I am using a navigation based iPhone application, and I defined an IBOutlet propert in the inner view and synthesized it,
The issue is when I want to set the IBOutlet value before pushing the new view controller, the value won't be set. Here is a snippet from the code:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
MealDetailViewController *mealViewController = [[MealDetailViewController alloc] initWithNibName:#"MealDetailViewController" bundle:nil];
MealsModel *model = (MealsModel *)[_items objectAtIndex:indexPath.row];
NSLog(model.Name);// here it writes the name right as a string
//mealViewController.lblName.text=model.Name;
[[mealViewController lblName]setText:model.Name];
[[mealViewController txtDesc]setText:model.Description];
[self.navigationController pushViewController:mealViewController animated:YES];
[mealViewController release];
}
I didn't face like these issues in the previous versions of Xcode.
It's to do with when your view controller's views are being created.
When you do
[[mealViewController lblName] setText:model.Name];
you haven't loaded it's view yet so lblName will be nil.
Try either
(a) Explicitly asking for the view, triggering the subviews to be created :
[mealViewcontroller view];
[[mealViewController lblName]setText:model.Name];
[[mealViewController txtDesc]setText:model.Description];
or
(b) Letting the navigation controller create the views for you
[self.navigationController pushViewController:mealViewController animated:YES];
[[mealViewController lblName]setText:model.Name];
[[mealViewController txtDesc]setText:model.Description];
or
(c) Store the values in the mealViewController as properties
MealViewController.h
#property (nonatomic, copy) NSString *lblNameString;
#property (nonatomic, copy) NSString *txtDescString;
MealViewcontroller.m
#synthesize txtDescString, lblNameString;
and instead of setting the label directly, set the properties instead.
[mealViewController setLblNameString:model.Name];
[mealViewController setTxtDescString:model.Description];
Then, in your newWillAppear, setting them
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
lblName.text = lblNameString;
txtDesc.text = txtDescString;
}
(c) is the more correct way to do it - (a) and (b) both fail if your view controller's view is unloaded by a low memory warning.
What I would do is pass the *Meal object to the MealDetailViewController. Then use that to set the labels and such in the MealDetailViewController. Once I had a similar problem and found that I was initializing the property, a UILabel in ViewDidLoad of my receiving class so it was overwriting any passed in text.
Related
I have a view controller that has navigation bar with a done button, and two text fields. When the done button is pressed, the method postInfo is called. Here is the implementation:
- (void)postInfo{
ListingViewController* lvc = [[ListingViewController alloc] init];
NSString* listingName = listingNameField.text;
NSString* listingPrice = listingPriceField.text;
NSLog(#"%#", listingName);
NSLog(#"%#", listingPrice);
[lvc.titleLabel setText:listingName];
[lvc.priceLabel setText:listingPrice];
[self.navigationController pushViewController:lvc animated:YES];
}
Here ListingViewController.h:
#import <UIKit/UIKit.h>
#interface ListingViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *priceLabel;
#property (weak, nonatomic) IBOutlet UILabel *titleLabel;
#end
The UILabel's are set through a xib file and are empty. Will post whatever other code is needed upon request.
At the time you do that push, the next controller's view hasn't been loaded yet, so you can't access its views. You need to create NSString properties in ListingViewController and pass a string to those in your postnfo method. Then in ListingViewController's viewDidLoad method, use those properties to populate the labels (which will have been loaded by the time viewDidLoad runs).
Change your code to this.
- (void)postInfo
{
ListingViewController* lvc = [[ListingViewController alloc] init];
[lvc view]; // loads the view
NSString* listingName = listingNameField.text;
NSString* listingPrice = listingPriceField.text;
NSLog(#"%#", listingName);
NSLog(#"%#", listingPrice);
[lvc.titleLabel setText:listingName];
[lvc.priceLabel setText:listingPrice];
[self.navigationController pushViewController:lvc animated:YES];
}
This happens because until the view property of the view controller is accessed, the view will not be loaded and all of the subviews are nil. They can be configured after viewDidLoad is called on the view controller being pushed. Calling [lvc view] loads the view immediately.
I usually get this too (in the example of when using segues). I get around it by setting an NSString property instead of an IBOutlet during prepareForSegue of the destinationController. Then during viewDidLoad of the next View Controller, I take the value of the property and assign it to the UILabel.
You may find the explanation in this answer useful: https://stackoverflow.com/a/8094146/2358334
If you set a breakpoint just after the line you call
testViewController *viewController = segue.destinationViewController;
when you build and run the project, you will find that the UITextField
property in the destinationViewController is not allocated and
initiated (memory is 0x0) at the breakpoint. Meanwhile the NSString
property is already allocated and initialised (so you can set its
value).
Try to do this
first you need to load the view (push viewcontroller) and then you can access the properties (because you have created views by IBOutlet
- (void)postInfo{
ListingViewController* lvc = [[ListingViewController alloc] init];
NSString* listingName = listingNameField.text;
NSString* listingPrice = listingPriceField.text;
NSLog(#"%#", listingName);
NSLog(#"%#", listingPrice);
[self.navigationController pushViewController:lvc animated:YES];
[lvc.titleLabel setText:listingName];
[lvc.priceLabel setText:listingPrice];
}
My problem is that in ProductNote class UIButton Action I did initWithNibName Notes Class to show the popOver with a UITableView in Notes Class. I am fetching data from sqlite and then load it to UITableView in tableViewDidSelectRowAtindexPath:. I got the selectedNote and creates object of ProductNote Class to call selectedNote instance method that only set IBOutlet's textview.text but its nil. Thats my problem, Below is the code please help me to knowing why i face this type of issue. I am using Xcode 4.3.3 and not using ARC. Manually I defined dealloc method on every ViewController
//**ProductNote.h Class****************************
#import <UIKit/UIKit.h>
#class Notes;
#interface ProductNote : UIViewController<UIPopoverControllerDelegate>
{
UIPopoverController *popOverController;
UITextView *txtmesssagenotes;
Notes *objNotes;
}
#property (retain, nonatomic) IBOutlet UITextView *txtmesssagenotes; //It is Connected to ProductNote.xib
#property (retain,nonatomic) UIPopoverController *popOverController;
#property (retain,nonatomic) Notes *objNotes;
-(IBAction)presentPopOver:(UIButton*)sender;
-(void)selectedNote:(NSString*)note;
#end
//ProductNote.m Class
#implementation ProductNote
#synthesize txtmesssagenotes,popOverController,objNotes;
-(IBAction)presentPopOver:(UIButton*)sender
{
self.objNotes=[[Notes alloc]initWithNibName:#"Notes"bundle:nil];
UIPopoverController *popOver=[[[UIPopoverController alloc]initWithContentViewController:objNotes]autorelease];
self.popOverController=popOver;
self.popOverController.delegate=self;
self.popOverController.popoverContentSize=objNotes.view.frame.size;
CGRect rect=[self.view convertRect:objNotes.view.frame fromView:self.view];
rect.origin.y+=110;
rect.origin.x+=23;
[self.popOverController presentPopoverFromRect:rect inView:self.view permittedArrowDirections:0 animated:YES];
//Then I get popOver with tableview
}
-(void)selectedNote:(NSString*)note
{
self.txtmesssagenotes.text=note;
//Here I am getting txtmesssagenotes=0X0 or nil. Using self or without self Please tell me the reason.
}
- (void)dealloc {
[txtmesssagenotes release];
[popOverController release];
[objNotes release];
[super dealloc];
}
#end
#interface Notes : UITableViewController
{
NSMutableArray *arrNotes;
NSString *selectedNote;
UITableView *tblNotes;
}
#property(nonatomic,retain)NSMutableArray *arrNotes;
#property(nonatomic,retain)NSString *selectedNote;
#property(nonatomic,retain)IBOutlet UITableView *tblNotes;
#end
//Actually I skip the other methods that makes larger program to read . other methods only used to fetch data from sqlite and fill up the arrNotes that is used to fill all rows in the tableview.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
self.selectedNote=[self.arrNotes objectAtIndex:indexPath.row];
//Here self.arrNotes valid object and contains the data, and assigns NSString object to self.selectedNote
ProductNote *productNote=[[ProductNote alloc]init];
[productNote selectedNote:self.selectedNote]; //after calling selectedNote i goto to selectedNote implementation or definition above.
[productNote release];
}
-(void)dealloc
{
[arrNotes release];
[selectedNote release];
[tblNotes release];
[super dealloc];
}
It is because just as you stated that txtmesssagenotes was created using IB. And you never presented your ProductNote UIViewController instant productNote. So the txtmesssagenotes was never allocated and initialized properly.
Are you calling selectedNote: before your view has loaded?
Just because you created a view controller with a xib doesn't mean that it loads all your subviews immediately.
The xib is parsed and all your views are created the first time that the view controller's view property is asked for - this is usually just before it appears for the first time.
Until then, all the IBOutlet connections will be nil.
You need to store the text for your note as an NSString property of you view controller. Then, inside either viewDidLoad you need to call self.txtmesssagenotes.text=self.note; - viewDidLoad is automatically called just after your view is loaded so you are guaranteed to have all your IBOutlets set by then.
You shouldn't rely on your view objects to store the state of your app (in this case, the text of the note). If a low memory warning is received while your view controller isn't visible then all your view objects will be deleted - they will only be recreated when your view controller becomes visible again - if you are storing your note string inside a UITextView then it might no be there the next time you ask for it :) You should always store data in a property of your view controller (or somewhere else you control) and create your views using it.
im new to IOS and Objective-C and the whole MVC paradigm and i'm stuck with the following.
I am working on (replica) Contact app, also available in iphone as build in app. i want to pass data through another view controller and the data is pass (null) :(.
My Question is, How do I transfer the data from one view to another?
As most the answers you got, passing data between one controller and another just means to assign a variable from one controller to the other one.
If you have one controller to list your contacts and another one to show a contact details and the flow is starting from the list and going to detail after selecting a contact, you may assign the contact variable (may be an object from the array that is displayed in your list) and assign it to the detail view controller just before showing this one.
- (void)goToDetailViewControllerForContact:(Contact *)c
{
ContactDetailViewController *detailVC = [[[ContactDetailViewController alloc] init] autorelease];
detailVC.contact = c;
[self.navigationController pushViewController:c animated:YES];
//[self presentModalViewController:detailVC animated:YES]; //in case you don't have a navigation controller
}
On the other hand, if you want to insert a new contact from the detail controller to the list controller, I guess the best approach would be to assign the list controller as a delegate to the detail one, so when a contact is added the delegate is notified and act as expected (insert the contact to the array and reload the table view?).
#protocol ContactDelegate <NSObject>
- (void)contactWasCreated:(Contact *)c;
// - (void)contactWasDeleted:(Contact *)c; //may be useful too...
#end
#interface ContactListViewController : UIViewController <ContactDelegate>
#property (nonatomic, retain) NSArray *contacts;
...
#end
#implementation ContactListViewController
#synthesize contacts;
...
- (void)goToDetailViewControllerForContact:(Contact *)c
{
ContactDetailViewController *detailVC = [[[ContactDetailViewController alloc] init] autorelease];
detailVC.contact = c;
detailVC.delegate = self;
[self.navigationController pushViewController:c animated:YES];
//[self presentModalViewController:detailVC animated:YES]; //in case you don't have a navigation controller
}
- (void)contactWasCreated:(Contact *)c
{
self.contacts = [self.contacts arrayByAddingObject:c]; //I'm not sure this is the correct method signature...
[self reloadContacts]; //may be [self.tableView reloadData];
}
...
#end
#interface ContactDetailViewController : UIViewController
#property (nonatomic, assign) id<ContactDelegate> delegate;
...
#end
#implementation ContactDetailViewController
#synthesize delegate; //remember to don't release it on dealloc as it is an assigned property
...
- (void)createContactAction
{
Contact *c = [[[Contact alloc] init] autorelease];
[c configure];
[self.delegate contactWasCreated:c];
}
...
#end
Technically, you shouldn't!
The whole idea is not for "views" to control what happens to the data.
What you want to do is to pass data between controllers (which I imagine is exactly what you are planning to do anyway).
You can have shared model (an instance of an object that both view controllers would access) keeping the data you want to share,
You can use notifications to pass data (it is best suited for certain cases).
You can write something to disk and read it again later.
You can use NSUserDefaults.
You can use KeyChain.
...
The best way is:
declare the appropriate #property in the second view controller
when you create it, simply set the property with
viewController.property = valueYouWantToPass;
I'm a big fan of delegates and protocols.
And in some occasions use a Singleton pattern.
two ways to pass/share data between view controller
create an object and sent the data like this
QGraduteYr *tableverify=[[QGraduteYr alloc]initWithStyle:UITableViewStyleGrouped];
tableverify.mystring=myString
[self.navigationController pushViewController:tableverify animated:YES];
another method is stor it in the delegates and use it via shared delegates
MedicalAppDelegate *appdelegate=(MedicalAppDelegate *)[[UIApplication sharedApplication]delegate];
appdelegate.collnameStr=collStr;
and ust this appdelegates value whereever you need
I am building a utility-based application, the data is stored in the MainViewController, and now I know how to pass data to the FlipsideViewController (many regards to this thread BTW, Sending data from Mainview to Flipside?). But I am getting the data onto an subview (subclass of UIView) that I have added to the flipside view. How can I pass data to this subview? I saw there is already a delegate and protocol set up in the FlipsideViewController.h, I am really new to the delegate sort of things. Any help would be greatly appreciated!
Updates:
On the main view, I have a couple of text fields for users to input to create an object. All the objects are stored in an array. Namely, my data is created and stored in the MainViewController. Now on the flip side, I have a custom UIView subclass which allows me to do my own drawing based on the data in that array. What I need to do here is pass the data that stored in MainViewController to this subview. Here is my relevant code:
In the MainViewController.m
- (IBAction)showInfo:(id)sender {
FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:#"FlipsideView" bundle:nil];
controller.delegate = self;
controller.receiver = data;//this is what I've done.
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
[controller release];
}
In the FlipsideViewController.h
#protocol FlipsideViewControllerDelegate;
#interface FlipsideViewController : UIViewController {
id <FlipsideViewControllerDelegate> delegate;
DataModel *receiver; //create a property to receive the data transferred from main view
}
#property (nonatomic, assign) id <FlipsideViewControllerDelegate> delegate;
#property (nonatomic, retain) DataModel *receiver;
- (IBAction)done:(id)sender;
#end
#protocol FlipsideViewControllerDelegate
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;
#end
In the above code, "data" is an DataModel object declared in the MainViewController.h file.
And I want to do my custom drawing in drawing class (subclass of UIView), how can I pass data from the FlipsideViewControllerto this subview? Do I need to make use of delegate declared in the FlipsideViewController.h file? Thanks in advance!
I have had a quick look at the template and think you are getting confused with what the delegate is being used for.
The delegate in this template is not transferring data. When you have clicked the done button it calls back to MainViewController and asks it to call the dismissModalViewControllerAnimated method so that it can remove the view controller. This seems a bit superflous as the documentation states
If you call this method on the modal view controller itself, however, the modal view controller automatically forwards the message to its parent view controller.
Therefore you don't really need to call the parent to do this.
In Interface builder you can see that the FlipsideView.xib has it's File's Owner set to FlipsideViewController.xib.
Now if you right click the File's Owner you will see that view is connected to View this basically means that view is the name of the property in FlipsideViewController and View is the element in Interface Builder.
Therefore we can access elements in the xib file from FlipsideViewController using outlets.
To say draw a label you will need to do a couple of things
First add a property in the .h and synthesize it in the .m like
// FlipsideViewController.h
#interface FlipsideViewController : UIViewController
#property (nonatomic, retain) IBOutlet UILabel *testLabel; // <----- Added this
#property (nonatomic, assign) id <FlipsideViewControllerDelegate> delegate;
- (IBAction)done:(id)sender;
#end
// FlipsideViewController.m
#implementation FlipsideViewController
#synthesize delegate = _delegate;
#synthesize testLabel = _testLabel; // <----- Added this
// More methods
- (void)dealloc
{
[_testLabel release]; // Always do you memory management
[super dealloc];
}
Then back in Interface Builder
Add a UILabel element to your view
ctrl + drag from File's Owner to the UILabel you added
Select the label in my example it is testLabel
Now these are hooked up correctly. The place where you want to be setting the value of the label is in viewDidLoad: which you can now do like this
- (void)viewDidLoad
{
[super viewDidLoad];
self.testLabel.text = #"It Works"; // You would use the data passed in from `MainViewController`
}
I find the easiest way to pass data from one view to another is by directly setting the data in the next view from the original view.
For example;
In your FlipsideViewController.h, declare a 'container' for the data you want to pass. It must be the same class on both sides to work properly, ie. NSArray to NSArray, NSMutableDictionary to NSMutableDictionary.
NSMutableArray *newData;
...
#property (nonatomic, retain) NSMutableArray *newData; // This allows you to access this object from outside this class.
and in FlipsideViewController.m
#synthesize newData;
...
[newData release];
Now we need to pass the data, so to speak. Let's say the data we want to 'send' is stored in a NSMutableArray called 'results'.
In our MainViewController.m, when we are instantiating our next view controller (in this case FlipsideViewController) we can directly reference the newData mutable array after we initalize the nib.
FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:#"FlipsideView" bundle:nil];
controller.newData = results;
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
[controller release];
Make sure you are importing your FlipsideViewController in your MainViewController.h file.
If the property is declared in your .h file, you can pretty much reference the contents of the object from anywhere within the view stack!
Hope that helps :D
I have 2 view controllers now, And it both got tableviews.
When I choose a row in the second tableview (Using didSelectRowAtIndexPath),
and I want to pass the Information I got in the second View to the first View,
I tried to use delegate&protocol, but don't know why, It didn't work.
And I tried to use class method inside the first class, when I got variable in sencond View,
Call the class method inside the first class. The variable successfully pass to first View,
but when I want to set the Lable's text, it still failed..
Can somebody teach me how to do? thanks!
My protocol&delegate.
This is the second view.
#protocol CategoriesViewControllerDelegate;
#interface CategoriesViewController : UIViewController {
TableViewNewAppDelegate *appDelegate;
id <CategoriesViewControllerDelegate> delegate;
}
#property (nonatomic, assign) id <CategoriesViewControllerDelegate> delegate;
#end
#protocol CategoriesViewControllerDelegate <NSObject>
-(void)backstring:(NSString *)String;
#end
In the .m file , synthesize it
#implementation CategoriesViewController
#synthesize delegate;
didSelectRowAtindexPath
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
CategoryData *CateObj = [appDelegate.CateArray objectAtIndex:indexPath.row];
NSString *Strings = [NSString stringWithString:CateObj.CateTitle];
[delegate backstring:Strings];
[self.parentViewController dismissModalViewControllerAnimated:YES];
}
In the first view controller .h file.
#import "CategoriesViewController.h"
#interface DataController : UIViewController <CategoriesViewControllerDelegate>{
.m file
-(void)backstring:(NSString *)String {
NSLog(#"%#",String);
jCateField.text = String;
}
This is how I do my protocol+delegate. Are there something wrong?
btw, I created a Class method in the first view controller, and use the Class method in the sencond view controller, it succesfully pass variable to first view controller.
But the problem is, I can't set my Label's text inside my Class method, even calling Instance method to set text. Is there any way to solve this problem?
The code you provided seems to be correct. In your case you must set :
#property (nonatomic, assign) id <CategoriesViewControllerDelegate> delegate;
correctly to point to the first view controller which conforms to the protocol you defined :
#import "CategoriesViewController.h"
#interface DataController : UIViewController <CategoriesViewControllerDelegate>{
So it seems that you pushed a CategoriesViewController onto a first DataController, you probably missed to do so just before.
// self is the first view controller
// [myCategoriesViewController setDelegate:self]; old fashion
myCategoriesViewController.delegate = self;
[self presentModalViewController:myCategoriesViewController animated:YES];
This can probably solve your issue. Hope this helps.
Also consider let the first controller dismiss the second.
Here is a link to Apple's documentation.
You could just pass the information straight on to your second view controller;
SecondViewController.h
#interface SecondViewController
{
Information *info;
}
#property (nonatomic, retain) Information *info;
#end
SecondViewController.m
#implementation SecondViewController
#synthesize info;
...
#end
And in your didSelectRowAtIndexPath method;
SecondViewController *controller = [[SecondViewController alloc] initWithNibNamed:#"SecondViewController" bundle:nil];
[controller setInfo:YOUR_INFO_OBJECT];
[self.navigationController pushViewController:controller animated:YES];
[controller release];
Import second view controller header file in the first view controller implementation file. Import first view controller header file in second view controller header file.
Create the property (text/label/whatever) in the first view controller.
Create the property of first view controller in the second view controller.
Create the second view controller instance, set the first view controller property to what you need, push controller to the navigation controller. In the second view controller change whatever you want in the first view controller. Instance methods allowed. Do not forget to release first view controller.
Delegate pattern works in that way too.
View controllers are objects. Objects can have methods that can be called from other objects, and they can have instance variables. ("Delegate" is just a fancy term for this.)
There's no inherent reason why passing data between your view controllers should be hard or complicated, so long as the caller has the address of the callee. (And whether or not a given VC has an XIB is irrelevant.)
It sounds like your real problem is not knowing what to do with the data once it's been passed to the callee.
Stupid question: Is "jCateField" actually connected to the label you want to change, or is it nil? If you created the label from code (since you don't have an XIB), you will need to have stored the created label's address into "jCateField" during the view creation.
Can you post the code for as to ho you are displaying the contents when you come back to 1 st view controller.As here if the log gives you proper value then the issue is with the connection (if taken through iboutlet) or with addsubview .
Do you get nil in label or no value (label is hidden).