I have 4 buttons on main screen, each one sends me to a viewController. The third one, sends me to a view on which I wanna set the managedObjectContext. If I use the class name to create an instance, it's all right. But I'm looking for a way to use just one method that uses an array to retrieve the name of the Class for the needed viewController. But it's leading to an error message, like it doesn't exist on the destination viewController??? Anyone have any ideas about this aproach??? Thanks in advance!
Here is the code:
NSArray *viewControllers = [[NSArray alloc]
initWithObjects:#"nil",#"OpcoesView",#"nil",#"TheNames", nil];
NSString *viewName = [viewControllers objectAtIndex:[sender tag]]; //the taped button tag
UIViewController *viewController = [[NSClassFromString(viewName) alloc]
initWithNibName:viewName bundle:nil];
if ([sender tag] == 3) {
viewController.managedObjectContext = contexto;
}
You do not need to know the subclass at all. Because Objective-C is a dynamic language and messages are resolved at runtime, you can send the message without having to know anything about the subclass at all.
First I would refer to the subclass as an id (instead of UIViewController) and as long as you have its header imported you can call [viewController setManagedObjectContext:contexto] directly.
However if you don't want to or can't import the header then just use KVC as follows:
[viewController setValue:contexto forKey:#"managedObjectContext"];
I would keep MOC in my app delegate instead of assigning it down to every of my viewControllers:
And in my viewController .m file:
#import "MyAppDelegate.h" // Assuming you have a property called managedObjectContext in your MyAppDelegate
#interface MyViewController (PrivateMethgods)
#property (nonatomic, readonly) NSManagedObjectContext * managedObjectContext;
#end
#implementation MyViewController
#dynamic managedObjectContext
- (NSManagedObjectContext *)managedObjectContext {
MyAppDelegate *appDelegate = (MyAppDelegate *)[UIApplication sharedApplication].delegate;
return appDelegate.managedObjectContext;
}
So I can use it in my viewController like this:
if ([self.managedObjectContext hasChanges]) {
...
}
To set a property that is only in the subclass view controller (such as "managedObjectContext"), you can take advantage of the fact that you know the type like this:
NSArray *viewControllerNames = [[NSArray alloc] initWithObjects:#"nil",#"OpcoesView",#"nil",#"TheNames", nil];
NSString *viewControllerName = [viewControllerNames objectAtIndex:[sender tag]]; //the tapped button tag
UIViewController *viewController = [[NSClassFromString(viewControllerName) alloc] initWithNibName:viewControllerName bundle:nil];
if ([sender tag] == 3) {
TheNames *namesVC = (TheNames*)viewController;
namesVC.managedObjectContext = contexto;
}
Related
This question already has answers here:
What's the best way to communicate between view controllers?
(4 answers)
Closed 9 years ago.
I have NSObject class that has a NSString called tweetTitle;
TweetDesc.h file
#import <Foundation/Foundation.h>
#interface TweetDesc : NSObject
#property (strong, nonatomic) NSString * tweetTitle;
-(void) setFullTweetTitle:(NSString *) fullTweetTitle;
#end
TweetDesc.m file
#implementation TweetDesc
#synthesize tweetTitle;
-(void) setFullTweetTitle:(NSString *) fullTweetTitle
{
self.tweetTitle = fullTweetTitle;
}
#end
I have three classes (View Controllers), FirstViewController, SecondViewController and ThirdViewController.
Here are the code of FirstViewController
FirstViewController.h
#interface TweetViewController : UIViewController <UITextViewDelegate>
#property (strong, nonatomic) NSString * tweet;
#property (weak, nonatomic) IBOutlet UITextView *tvTweetTitle;
- (IBAction)btnCreateTweet:(id)sender;
#end
FirstViewController.m
#implementation TweetViewController
#synthesize tvTweetTitle, tweet;
- (void)viewDidLoad
{
[super viewDidLoad];
self.tvTweetTitle.delegate = self;
}
- (IBAction)btnCreateTweet:(id)sender
{
tweet = [[NSString alloc]initWithFormat:#"%#", tvTweetTitle.text];
TweetDesc * td = [[TweetDesc alloc]init];
[td setFullTweetTitle:tweet];
SecondViewController * svc = [self.storyboard instantiateViewControllerWithIdentifier:#"SecondViewController"];
[self.navigationController pushViewController:ivc animated:YES];
}
My Question is: How can I use tweetTitle in Second and third ViewController without creating new instance of TweetDesc class and set again the tweetTitle in every ViewControler.
In the second view controller I tried:
TweetDesc * td = [[TweetDesc alloc]init];
NSLog(#"%#", td.tweetTitle);
but I get null, it seems that it was released already or something else.
Thanks for the help in advance.
Just give SecondViewController a TweetDesc property, like this:
#interface TweetDesc : UIViewController
#property (nonatomic, strong) TweetDesc *tweetDesc;
...
Then, after you instantiate a SecondViewController, set its tweetDesc property:
SecondViewController * svc = [self.storyboard instantiateViewControllerWithIdentifier:#"SecondViewController"];
svc.tweetDesc = td;
[self.navigationController pushViewController:svc animated:YES];
In your SecondViewController implementation, use self.tweetDesc to access the instance.
First thing you don't need a class for a single property use the string only. There are several ways of doing this.
First you can have a tweet property globally defined in AppDelegate.
You can pass the variable reference from one to another viewcontrolleres.
Or, you can use NSUserDefaults to set and get the text.
In your case first one is more useful. Just do as follows
In AppDelegate.h
Define a property as NSString *tweetText;
Now in you action
- (IBAction)btnCreateTweet:(id)sender
{
AppDelegate *appDelegate=(AppDelegate *)[[UIApplication sharedApplication] delegate];
appDelegate.tweetText=tvTweetTitle.text;
}
Then in any controller you want to access the value just use
AppDelegate *appDelegate=(AppDelegate *)[[UIApplication sharedApplication] delegate];
NSLog("%#",appDelegate.tweetText);
Same approach can be used for NSUserDefaults as to set value
[[NSUserDefaults standardUserDefaults] setObject:tvTweetTitle.text forKey:#"Tweet"];
[[NSUserDefaults standardUserDefaults] synchronize];
and to get
NSLog("%#",[[NSUserDefaults standardUserDefaults] valueForKey:#"Tweet"]);
Make sure you set the values before navigating to other controllers..
The above should solve your purpose..
Based on your comment I feel you want each of your view controllers to hold a TweetDesc object. For that you could have a base class like
#interface baseViewController:UIViewController
#property(strong, nonatomic)TweetDesc *td;
#end
All your viewcontrollers should derive from this base class. So that your controllers definition look like this -
#interface FirstViewController:baseViewController
...
#end
#interface SecondViewController:baseViewController
...
#end
#interface ThirdViewController:baseViewController
...
#end
U instantiate it in the FirstViewController -
TweetDesc * td = [[TweetDesc alloc]init];
[td setFullTweetTitle:#"whatever string you want"];
And pass it on to SecondViewController - //like in Rob Mayoff's answer
SecondViewController * svc = [self.storyboard instantiateViewControllerWithIdentifier:#"SecondViewController"];
svc.tweetDesc = td;
[self.navigationController pushViewController:svc animated:YES];
INSIDE SecondViewController you may refer it as self.tweetDesc. And pass it on to whichever viewcontroller you want after this using the above code.
ThirdViewController *third= [self.storyboard instantiateViewControllerWithIdentifier:#"ThirdViewController "];
third.tweetDesc = self.tweetDesc;
[self.navigationController pushViewController:third animated:YES];
Pass it on the ANY viewcontroller just make sure it's base class is the baseClassViewController.
You need to use category of TweetDesc where you create method that adds your default title. Or you can create singleton of TweetDesc that will always hold one title.
In your ViewController create a method called initWithTweetDesc. The method will look like this:
- (id)initWithTweetDesc:(TweetDesc*)tweet
{
self = [super init];
if (self) {
_tweet = tweet;
}
return self;
}
Now, when you want to move to the new view controller, run this code:
TweetViewController *vc = [[TweetViewController alloc] initWithTweetDesc:tweetDesc];
[self.navigationController pushViewController:vc animated:YES];
You can use your AppDelegate for this.
eclare the property #property(nonatomic, strong) TweetDesc * td; in AppDelegate.h file.
And change the method like:
- (IBAction)btnCreateTweet:(id)sender
{
tweet = [[NSString alloc]initWithFormat:#"%#", tvTweetTitle.text];
TweetDesc * td = [[TweetDesc alloc]init];
[td setFullTweetTitle:tweet];
[[[UIApplication sharedApplication] delegate] setTd:td];
SecondViewController * svc = [self.storyboard instantiateViewControllerWithIdentifier:#"SecondViewController"];
[self.navigationController pushViewController:ivc animated:YES];
}
And in your second and third view controllers you can get the value using:
TweetDesc *desc = [[[UIApplication sharedApplication] delegate] td];
NSLog(#"%#",desc.fullTweetTitle);
I have a TableViewController that segues into a TabBarViewController.
I know how to pass my object via a segue, but not by a relationship like the TabBarViewController and it's tab share.
How can I do this? From the TabView is there a way to access the TabBarViewControllers member variables?
Update:
This is how I've solved the problem so far, but I'm not crazy about using the AppDelegate to do this...
Add the Following to WhateverYouNamedYourAppDelegate.h
#class myObjectIWantToPass;
#property (strong, nonatomic) myObjectIWantToPass *object;
Then add the following to the View Class file you have your data in that you want to pass on. I'm going to assume you know how to set up your object already in this file if your planning on passing it to another view.
WhateverYouNamedYourAppDelegate *appDelegate =
(WhateverYouNamedYourAppDelegate *)[[UIApplication sharedApplication] delegate];
appDelegate.object = object;
Then you do some similar work to retrieve the object back from the appDelegate in your destination View Class.
WhateverYouNamedYourAppDelegate *appDelegate = (WhateverYouNamedYourAppDelegate *)[[UIApplication sharedApplication] delegate];
object = appDelegate.object;
You can make singleton classes, so that all of the controllers can access those variables in the Singleton. See Code below
SingletonClass.h
#interface SingletonClass : NSObject {
NSString *someString;
}
#property(nonatomic, retain)NSString *someString;
+(id)shared;
#end
SingletonClass.m
#import "SingletonClass.h"
static SingletonClass *aShared;
#implementation LibShared
#synthesize someString;
+(id)shared
{
if (aShared == nil) {
aShared = [[self alloc] init];
}
return aShared;
}
-(id)init
{
if (self = [super init]) {
}
}
-(void)dealloc
{
[someString releease];
[super dealloc];
}
In the tabbar you can set the variable on SingletonClass:
[[SingletonClass shared] setSomeString:#"Value_Set"];
On the tableViewController, you can get the property of the someString variable on the SingletonClass:
NSString *string = [[SingletonClass shared] someString];
There's no need for a singleton pattern here. Instead, you can send the data-object forwards in - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender just as you do normally, you just need to find the correct viewController in the UITabBarController's viewControllers property.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"MyTabBarSegue]) {
UITabBarController *tabBarController = segue.destinationViewController;
// Either set the index here, if you know for sure which viewController is which, or
// Enumerate the viewControllers for isKindOfClass:[MYCustomViewController class] to be robust and change-proof
MYCustomViewController *myVC = [[tabBarController viewControllers] objectAtIndex:0];
myVC.dataObject = self.dataObject;
}
}
In my Application,
There are two different views ItemList And ItemSearch.
In ItemList file I have one NsMutableArray with name tblItem. I want pass data in tblitem from the Itemsearch page.
How can I do this?
You can make use of properties as follows:
1.Create a property in ItemList.h of tblItem as,
#property(nonatomic, retain) NSMutableArray *tblItem;
then synthesize it in ItemList.m,
#synthesize tblItem;
When you are navigating from ItemSearch to ItemList ie when you are initializing ItemList just provide tblItem the required values as,
ItemListObj.tblItem = theSearchedArray;
Declare an NSMutableArray as property in the SecondViewController and assign the array at the time you are pushing or presenting the SecondViewController from the FirstViewController.
#interface SecondViewController : UIViewController
{
NSMutableArray *aryFromFirstViewController;
}
#property (nonatomic,retain) NSMutableArray *aryFromFirstViewController;
#end
At the implementation, synthesize the property
#implementation SecondViewController
#synthesize aryFromFirstViewController;
#end
At the header of the FirstViewController import the SecondViewController
#import "SecondViewController.h"
At implementation of the FirstViewController, add the code like below in where you wrote the code to present or push the SecondViewController
#implementation FirstViewController
- (void) functionForPushingTheSecondViewController
{
SecondViewController *objSecondViewController = [[SecondViewController alloc] initWithNIBName: #"SecondViewController" bundle: nil];
objSecondViewController.aryFromFirstViewController = self.myAryToPass;
[self.navigationController pushViewController:objSecondViewController animated: YES];
[objSecondViewController release];
}
#end
Please don't forget to release the aryFromFirstViewController at dealloc method of SecondViewController, otherwise it will leak because we retained it. I'l feel good if i come to know that this helped you in someways. Enjoy.
It depends on your need. You can use Singleton class for sharing of your variables between different classes. Define all variable which you wants share in your DataClass.
in .h file (where RootViewController is my DataClass, replace name with your new class)
+(RootViewController*)sharedFirstViewController;
in .m file
//make the class singleton:-
+(RootViewController*)sharedFirstViewController
{
#synchronized([RootViewController class])
{
if (!_sharedFirstViewController)
[[self alloc] init];
return _sharedFirstViewController;
}
return nil;
}
+(id)alloc
{
#synchronized([RootViewController class])
{
NSAssert(_sharedFirstViewController == nil,
#"Attempted to allocate a second instance of a singleton.");
_sharedFirstViewController = [super alloc];
return _sharedFirstViewController;
}
return nil;
}
-(id)init {
self = [super init];
if (self != nil) {
// initialize stuff here
}
return self;
}
after that you can use your variable in any other class like this
[RootViewController sharedFirstViewController].variable
Hope it's help you:)
I have a view with a view controller and when I show this view on screen, I want to be able to pass variables to it from the calling class, so that I can set the values of labels etc.
First, I just tried creating a property for one of the labels, and calling that from the calling class. For example:
SetTeamsViewController *vc = [[SetTeamsViewController alloc] init];
vc.myLabel.text = self.teamCount;
[self presentModalViewController:vc animated:YES];
[vc release];
However, this didn't work. So I tried creating a convenience initializer.
SetTeamsViewController *vc = [[SetTeamsViewController alloc] initWithTeamCount:self.teamCount];
And then in the SetTeamsViewController I had
- (id)initWithTeamCount:(int)teamCount {
self = [super initWithNibName:nil bundle:nil];
if (self) {
// Custom initialization
self.teamCountLabel.text = [NSString stringWithFormat:#"%d",teamCount];
}
return self;
}
However, this didn't work either. It's just loading whatever value I've given the label in the nib file. I've littered the code with NSLog()s and it is passing the correct variable values around, it's just not setting the label.
Any help would be greatly appreciated.
EDIT: I've just tried setting an instance variable in my designated initializer, and then setting the label in viewDidLoad and that works! Is this the best way to do this?
Also, when dismissing this modal view controller, I update the text of a button in the view of the calling ViewController too. However, if I press this button again (to show the modal view again) whilst the other view is animating on screen, the button temporarily has it's original value again (from the nib). Does anyone know why this is?
When a view controller is being initialized, inside the initWithNibName method, the views that reside in the view controller aren't yet initialized and you can't set their properties yet. Do whatever you need that is view based in the "viewDidLoad" method.
I am not a pro but this may help you.
In the header view1.h, declare the desired property:
// view1.h
#interface view1 : UIViewController {
NSString *passingVariable;
}
#property (nonatomic, strong) NSString *passingVariable;
#end
and then in the implementation of view1, synthesize the variable:
// view1.m
#implementation view1
#synthesize passingVariable;
// the rest of the implementation
#end
and, finally in the implementation of the other view controller, view2:
// view2.m
#import "view1.h"
#implementation view2
-(IBAction)changeview
{
view1 *myview = [[view1 alloc] init];
myview.passingVariable = #"Hello Variable";
[self.navigationController pushViewController:myview animated:YES];
}
#end
here i am trying to move from view2 to view 1 and also initializing the passingVariable ivar of view1. hope this will help you.
Here i'm passing the ViewController's label text to SecondViewController's Label Text
ViewController.h
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
{
// please make your control on XIB set these IBOutlet's
//I'm not showing how to connect these with XIB
IBOutlet UILabel *lblView;
IBOutlet UIButton *buttonGo;
}
//this is method which will push the view
-(IBAction)buttonGoClickAction:(id)sender;
ViewController.m
-(IBAction)buttonGoClickAction:(id)sender
{
SecondViewController *secondViewObject = [[SecondViewController alloc]initWithNibName:#"SecondViewController" bundle:nil];
//before pushing give the text
secondViewObject.string = lblView.text;
[self.navigationController pushViewController:secondViewObject animated:YES];
}
SecondViewController.h
#import <UIKit/UIKit.h>
#interface SecondViewController : UIViewController
{
IBOutlet UILabel *labelView;
NSString *string;
}
//set the string property
#property(nonatomic, retain) NSString *string;
#end
SecondViewController.m
#import "SecondViewController.h"
#implementation SecondViewController
//synthesize string here
#synthesize string;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
//Here you will get the string
labelView.text = string;
}
Firstly you check that have you attach this label IBOutlet in xib or not if you made it via Interface Builder....
use it like this....
SetTeamsViewController *vc = [[SetTeamsViewController alloc] initWithTeamCount:teamCount];
Take a string variable in .h file and set that string here .. NSSting *str in .h
- (id)initWithTeamCount:(int)teamCount {
self = [super init];
if (self) {
// Custom initialization
str = [NSString stringWithFormat:#"%d",teamCount];
}
return self;
}
and set your label in viewDidLoad: or in viewWillApear:
self.teamCountLabel.text = str;
May this will help you
As said by stavash, control in the xib are created in the view did load. To be more precise, they are created with that line :
[super viewDidLoad];
So, mylabel doesn't exist before that time (it is nil).
The easiest way is to do that :
SetTeamsViewController *vc = [[SetTeamsViewController alloc] init];
[self presentModalViewController:vc animated:YES];
vc.myLabel.text = self.teamCount;
[vc release];
The longer but more correct path is to have a member NSString* in SetTeamsViewController class, to set it to teamCount before showing the window, and in the view did load to put that membre value in your label.
Cdt
It depends on your need. You can use Singleton class for sharing of your variables between different classes. Define all variable which you wants share in your DataClass.
in .h file (where RootViewController is my DataClass, replace name with your new class)
+(RootViewController*)sharedFirstViewController;
in .m file
//make the class singleton:-
+(RootViewController*)sharedFirstViewController
{
#synchronized([RootViewController class])
{
if (!_sharedFirstViewController)
[[self alloc] init];
return _sharedFirstViewController;
}
return nil;
}
+(id)alloc
{
#synchronized([RootViewController class])
{
NSAssert(_sharedFirstViewController == nil,
#"Attempted to allocate a second instance of a singleton.");
_sharedFirstViewController = [super alloc];
return _sharedFirstViewController;
}
return nil;
}
-(id)init {
self = [super init];
if (self != nil) {
// initialize stuff here
}
return self;
}
after that you can use your variable in any other class like this
[RootViewController sharedFirstViewController].variable
Hope it's help you:)
With Storyboards the the right way is to pass the indexPath as sender argument in performSegueWithIdentifier
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
[self performSegueWithIdentifier:#"segueIdentifier" sender:indexPath];
}
and to set a property in the destination controller:
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString: #"segueIdentifier"]) {
NSIndexPath *indexPath = sender;
DetailViewController *dest = [segue destinationViewController];
dest.usersArray = [self.usersArray objectAtIndex:indexPath.row];
}
}
What I have done whenever I needed another class to have the variables from the previous class I either set up a global class that will store the values incase I need them in more locations or in the interface you can set #public variables. These variables can be set using the controller that you created for the next view as such.
controller->pub_var1 = val1;
controller->pub_var2 = val2;
This will be done before you pass the view to the root controller or just before you call the next view. You will need to #import "class.h" so that you can access those public variables.
I can show code if this is not clear
FirstViewController.h:
#import <UIKit/UIKit.h>
#interface FirstViewController : UIViewController
{
NSArray *listData;
}
-(IBAction) GoToInsert: (id) sender;
#property (nonatomic, retain) NSArray *listData;
#end
FirstViewController.m:
-(IBAction) upisiRezultat:(id)sender
{
SecondViewController *secondView = [[SecondViewController alloc] initWithNibName: nil bundle: nil];
[self presentModalViewController: secondView animated: NO];
[secondView release];
}
- (void)viewDidLoad
{NSArray *array = [[NSArray alloc] initWithObjects:#"236", #"46",
#"147", #"8", #"56", #"69", #"114", #"2",
#"96", #"518", #"2", #"54", #"236", nil];
self.listData = array;
[array release];
[super viewDidLoad];
}
SecondViewontroller.h
#interface SecondViewController : UIViewController {
}
-(IBAction) insert;
#end
SecondViewontroller.m
-(IBAction) insert
{
/* Here should be the code to insert some number in listData from FirstViewController */
}
So when the app loads it loads FirstViewController.xib and shows the listData array on screen, when I click button "Go to Insert" another view is loaded (SecondViewController.xib) with button "Insert" which should add some number into the array and display the new array on the first view.
How to do that?
You can access the parent view controller with self.parentViewController. Therefore something along these lines (meaning I haven't tested this -- you should) should work:
FirstViewController *firstViewController = self.parentViewController;
NSMutableArray *newArray = [[NSMutableArray alloc] initWithArray:firstViewControl.listData];
[newArray addObject:#"42"];
[firstViewController setListData:[NSArray arrayWithArray:newArray]];
[newArray release];
However, since you want to add objects to listArray, it would be more natural to use an NSMutableArray instead. Also, you are currently adding NSStrings to the array, when it looks more like you want to have NSNumber objects.
Alternately, and maybe easier, you could have the variables in your main AppDelegate.
Put:
int myNumber;
in the projectname_AppDelegate.h file
Then in each of your view controllers, you can import your AppDelegate.h file and then do something like:
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
and then read or change:
appDelegate.myNumber
===
This is not something you should be doing all the time (you don't want your appDelegate to be a giant data repository) but it could give you a quick fix when needed...
I do not know if you have imported the SecondViewController.h , and I think I have an idea an what you are trying to do.