I am making an app using a utility application template. I am trying to access the value of a UITextField from the FlipSideVewController class.
In the MainViewController.h file I have -
#interface MainViewController : UIViewController <UISplitViewControllerDelegate>{
UITextField *textField;
NSString *myText;
}
#property (retain, nonatomic) IBOutlet UITextField *textField;
#property (nonatomic, retain) NSString *myText;
-(IBAction)pressButton:(id)sender;
In the MainViewController.m file -
myText = [[NSString alloc] initWithFormat: textField.text];
NSLog(#"%#",myText);
I am creating the FlipSideViewController in the MainViewController class using the following code -
FlipsideViewController *controller = [[[FlipsideViewController alloc] initWithNibName:#"FlipsideViewController" bundle:nil] autorelease];
controller.delegate = self;
controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentModalViewController:controller animated:YES];
This prints the value of the textfield in the console without any problems. The problem happens when I try to access the value of the textfield in the FlipSideVewController class (after the user presses the go button).
In the FlipViewController class I have -
MainViewController *obj = [[MainViewController alloc] init ];
NSString *abc = obj.textField.text;
NSLog(#"%#",abc);
The FlipSideVewController nib file is loaded fine without any problems. However the console output is (null) when in FlipSideVewController.
I will appreciate any help.
Thanks
If you use the Utility Xcode template, you should think of MainViewController and FlipSideVewController as given: the framework will instantiate them for you and make it available to the rest of the program as you define (either in your code or in IB). What I mean by this is that your line:
MainViewController *obj = [[MainViewController alloc] init ];
does not really do what you want.
In your case, what you seems to want is access a text field controlled by the existing MainViewController instance (the one that gives you the NSLog output correctly) from your other existing FlipSideVewController instance. This is a matter of "connectin" somehow those two controllers.
There are several ways to accomplish this. One is defining a "model" for your app and have it shared between the controllers. See also the Model-View-Controller pattern. A model is just a data structure that contains your "data"; you make that data structure available to both of your controllers. The easiest way to create such data structure and have it shared is through a singleton (I am not suggesting to use it as the best way, just noting that it is the easiest way, IMO).
Another, less clean way is passing a reference to MainViewController to FlipSideVewController and then accessing the text field through it. By example, you could define an ivar in your FlipSideVewController, then, where the two controllers are created, you do the assignment to the ivar.
You should go to your MainViewController and declare your textField as a property first and synthesize it, so you can access it using obj.textField. And if you have just created obj using alloc and init, you wont have any text in the textField instance Variable.
MainViewController.h
#property (retain) UITextField *textField;
MainViewController.m
#synthesize textField;
and you could use
myText=textField.text;
Now this should do it and you can access this textField by obj.textField in your other class. But you still wont get its value if you are initializing it in your other class because you will be creating a brand new obj whose textField.text will be blank( unless you have overrided its designated initializer to set the textField.text value).
Declare NSString *abc as instance variable
NSString *abc;
and then as property
#property (copy) NSString *abc;
#synthesize abc;
After you create your FlipSideViewController,
controller.abc=myText;
Remove the code where you create obj.
This will do it.
Related
i have defined variable in GroupView.h
#interface GroupView()
{
NSMutableArray *chatrooms;
}
#end
#implementation GroupView
Now i want to pass this variable in segue
#interface FriendsViewController ()
#end
#implementation FriendsViewController
else if ([segue.identifier isEqualToString:#"showGroupView"]) {
GroupView *groupView = (GroupView *)segue.destinationViewController;
groupView.chatrooms = [NSMutableArray arrayWithArray:chatrooms];
}
i know that chatrooms has to be property in header file to code this way but it is not
So is there any way to use this variable in segue.
Thanks for help.
chatrooms defined as an ivar like you have done is accessed using -> notation:
groupView->chatrooms = [NSMutableArray arrayWithArray:chatrooms]
This is generally discouraged, though. You should use a property instead:
#interface GroupView
#property (strong) NSMutableArray *chatrooms;
#end
Incidentally, if you're using an NSMutableArray, that indicates that you want to modify the element list of the array directly and not just replace the array wholesale. If you only ever want to replace the array with a whole new array every time, I suggest using NSArray instead.
Another point to make here is that you're attempting to cast the object held at segue.destinationViewController as a GroupView. You have either named a UIViewController subclass in a very misleading way, or you are not accessing the GroupView as a correct member of the UIViewController that is returned to you.
Normally, if you are not building the SDK or something. You don't really have a better reason not to expose it in the header file. However, you can expose the property in the extension and declare a private property in the host class(It's really not able to pass if you just declare a local variable). For example, You have a extension called GroupView+Helper. So, you can pass it into the property exposed in the extension. And then internally translate into the GroupView.
In GroupView.m:
#interface GroupView
#property (strong, nonatomic) NSMutableArray *chatrooms;
#end
In GroupView+Helper.h
#property (strong, nonatomic) NSMutableArray *internalChatrooms;
Also, you need to import the GroupView+Helper in the GroupView.
It will make your chatrooms private and internalChatrooms protected.
I am trying to do the following, and not able to find a straightforward answer.. It is related to this :Passing uitextfield from one view to another. But not exactly.
I have a Firstview.m, from which I push to a Secondview.m. The Secondview.m has a UITextView. I allow the user to edit the UITextView on Secondview.m. Now I want to store this text value in a variable in Firstview.m. One way to to do this is as follows
in Firstview.h
#property (nonatomic) Secondview *secondView;
That is keep a secondView variable in Firstview itself. But this doesn't seem efficient. Ideally I should only have 1 NSString text field in FirstView. What is the right way to do this ? Thanks
You can achieve this by using Delegation in Objective-C.
In your SecondView.h add following right after Header Inclusion
#protocol YourDelegateName <NSObject>
-(void)setText:(NSString *)strData;
#end
Also add delegate property to your header for accessing them in calling class, like below (This goes with other properties declaration in SecondView.h file):
#property (nonatomic, weak) id<YourDelegateName> delegate;
Now, Comes the calling the delegate part. Say, you want to save the text value of UITextView of SeconView in strTextViewData of FirstView class, when the following event occurs:
- (IBAction)save:(id)sender
{
[self.delegate setText:self.txtView.text]; // Assuming txtView is name for UITextView object
}
Now, In FirstView.h add YourDelegateName in delegate list like below:
#interface FisrtView : ViewController <YourDelegateName>
#property (nonatomic, reatin) NSString *strTextViewData;
#end
And then in FisrtView.m file when you create instance of SecondView class, set delegate to self like below:
SecondView *obj = [[SecondView alloc] initWithNibName:#"SeconView" bundle:nil];
obj.delegate = self; // THIS IS THE IMPORTANT PART. DON'T MISS THIS.
Now, Implement the delegate method:
-(void)setText:(NSString *)strData
{
self.strTextViewData = strData;
}
Applying this to your code will do what you want. Also, Delegation is one of the most important feature of Objective-C language, which - by doing this - you will get to learn.
Let me know, if you face any issue with this implementation.
I'm trying this
SignUpViewController *userEmail=[[SignUpViewController alloc] init];
userEmail.emailAddress.text=email;
but is not working.
It seems like emailAddress (assuming UITextfeild) is not allocated properly when you called
SignUpViewController *userEmail=[[SignUpViewController alloc] init];
So, it is nil at the point of init.
Better way to do would be, added one public property in SignUpViewController of NSString. Save the value in that property. Like Below
SignUpViewController *userEmail=[[SignUpViewController alloc] init];
userEmail.emailString=email;
in SignUpViewController.h file add
#property (nonatomic, strong) NSString *emailString;
in SignUpViewController.m file in view did load
- (void)viewDidLoad{
//if you have not used nib or stroyboard init you textfield first
emailAddress.text=emailString;
}
Move your emailAddress #property into the .h file of SignUpViewController (Assuming you have an IBOutlet property set from Storyboard or Interface Builder
I think a better way of doing this is using a delegate to communicate between ViewControllers. See this answer for a quick example of creating a protocol for the delegate method, setting the second ViewController as the first one's delegate and then calling that method.
I have a main ViewController that contains a desginated class. Within that ViewController there is a Container that is linked to an embed ViewController. Within that embed ViewController I am creating an NSMutableArray. I am not trying to access that array inside the main ViewController. I know that if I use:
create_challenge_peopleSelect *myScript = [[create_challenge_peopleSelect alloc] init];
NSLog(#"%#",myScript.selectedCells);
The NSLog will output null because I am creating a new ViewController and that gets rid of the already set array. So my question is how can I access that array without overwriting it?
UPDATE:
Heres where the NSMutableArray is being created:
create_challenge_peopleSelect.h:
#property (strong, nonatomic) NSMutableArray *selectedCells;
create_challenge_peopleSelect.m:
if([selectedCells containsObject:label.text])
{
cell.accessoryType = UITableViewCellAccessoryNone;
[selectedCells removeObjectIdenticalTo:label.text];
}
else
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
[selectedCells addObject:label.text];
}
This class is the container class off the main ViewController
No I want to access the selectedCells within my main ViewController, I have been doing things such as:
create_challenge_peopleSelect *myScript = [[create_challenge_peopleSelect alloc] init];
I would prefer to stay away from the App Delegate If possible.
You seem to be unclear on the difference between classes and instances. OK, so, say we have two NSArrays:
NSArray *a = [[NSArray alloc] initWithObjects:#"hello", #"I", #"am", #"an", #"array", nil];
NSArray *b = [[NSArray alloc] initWithObjects:#"so", #"am", #"I", nil];
If I do a.count, I'll get 5 as the answer because the array contains five objects. Meanwhile, if I do b.count, I'll get 3, because that array contains three objects. It isn't that creating b "gets rid of the already set count". They are separate objects completely unrelated to each other.
Your view controller class is the same way. When you create a different instance, it doesn't overwrite the old one -- it's just not the same object. In order to use the original view controller object, you need to get a reference to it.
So how do you get a reference to it? Well, the general answer is you design your app so that the two objects know about each other. There are lots of specific ways to accomplish this. A lot of people will say "Just stick a reference in the app delegate." That is one thing you can do, but it's not always the best choice. It can get out of control if you just stick everything in your app delegate. Sometimes it's the right answer, often other things are the right answer. Another approach is to have an object that knows about both of those objects introduce them to each other. But sometimes there is no such object. So it's situational.
Basically, instead of creating a new view controller, you need to maintain a pointer to the original.
I suggest storing an instance of your UIViewController in the AppDelegate in order to retain the particular instance of the view controller you've created by making it a global variable.
ex. In the App Delegate.h
#import "ViewController.h"
#class ViewController;
#interface AppDelegate : UIResponder <UIApplicationDelegate>
#property (nonatomic) ViewController *viewController;
Then from whatever view controllers' .m's from which you need to read/write to the variable, create a pointer to the application's app delegate, ex:
#import "AppDelegate.h"
#interface WhateverViewController ()
AppDelegate *mainDelegate;
- (void)viewDidLoad {
mainDelegate = (AppDelegate*)[[UIApplication sharedApplication] delegate];
}
So wherever you first create that view controller in your code (before ever using it), initialize it using this global variable. ex. If you're using xibs:
mainDelegate.viewController = [[UIViewController alloc] initWithNibName:#"ViewController" bundle:nil];
[self.navigationController pushViewController:mainDelegate.viewController animated:YES];
ex. If you're using storyboards:
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:#"StoryboardName" bundle:nil];
mainDelegate.viewController = [storyboard instantiateViewControllerWithIdentifier:#"viewControllerID"];
[self.navigationController pushViewController:mainDelegate.viewController animated:YES];
(This is assuming it's in a place other than the app delegate in which case the pointer to the App Delegate isn't needed.)
Then when accessing the array from another UIViewController use
mainDelegate.viewController.array
To access the NSMutableArray from one class to another class use following code.
In the first view controller in which u have declared the object of NSMutableArray, declare the property and synthesize for the same as below,
//In FirstViewcontroller.h class,
#property (nonatomic, strong) NSMutableArray *arrData;
//In FirstViewcontroller.m class
#synthesize arrData;
Also FirstViewcontroller object should be global so you can create the object of FirstViewcontroller in app delegate file.
//appdelegate.h
#property (nonatomic, strong) FirstViewcontroller *objFirst;
//appdelegate.m
#synthesize objFirst;
FirstViewcontroller *objFirst=[[FirstViewcontroller alloc]init];
Now in SecondViewcontroller in which you have to access array,
create the share object of Appdelegate file
//SecondViewcontroller.m
AppDelegate *app = (AppDelegate*)[[UIApplication sharedApplication] delegate];
Then use will get the required array as below,
app.objFirst.arrData
This is your required array I hope it will help you.
The basic idea here is that in your original class, the array is referred to by a pointer. Your original class would allocate it and presumably load it. Other parts of your program can be handed the contents of the property, which is a pointer, assign that to their own pointer holder, and use it as if you had declared it there. Please use the above code;
MyClass *aClass = [[MyClass alloc] initWithMyInitStuff];
NSMutableArray *ThatArray = aClass.MyArray;
NSLog("Count of ThatArray: %d", [That.Array count]);
What you've done in the code provided is set a public property for a mutable array...
#property (strong, nonatomic) NSMutableArray *selectedCells;
The NSMutableArray is not "created" by setting that property. At some point in your code you also have to create the NSMutableArray by initialising...
NSMutableArray *selectedCells = [[NSMutableArray alloc] init];
or by using a convenience method such as...
NSMutableArray *selectedCells = [NSMutableArray arrayWithCapacity:(NSUInteger)<initialising capacity>];
or
NSMutableArray *selectedCells = [NSMutableArray arrayWithArray:(NSArray *)<initialising array>];
Initialising an NSMutableArray is often done only once. If it is repeated, the contents are overwritten against the property used to point to the array. As such, a useful location for this is often within the viewDidLoad view controller lifecycle method.
This is what I got so far.
mainview.m
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender(id)sender {
secondView *secView = [segue destinationViewController]
secView.ext = #".com";
}
secondView.h
#interface secondView : UIViewController {
NSString *ext;
}
#proper (nonatomic, retain) NSString *ext;
#end
secondView.m
-(void)viewDidLoad {
NSString *url = [#"www.google" stringByAppendingFormat:ext]
}
And its returning a error saying ext is null... what am I doing wrong?
Did you try to turn ext into a property instead? My understanding is that the "dot" notation essentially turns your code into
[secView setExt:#".com"]
So turn SecondView.h into
#interface secondView : UIViewController
#property (nonatomic, copy) NSString *ext;
#end
And don't forget to #synthesize it in your .m file
Check the followings:
Make sure #synthesize ext; is in SecondView.m
In Storyboard, have you linked the segue correctly?
In Stodyboard, is the viewController that represetns SecondView defined as a class of SecondView?
Make sure that you are calling the SecondView via prepareForSegue:sender method (i.e. SecondView doesn't get called by pushViewController:animated somewhere else in your code).
Put a breakpoint at the line:
secView.ext = #".com";
and make sure that the ext ivar is properly set after the assignment. If it's not, you might be specifying that the accessors use a different ivar in your #synthesize directive for ext, or you might have provided a setter -setExt: that doesn't properly set the ivar.
If ext is set properly after the assignment, perhaps you've got two different instances of secondView. That used to happen a lot when people used .xib files -- they'd create one view controller in code and have another instance of the same class in their .xib file. I wouldn't expect that to be the case here since you're getting secView straight from the segue, but it's worth thinking about.
There are two views: view1 and view2.
Add view2.h file in view1.h
init object of view2 and set their variable.