *)tableView;
- (id)tableView:(NSTableView *)tableView objectValueForTableColumn:(NSTableColumn *)tableColumn row:(int)row;
#end
#implementation EditorDataTable
- (int)numberOfRowsInTableView:(NSTableView *)tableView {
return ([currentWordList count]);
}
- (id)tableView:(NSTableView *)tableView objectValueForTableColumn:(NSTableColumn *)tableColumn row:(int)row {
if (tableColumn == editLibraryWordColumn) {
return [currentWordList objectAtIndex:row];
}
if (tableColumn == editLibraryDefinitionColumn) {
return [currentDefinitionList valueForKey:[[currentWordList objectAtIndex:row]lowercaseString]];
}
}
#end
method that adds the word to the list:
- (IBAction) editLibraryAddWordToLibrary: (id) sender {
if (self = [super init]) {
currentWordList = [[NSArray alloc] initWithContentsOfFile:userSATWordListPath];
currentDefinitionList = [[NSDictionary alloc] initWithContentsOfFile:userSATDefinitionListPath];
}
[currentWordList addObject:[[editLibraryNewCardWordInput stringValue]capitalizedString]];
[currentDefinitionList setObject:[editLibraryNewCardDefinitionInput stringValue] forKey:[[editLibraryNewCardWordInput stringValue]lowercaseString]];
aWordCounter = [currentWordList indexOfObject:[[editLibraryNewCardWordInput stringValue]capitalizedString]];
[aWordLabel setStringValue: [[NSString alloc] initWithFormat:#"%#", [currentWordList objectAtIndex: aWordCounter]]];
[aDefinitionLabel setStringValue: [[NSString alloc] initWithFormat:#""]];
[currentWordList writeToFile:userSATWordListPath atomically:YES];
[currentDefinitionList writeToFile:userSATDefinitionListPath atomically:YES];
[cardCountdownNumber setStringValue: [[NSString alloc] initWithFormat:#"%i", ([currentWordList count] - (1 + aWordCounter))]];
[editLibraryCardList noteNumberOfRowsChanged];
[editLibraryCardList reloadData];
}
Iv'e been stuck for days and any ideas will help! Thanks.
Zach
Have you tried debugging into your selectRowAtIndexPath method to make sure the reload occurs? (after you call [tableView reloadData] should be able to see this) Are you using UITableViewController?
If you wanted a callback after reload to know when its done, you could try:
[tableView reloadData];
[self performSelector:#selector(selectRowAtIndexPath:) withObject:indexPath afterDelay:0.0];
For those who are curious, i moved my code from the dataSource subclass to the main class, and it worked. i guess you cannot subclass the dataSource. Hope this helps!