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Passing data between view controllers
(45 answers)
Closed 8 years ago.
I have a Assignment ViewController and a TableViewController.
The assignment View Controller takes input and saves the information in an object.
What I need is , using delegation, alert the tableviewcontroller that an assignment was created, and have the tableviewcontroller add the object to a NSMutableArray, and archive it.
It seems easy but I am having a hard time understanding delegation.
Here is the save Method - AssignmentViewController.m :
- (IBAction)Save:(UIButton *)sender {
self.homeworkAssignment = [[Homework alloc] init];
self.homeworkAssignment.className = self.ClassNameField.text;
self.homeworkAssignment.assignmentTitle = self.AssignmentTitleField.text;
self.homeworkAssignment.assignmentDiscription = self.DiscriptionTextView.text;
self.homeworkAssignment.pickerDate = self.DatePicker.date;
NSMutableArray *MyHomeworkArray = [[NSMutableArray alloc] init];
[MyHomeworkArray addObject:self.homeworkAssignment];
NSString *filePath = [self dataFilePath];
//Archive my object
[NSKeyedArchiver archiveRootObject:MyHomeworkArray toFile:filePath];
}
My save method currently saves the info, adds to an array, and archives. But I need to use delegation between my TableViewController and my AssignmentViewController, and have my tableViewCOntroller alerted when save is pressed, and then add to the array and archive it itself.
Can someone please help me set this up correctly using delegation?
Add property for your array in UITableViewController:
#property (nonatomic,retain) NSMutableArray *homeworkArray;
now on save method:
-(IBAction)Save:(UIButton *)sender {
UITableViewController *tabVC = [[UITableViewController alloc] init];
tableVC.homeworkArray = self. MyHomeworkArray; // send a message to tableview
[self.navigationcontroller pushViewController:tableVC];
}
Now in TableViewController you need to set override your datasource method to show text on cell
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [self.homeworkArray count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
// Configure the cell...
if(!cell){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
//update your cell here
cell.textLabel.text = self.homeworkAssignment.className
cell.detailTextLabel.text = self.AssignmentTitleField.text;
return cell;
}
Related
I have two UITableViewController classes, MainTableController and SubTableController.
From AppDelegate class I am calling MainTableController class.
At first this class is empty, and there is button named "show list" in this class.
When I click on this button I will go to SubTableController and there I have a list of actions in form of table.
Now if I choose to first cell action then that action name has to come on my first cell of table in MainTableController. But I am not able to print that name in table of MainTableController class.
In SubTableController:
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
ActionList * actionListObj = [appDelegate.actionArray objectAtIndex:indexPath.row];
self.chooseActions = actionListObj.actionName;
MainTableController * mainViewController = [[MainTableController alloc] init];
[mainViewController getAction:self.chooseActions];
[self.navigationController dismissModalViewControllerAnimated:YES];
}
In MainTableController:
-(void) viewWillAppear:(BOOL)animated{
[self reloadData];
}
-(void) reloadData{
[self.myTableView reloadData];
}
-(void) getAction: (NSString *) actionChoose{
self.action = actionChoose;
[self reloadData];
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
// Configure the cell...
cell.textLabel.text = self.action;
return cell;
}
When I debug, in MainTableController I am getting the action in getAction method but in table cell text string is null.
Can anyone please help me regarding this?Where am I going wrong?
You are allocating and initializing a new view controller each time you select a cell in SubTableController.
MainTableController * mainViewController = [[MainTableController alloc] init];
and of course, it isn't the one in place in the navigation stack.
You need to make these two controllers communicate.
I suggest that the sub view controller define a property on the main one, in order to message it when needed.
In SubTableController, add a property and synthesize it :
#property(readwrite, assign) MainViewController *mainViewController;
// and ...
#synthesize mainViewController;
Of course when you push the sub view controller, don't forget to set the property.
// in main view controller
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// alloc/init the sub VC
subVCInstance.mainViewController = self;
[self pushViewController:subVCInstance ......
Now when a row is selected in the sub one, message the main one, without alloc/init a new MainViewController object :
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
ActionList * actionListObj = [appDelegate.actionArray objectAtIndex:indexPath.row];
self.chooseActions = actionListObj.actionName;
//MainTableController * mainViewController = [[MainTableController alloc] init];
[self.mainViewController getAction:self.chooseActions];
[self.navigationController dismissModalViewControllerAnimated:YES];
}
This should work just fine.
In didSelectRowAtIndexPath of the SubTableController class, you are allocating new MainTableController to send the data.
MainTableController * mainViewController = [[MainTableController alloc] init];
[mainViewController getAction:self.chooseActions];
You should not do like that. Because the existing mainview will be different from the newly allocated one. You should use delegate to give back the data. For more info on Protocols and delegates, see here
More example here
I am facing a crashing problem in cellForRowAtIndexPath tableview delegate method
#interface EventListView : UIViewController <UITableViewDelegate, UITableViewDataSource>
IBOutlet UITableView *tblView;
NSMutableArray *arr_EventValues,*arr_Event_Details;
NSMutableArray *arr_EventListDetails;
#property(nonatomic, retain)NSMutableArray *arr_EventValues,*arr_EventListDetails, *arr_Event_Details;
#property(nonatomic, retain)UITableView *tblView;
- (void)viewDidLoad
{
appdelegate = (VibesGuideAppDelegate *)[[UIApplication sharedApplication] delegate];
ViewCalendar = [[CalendarView alloc] initWithNibName:#"CalendarView" bundle:[NSBundle mainBundle]];
[self.navigationController.navigationBar setHidden:YES];
self.arr_Event_Details = [[NSMutableArray alloc] init];
self.arr_EventValues = [[NSMutableArray alloc] init];
[super viewDidLoad];
}
// Customize the number of sections in the table view.
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
// Customize the number of rows in the table view.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
if ([self.arr_EventListDetails count] > 0)
{
return [self.arr_EventListDetails count];
}
return 0;
}
-(UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
// ------------------------------- Custom cell ------------------------------
Customcell *cell = (Customcell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
cell = [[[Customcell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
cell.textLabel.text = #"Hello";
return cell;
}
* -[EventListView tableView:cellForRowAtIndexPath:]: message sent to deallocated instance 0x60e01b0 and I used tableview from xib and set all connections and also got arrayvalues in numberOfRowsInSection in method but in cellForRowAtIndexPath method is not called so please give me idea my issue....
Thanks in advance.
At first it seems your some variable gets released. Make sure you have properly allocated it. If you have declared #property for it you better use the variable as self.variable. You can use retain and in case of IOS 5 strong in property declaration.
Just to be sure you can track if any variable gets released via setting NSZombieEnabled to YES. With zombies enabled, messages to deallocated objects will no longer behave strangely or crash in difficult-to-understand ways, but will instead log a message and die in a predictable and debugger-breakpointable way. You can set NSZombieEnabled by the following steps.
Select Product from the menu bar above. Keep alt/option pressed and select "Test..." or "Run...". Go to the Arguments tab, and add NSZombieEnabled YES in the "Environment Variables" section.
Your tableview itself is already released - the error message says that you send the cellForRowAtIndexPath message to a deallocated instance of the table view - so your problem lies somewhere in not retaining or releasing the EventListView and cannot be seen in the code displayed here.
Check this one:
Table DataSource and delegate is set or not.
Used array in cellForRowAtIndexPath is properly set with property and synthesized as well used with self. name.
First of all you dequeue the cell and then create a new one. This is not a good practice, if you are able to dequeue a cell you should not create a new one. You should have something like this:
Customcell *cell = (Customcell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if(cell == nil)
{
cell = [[[Customcell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
}
fix this and let me know if you are still running on the same problem.
I am trying to feed in some JSON data to my iPhone app, the data is coming in fine as I have NSLog's telling me so.
The problem I am having is trying to get the results to show in a UITableView. I have a navigation controller underneath a tab bar controller, the navigation controller contains a table view controller which loads another NIB file with a table view connected to a class which is the delegate and data source delegate.
I also need to categorize the results into sections - these being
England
Scotland
Wales
N.Ireland
To get an idea of what JSON string I am using see this one.
As you can see the JSON does not cater for the sections but I am yet to implement this, so i would need to know beforehand so I do not have to amend much code later on.
OK - I am using Stig JSON parser.
Here is my ListVenuesView.h (connected to table view)
#import <UIKit/UIKit.h>
#import "SBJson.h"
#interface ListVenuesView : UITableViewController <UITableViewDelegate, UITableViewDataSource> {
IBOutlet UITableView *venueList;
NSMutableDictionary *jsonArray;
}
#property (nonatomic, retain) IBOutlet UITableView *venueList;
#property (nonatomic, retain) NSMutableDictionary *jsonArray;
#end
jsonArray is used to store the JSON data and eventually the proper array.
And here is my ListVenuesView.m (key areas in question)
- (void)viewDidLoad
{
[super viewDidLoad];
NSLog(#"Table View Loaded");
// Uncomment the following line to preserve selection between presentations.
// self.clearsSelectionOnViewWillAppear = NO;
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem;
// This is where we load the JSON data
NSURL *jsonURL = [NSURL URLWithString:#"http://www.thebigfishexperience.org.uk/sources/ajax/venue-json.php?location=peterborough"];
NSString *jsonData = [[NSString alloc] initWithContentsOfURL:jsonURL];
NSLog(#"%#", jsonData);
// Convert jsonData to array
self.jsonArray = [jsonData JSONValue];
NSLog(#"%#", jsonArray);
NSLog(#"count is: %i", [self.jsonArray count]);
// Release NSString and NSURL
[jsonURL release];
[jsonData release];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return [self.jsonArray count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
NSMutableDictionary *dict = [self.jsonArray objectAtIndex: indexPath.row];
cell.textLabel.font = [UIFont fontWithName:#"Arial" size:15.0];
cell.textLabel.text = [dict objectForKey:#"venueName"];
cell.detailTextLabel.text = [dict objectForKey:#"venueCordDist"];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
// Configure the cell...
return cell;
Also how can I use the data in the cells to go to another subview of the nav controller which gives me a back button and displays the info from the JSON string just for that particular cell that has been tapped.
I think this has something to do with it? Not sure though as this is my first app i am building! So probably expect more pleas of assistance - ha ! ;)
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// Navigation logic may go here. Create and push another view controller.
/*
DetailViewController *detailViewController = [[DetailViewController alloc] initWithNibName:#"Nib name" bundle:nil];
// ...
// Pass the selected object to the new view controller.
[self.navigationController pushViewController:detailViewController animated:YES];
[detailViewController release];
*/
}
On selecting a row, as mentioned by u, we are navigating to another view. Let us assume that the view controller is DetailViewController which is a sub-class of UIViewController.
In the DetailViewController.h , declare a NSDictionary object.
In DetailViewController.m, add
-(void)setVenueDict:(NSDictionary*)venueDict
{
if( _venueDict )
{
[_venueDict release];
}
_venueDict = [venueDict retain];
}
In ParentViewController, ur didSelectRow.. method should be like this.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// Navigation logic may go here. Create and push another view controller.
DetailViewController *detailViewController = [[DetailViewController alloc] initWithNibName:#"Nib name" bundle:nil];
// ...
// Pass the selected object to the new view controller.
NSDictionary *dict = [self.jsonArray objectAtIndex: indexPath.row];
[detailViewController setVenueDict:dict];
detailViewController.title = [dict objectForKey:#"venueName"];
[self.navigationController pushViewController:detailViewController animated:YES];
[detailViewController release];
}
In the second view controller, u can do whatever u want with the _venueDict.
Nathan,
since you want to reuse the data parsed from the JSON feed over more than one ViewController the best way to approach this is to build an object Model so that you can pass the object for the selected row in the list to the detail ViewController.
I would also separate the JSON parsing code into a separate class and not keep it in the ViewController.
You can find classes to fetch JSON on this link.
The result from the custom code to parse the JSON feed would give back a NSDictionary with as keys the section names you mention. And the value in the NSDictionary for those keys would be an array of your custom objects that contain all the relevant data for one row (and detail screen).
Hope this helps you on your way.
jsonArray is NSMutableDictionary.
have to use
[jsonArray objectForKey:key];
//check this line
NSMutableDictionary *dict = [self.jsonArray objectAtIndex: indexPath.row];
this may help.
have seen similar questions but couldn't find a definitive answer.
Having mastered regular tables of most types, I am doing some conceptual experiments with custom table cells to get familiar with how this works. I want to have a custom subclass of UITableViewCell which loads a nib to the contentView. I may want to implement different editing styles at some later point but want to reuse the custom view in different parts of my application, however, i'm having problem receiving the didSelectRowAtIndexPath message in my calling UITableViewController.
Here's the hierarchy which is built from a basic view template.
CustomCellViewController: A stock XCode objective-c class sublcassed from UITableViewCell
#interface CustomCellViewController : UITableViewCell {
IBOutlet UILabel *lbl;
}
#property (nonatomic, retain) IBOutlet UILabel *lbl;
#end
#implementation CustomCellViewController
#synthesize lbl;
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
// Initialization code
NSArray *a = [[NSBundle mainBundle] loadNibNamed:#"customCellView" owner:self options:nil];
UITableViewCell *tc = [a objectAtIndex:0];
NSLog(#"Cell loaded from nib");
[self.contentView addSubview:tc];
}
return self;
}
.. the other stock methods are unchanged ..
#end
I realise that the init method could be simplified but this is my first attempt.
The XIB file's owner is my custom class (CustomCellViewController), has a UITableViewCell and a label (linked to the outlet 'lbl' on it) positioned half way accross, leaving plenty of the underlying UITableViewCell clickable.
RootViewController is a standard, stock XCode subclass of UITableViewController
RootViewController sets up an instance variable "CustomTableCellController *myCustomCell"
The cellForRowAtIndexPath: is as follows:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"myCustomCell";
CustomCellViewController *cell = (CustomCellViewController *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[CustomCellViewController alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
NSLog(#"Creating New cell for position %d", indexPath.row);
} else {
NSLog(#"Reusing cell for position %d", indexPath.row);
}
// Configure the cell.
cell.lbl.text = [NSString stringWithFormat: #"Hi There %d", indexPath.row];
return cell;
}
And in the same RootViewController.m, my didSelectRowAtIndexPath:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSLog(#"Cell tapped at row %d", indexPath.row);
/*
<#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc] initWithNibName:#"<#Nib name#>" bundle:nil];
// ...
// Pass the selected object to the new view controller.
[self.navigationController pushViewController:detailViewController animated:YES];
[detailViewController release];
*/
}
Designed at present, to purely output a log message when tapped.
numberOfSectionsInTableView returns 1
numberOfRowsInSection returns 50
This all compiles and runs fine, iPhone simulator starts, I see a table on the display, my output log confirms it has created 9 versions of CustomCellViewController and I can see the reuse stack via the NSLog() comments.
I just can't select a row, doesn't matter where I click in the custom cell, nothing gets to my didSelectRowAtIndexPath: in my RootViewController which is where I expect it.
Is it that I have I not set a delegate somewhere and if so, how? Do I need to do this via a first responder? (ie, create a method in my CustomCellViewController class, link the UITableViewCell from the XIB to that method and then call [super didSelectRowAtIndexPath] - but how do I pass the indexPath?
Am I not responding to a message from my XIB in it's owner and then passing it on (is this how I do it?)
I read through all the apple docs to get to this stage but couldn't quite decipher how touch messaging happened.
Slightly confused!
May be you have forget to set data source and delegate if the tableview object set it as like below
tbl.delegate = self;
tbl.dataSource = self;
Just a quick question really:
I'm running a method to pull records from an sqlite database into an array, then assigning the contents of that array to an instance variable.
#interface {
NSArray *items;
}
#implementation
// The population method.
-(void)populateInstanceVariable
{
NSMutableArray *itemsFromDatabase = [[NSMutableArray alloc] init];
// Sqlite code here, instantiating a model class, assigning values to the instance variables, and adding this to the itemsFromDatabase Array.
self.items = itemsFromDatabase;
[itemsFromDatabase release];
}
// viewDidLoad is calling the method above
-(void)viewDidLoad
{
[self populateInstanceVariable];
[super viewDidLoad];
}
// TableViewDataSource method - cellforIndexPath
- (UITableViewCell *)tableView:(UITableView *)passedInTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault];
// Load in my model from the instance variable - ***1
MyDataModel *model = [items objectAtIndexPath:indexPath.row];
// Assign the title to the cell from the model data
cell.textLabel.text = model.title;
// This is the part i'm stuck on, releasing here causes a crash!
[model release];
return cell;
}
#end
My question is two fold:
Is what i'm doing to assign data to the instance variable right? and am i managing the memory correctly?
How do i manage the memory for that model item in the tableview datasource? the only way i seem to be able to get it to run smoothly is if i don't release the *model object at all, but that causes leaks surely?
Cheers.
No, you're not managing memory correctly here:
you should use "reusable" UITableViewCells, most UITableView examples show how to do this, and
do not do [model release], you do not "own" the object in this case, you're just referring to it so you must not release it
Here's the typical cellForRowAtIndexPath:
-(UITableViewCell *) tableView:(UITableView *)atableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"CellIdentifier";
// Dequeue or create a cell of the appropriate type.
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier] autorelease];
// settings that do not change with every row
cell.selectionStyle = UITableViewCellSelectionStyleGray;
}
// settings that change with every row
cell.textLabel.text = #"fill in your label here";
return cell;
}
Also, if you're using a DB for your data, you may want to look in to Core Data, Apple's data persistence/management framework, it includes the ability to hook aspects of your data entities directly up to UITableViews.
1) Populate method is correct. Don't forget to set the instance variable to nil in the dealloc. (I suppose you added a property/synthesize as you used the 'self.').
2) Do NOT release the model object. You did not retain, copy or allocated it in that method. By the other hand your initialization of the cell is wrong. Use the following: (Better for performance)
- (UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *Identifier = #"CellIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:Identifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:Identifier] autorelease];
}
//Other code
}