I'm trying to set a variable in another view.
I'm in a view which I have named ProgramViewController and from here I would like to set a variable named bands in MyViewController.
I thought it would be as simple as
MyViewController *myViewController = [[MyViewController alloc] init];
myViewController.bands = #"hello world";
[myViewController release];
And in the header of MyViewController:
#interface MyViewController : UIViewController <UITableViewDataSource, UITableViewDelegate> {
NSString *bands;
}
#property (nonatomic, retain) NSString *bands;
That does not work, though.
Can anyone please tell me what I am doing wrong?
EDIT:
I synthesize bands in MyViewController:
#synthesize pageNumberLabel, tableProgram, bands;
But when trying to print it with NSLog in the viewDidLoad of MyViewController I get (null)
NSLog(#"%#", bands);
You need to synthesize the bands variable in MyViewController.m
#synthesize bands;
A variable needs to be synthesize in order to use it as a public property outsize of a class in Objective-C
I solved this in another way. I managed to load the data in MyViewController instead. I was dealing with a page controller and had to populate a UITableView but had troubles loading the data.
This is solved in a completely other way now.
Related
Ok, this is really bugging me and I am sure the solution is simple... I am unable to set my ViewController's property variables from another class (SeverConnect.m), which I have declared and synthesized properly in my ViewController's .h/.m files:
ServerConnect.h:
#import <Foundation/Foundation.h>
#import "ViewController.h"
#import "Contact.h"
#class ViewController;
#interface ServerConnect : NSObject
{
Contact *newContact;
NSString *codeRawContent;
NSMutableArray *contactListCopy;
... //Other variables declared here, but not shown in order to save space
Inside ServerConnect.m:
- (void)parserDidEndDocument:(NSXMLParser *)parser
{
NSLog(#"parserDidFinish");
newContact = [[Contact alloc] initWithCodeInfo:(NSString *)codeInfo
contactName:(NSString *)completeName
contactImage:(UIImage *)profileImage
contactWebSite:(NSString *)codeRawContent];
[contactListCopy insertObject:newContact atIndex:0];
[ViewController setContactList:contactListCopy]; //Automatic Reference Counting Error Occurs Here: "No known class method for selector 'setContactList:'"
}
As I mentioned above, I have declared and synthesized the property variable, "contactList", in my ViewController's .h/.m files (with no errors):
#property (nonatomic, retain) NSMutableArray *contactList; //In ViewController's .h file
#synthesize contactList; //In ViewController's .m file
Can someone tell me what I am doing wrong? Thanks in advance for any help you can provide!
you are trying to access an instance property on a class:
[ViewController setContactList:contactListCopy];
you need to first create an instance of the ViewController class, and then set its property. Something like this:
ViewController *viewController = [[ViewController alloc] init];
[viewController setContactList:contactListCopy];
In this line of code:
[ViewController setContactList:contactListCopy];
you should be using a variable of type ViewController. The way you are using it, it should be a class method, not a property.
Write something like:
ViewController *viewController = [[ViewController alloc] init];
[viewController setContactList:contactListCopy];
I'm having some trouble understanding how variable values are passed from one view to another. I have a UITextField in the firstview that the user enters a number into. When the user taps a button, that number is multiplied by 2 and the result is displayed on a UILabel in the second view. This is what I have thus far
FirstViewController.h
#interface FirstViewController : UIViewController{
UITextField *numberTextField;
NSNumber *aNumber;
}
#property (nonatomic, retain) IBOutlet UITextField *numberTextField;
#property (nonatomic) NSNumber *aNumber;
-(IBAction)calculate;
#end
FirstViewController.m
#implementation FirstViewController
#synthesize numberTextField, aNumber;
-(double)doubleNumber{
double number = [numberTextField.text doubleValue] * 2;
return number;
}
-(IBAction)calculate{
self.aNumber = [NSNumber numberWithDouble:[self doubleNumber]];
}
//more default code continues below
SecondViewController.h
#import "FirstViewController.h"
#interface SecondViewController : FirstViewController{
UILabel *numberLabel;
}
#property (nonatomic, retain) IBOutlet UILabel *numberLabel;
#end
SecondViewController.m
#implementation SecondViewController
#synthesize numberLabel;
- (void)viewDidLoad
{
[super viewDidLoad];
numberLabel.text = [NSString stringWithFormat:#"%#",aNumber];
}
Best and Easy Way to store value globally
set you object with your keyword
[[NSUserDefaults standardUserDefaults] setObject:#"Ajay" forKey:#"name"];
than get that object any where in you project
NSString *name = [[NSUserDefaults standardUserDefaults] objectForKey:#"name"];
You should accomplish what you want by using a segue. Create a segue in your storyboard and then call it in your firstviewcontroller with - (void)performSegueWithIdentifier:(NSString *)identifier sender:(id)sender. Then to pass data, import your secondviewcontroller.h file with a property for the value you want to pass and setup - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender.
In that method you can pass things by using [segue.destinationViewController ###call the setter for the property in your secondViewController.h file###];
If this isn't clear, or you need more help just let me know.
I'm assuming that the FirstViewController is instantiating the SecondViewController. If that is so, then you just pass aNumber to the SecondViewController using an additional property:
// add an additional property to the SecondViewController
#property (nonatomic, retain) NSNumber *aNumber;
When you instantiate the SecondViewController inside the FirstViewController, you just pass that value to the SecondViewController before you load it:
// inside FirstViewController
SecondViewController *secondViewController = [[SecondViewController alloc] initWithNibName:#"SecondViewController" bundle:nil];
secondViewController.aNumber = aNumber;
// inside SecondViewController
- (void)viewDidLoad
{
[super viewDidLoad];
numberLabel.text = self.aNumber;
}
Mmm... Pay attention to not confuse views and viewControllers!!!
A viewController can manage more than a view. For example in your code you have a UITextField, a UILabel and probably a UIButton. These are all views that are managed by two viewsController (FirstViewController and SecondViewController).
As long as you have so few views to work with you can use just one viewController and pass the value you want to your UILabel directly:
- (void)calculateAndPassValue
{
aNumber = [NSNumber numberWithDouble:[self doubleNumber]];
numberLabel.text = [NSString stringWithFormat:#"%#",aNumber];
}
Otherwise, if your goal is passing variable values from one viewController to another. Well... There are many ways you can obtain that, for example:
Creating an ivar.
Using a singleton.
Saving your data in NSUserDefault.
Creating a database on disk.
First and second cases are good if you need to manage your data while your app is running. Third and fourth if you want to memorize your data for future use and retrieve them at next start up.
Try to search keys like ivar, singleton, NSUserDefault and you'll find many discussions and lines of sample code.
I have my ViewController.h/m and another class Keyboard.h/m.
In my ViewController.h I have an UILabel:
#interface ViewController : UIViewController{
UILabel *label;
}
#property (nonatomic, retain) IBOutlet UILabel *label;
and my ViewController.m looks so
#import "ViewController.h"
#synthesize label;
...
Now I want to change the label from Keyboard.m.
I have tried something like this:
#import "ViewController.h"
...
ViewController *vc;
vc.label.text = #"text";
it compiles without any errors but the label doesn't change
It's very error prone that you're doing here.
ViewController *vc;
declares a pointer, but this won't be initialized; so when you're accessing its property vc.label.text, objc_messageSend() will be passed a bogus pointer, so it can potentially crash! (you're lucky if id didn't do so.)
Anyways: if you have done it well, like ViewController *vc = [[ViewController alloc] init]; creating a new instance wouldn't have affected the other instance. You have to store the pointer to your instance somewhere, e. g. set a #property (retain) ViewContrller *vc; to your application's app delegate object, and access it through that property like this:
[(MyAppDelegate *)[[UIApplication sharedApplication] delegate] vc].label.text = #"new text";
that way it should work.
Hope it helps.
How are you initiating your vc variable? I am guessing that is where the error is coming from. Try doing:
vc = [[ViewController alloc] initWithNibName:# ViewController"];
If you are already doing that, make sure your IBOutlet is hooked up correctly. You are setting the variable correctly so the error must be coming from somewhere else.
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 an iphone application containing two views
The first view have a button, now
i want to show the title of the button on the second view when that button is clicked.
How can i do it because if we save the title into a string ,the string get emptied when second view is loaded ?
In the interface declare the string and make a property:
#interface MyViewController : UIViewController {
NSString *string_i_want_to_set;
}
#property (nonatomic, retain) NSString *string_i_want_to_set;
#end
In the implementation synthesize the string after #implementation MyViewController like this:
#import "MyViewController.h"
#implementation MyViewController
#synthesize string_i_want_to_set;
// OTHER CODE HERE...
#end
Then when you alloc/init the view controller you can set the property like this:
MyViewController *myVC = [[MyViewController alloc] init];
myVC.string_i_want_to_set = #"...."
Hope this gives you more detail.
Thanks
James
you can make object of second view and can pass string to it
view2object.view2string=#"anything" or label.text;