I have a function that returns a NSUrl, and i want to use it in another class. But when i tried to retrieve it in my other class, it gives me null.
This is my First Class
#interface UOEventDetailController : UIViewController {
NSURL *imgData;
}
#property(nonatomic, retain)NSURL *imgData;
-(NSURL *)imgData;
#implementation UOEventDetailController
#synthesize imgData;
The .m File
-(NSURL *)imgData{
UOEventPost *post = (UOEventPost *)self.event;
NSURL *url = [NSURL URLWithString:post.postImageURL];
return url;
}
I want to retrieve the URL in this class
#class UOEventDetailController;
#interface UOEnlargeImageViewController : UIViewController {
IBOutlet UIImageView *enlargedImage;
}
#property (nonatomic, retain) UOEventDetailController *controller;
#property (nonatomic, retain) IBOutlet UIImageView *enlargedImage;
the .m file
#implementation UOEnlargeImageViewController
#synthesize controller;
#synthesize enlargedImage;
- (void)viewDidLoad
{
[super viewDidLoad];
self.title = #"Enlarged Image";
controller = [[UOEventDetailController alloc]init];
NSURL *url = [controller imgData];
NSLog(#"%#",url);
}
#end
I can retrieve objects other than post.postImageUrl.
For Example
instead of post.postImageUrl, i put in string like #"omg", #"god"
it gets retrieved in my other class...
EDIT
-(IBAction)enlargeImg{
UOEventPost *post = (UOEventPost *)self.event;
UOEnlargeImageViewController *enlarge = [[UOEnlargeImageViewController alloc]initWithNibName:nil bundle:nil];
enlarge.temp = post.postImageURL;
[self.navigationController pushViewController:enlarge animated:YES];
[suggestPopupView removeFromSuperview];
[enlarge release];
}
this is because you are making a new object. and that of new object, relevent attributes are empty and hence url is also null.
The Object will be null as a new object is being created and it's not in same state as you want it , you must use protocol & delegate to pass the object to another class if flow is backward else ensure that you work on the same object.
Related
I have to pass a UITextField value from one view to other views(2nd,3rd...views).Actually in my 3rd ViewController I have a scrollView and I have to display value on it .But UITextField value is not getting passed.It is returning null.Couldn't get what might be wrong?
THis is the code I am working with:
In ViewController1.m:
-(IBAction)butonclick:(id)sender{
ViewController2 *view2=[ViewController2 alloc];
view2.id=name.text;
ViewController3 *view3=[ViewController3 alloc];
view3.id=name.text;
[view2 release];
[view3 release];
}
IN ViewConroller2.h :
#interface ViewController2 : UIViewController {
NSString *id;
UIlabel *displayId;
}
In ViewController2.m :
- (void)viewDidLoad
{
self.displayId.text=self.id;
}
In ViewController3.h:
#interface ViewController2 : UIViewController {
NSString *id;
UIlabel *dispId;
}
In ViewController3.m :
- (void)viewDidLoad
{
self.dispId.text=self.id;
}
But here the id value is not passed to ViewController3.It is returning null ..Where I m going wrong?
You are passing the values without initializing.
ViewController2 *view2=[[ViewController2 alloc]init];
view2.id=name.text;
ViewController3 *view3=[[ViewController3 alloc]init];
view3.id=name.text;
If you want to use object globally within your app, you can declare it in the appDelegate.
In AppDelegate.h
#interface AppDelegate : NSObject <NSApplicationDelegate>
{
NSString *idGlobal;
}
#property (nonatomic, retain) NSString *idGlobal;
In AppDelegate.m
#synthesize idGlobal;
In ViewController1.m:
-(IBAction)butonclick:(id)sender{
appDelegate.idGlobal=name.text;
}
In ViewController2.m: and
In ViewController3.m:
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
id=appDelegate.idGlobal;
Declare the string globally in the AppDelegate.h this will help in keeping the value of the string constant throughout the files. Also wherever you want to add the string or change its value or assign it import the AppDelegate.h .
Also check these links :-
passing NSString from one class to the other
Pass NSString from one class to another
I am just correcting the code you have written meanwhile the suggestions given above for using AppDelegate property is a good one.
The main problem with your code is that you are just declaring NSString object instead of making it a property. Check this:
-(IBAction)butonclick:(id)sender{
ViewController2 *view2=[ViewController2 alloc]init];
view2.str=name.text;
ViewController3 *view3=[ViewController3 alloc]init;
view3.str=name.text;
[view2 release];
[view3 release];
}
IN ViewConroller2.h :
#interface ViewController2 : UIViewController {
NSString *str;
UIlabel *displayId;
}
#property(nonatomic, retain) NSString* str; //Synthesize it in .m file
In ViewController2.m :
- (void)viewDidLoad
{
self.displayId.text=self.str;
}
In ViewController3.h:
#interface ViewController2 : UIViewController {
NSString *str;
UIlabel *dispId;
}
#property(nonatomic, retain) NSString* str; //Synthesize it in .m file
In ViewController3.m :
- (void)viewDidLoad
{
self.dispId.text=self.str;
}
I am not aware with your scenario but the most effective way of implementing such situations is using Delegates. Make a delegate of the class where your string is being set (ViewController1) and set delegate accordingly in your other view controllers.
I'm setting a string in a view controller called ViewController and trying to access it somewhere else. This is the code:
ViewController.h
NSString *string;
...
#property (retain) NSString *string;
ViewController.m
#synthesize string;
...
-(void)viewDidLoad {
...
string = #"Test";
}
OtherViewController.m
#import "ViewController.h"
...
-(void)viewDidLoad {
ViewController *vc;
vc = [[ViewController alloc] init];
NSLog(#"String: %#", vc.string);
}
However, the log is showing: String: (null). What am I doing incorrectly? Thanks.
The viewDidLoad of ViewController is only called when the view is loaded. The view is lazily loaded when required e.g. when a call to vc.view is made.
I'm not sure what you are trying to achieve but this certainly seems like a code smell to me.
As #Fscheidl points out you are creating a new instance and not accessing an existing instance so this may add to your problem. I still believe your main issue is that you assume viewDidLoad is being called just by creating the viewController, which is not the case
edit : it doesn't necessarily need to be an NSObject class, if you want to, you could also do this on your viewController class, just be sure to also include
-(id)init
on your header
---- end of edit
if you're trying to make a class that's accessible to another view controller, why not try NSObject instead of view controller (considering you only need to take that string value)
for instance, lets call that viewController class "global" class
so at global.h, you put up
#import <Foundation/Foundation.h>
#interface GlobalVar : NSObject
#property (nonatomic, strong) NSString *myString;
-(id)init;
#end
and then, at global.m you put up
#import "GlobalVar.h"
#implementation GlobalVar
#synthesize myString;
-(id)init
{
self = [super init];
if(self)
{
myString = [[NSString alloc]initWithFormat:#"the String"];
}
return self;
}
#end
after this, everytime you need to access the "myString" object that contained in global class, you could put up
at header :
#import "GlobalVar.h"
...
...
#property (nonatomic, strong) GlobalVar *globalVar;
at implementation file :
#synthesize globalVar;
...
...
self.globalVar = [[GlobalVar alloc]init];
NSString *theString = globalVar.myString;
NSLog(#"content of my string is : %#",theString);
there you go ;)
You do create a new instance of ViewController by calling [[ViewController alloc] init]; This instance hasn't had string even set. You have to access that exact instance of ViewController.
If you create the instance of OtherViewController directly from ViewController, you can add the following to OtherViewController.h:
#import "ViewController.h"
#property (nonatomic, retain) ViewController *previousViewController
When creating the OtherViewController, you can then set:
//alloc and init instance of OtherViewController
myOtherViewController.previousViewController = self;
In your viewDidLoad: method, you can then access your string as follows:
NSLog(#"String: %#", previousViewController.string);
hi i am new to iphone development.
I'm trying with sample where I need to copy a string from the textfield of viewController and display it on the next view with a Label.
On the first view there is button bellow the textfield.1
I am not able to fix some issues showing BAD ACESS can anyone help me in solving this.
Let me know what i'm doing Wrong.
Thank you.
//copystring.h
#interface CopystringViewController : UIViewController{
UITextField *myTextField;
NSString *somestring;
}
#property(nonatomic,retain)IBOutlet UITextField *myTextfield;
#property(nonatomic,retain)NSString *somestring;
-(IBAction)next:(id)sender;
//.m file
#synthesize myTextfield,somestring;
-(IBAction)next:(id)sender;
{
NextView * next = [[NextView alloc] initWithNewString: myTextField.text];
[self.navigationController presentModalViewController: next animated: YES];
}
NextView.h
#interface NextView : UIViewController{
UILabel *string2;
}
#property(nonatomic,retain)IBOutlet UILabel *string2;
- (id)initWithNewString:(NSString*)someString;
//.m file
#synthesize string2;
-(id)initWithNewString:(NSString*)someString {
string2 = someString;
return self;
}
Just replace method.it may run.
-(IBAction)next:(id)sender; {
NextView * next = [[NextView alloc] initWithNibName:#"NextView" bundle:nil];
next.string2=myTextField.text;
[self.navigationController presentModalViewController:next animated: YES];
}
hey string2 is a label so try string2.text = somestring;
-(id)initWithNewString:(NSString*)someString {
string2.text = someString;
return self;
}
It looks like the problem is that you're assigning an NSString (someString) to a UILabel (string2).
AppleVijay's answer should do the trick.
If you don't like dot-notation in ObjC you can also write it like this:
[string2 setText:someString]
U can declare ur somestring in to the delagate h/m file that way it wil be the global string. u can use it with appdaligateobj.stringname.
U dont evn need init u can directly add to viewdidload of next view.
string2.text = AppDalegateobj.stringName.
Delegation is the usual way to move data around like this. I wrote a very simple example project to show this in action.
You need init you view and retain you string:
-(id)initWithNewString:(NSString*)someString {
self = [super init];
if (self) {
string2.text = someString;
}
return self;
}
/
/AppDelegate.h
NSString *String1;
#property (nonatomic, retain) NSString * String1;
//AppDelegate.m
#synthesize String1
//ViewController1.h
AppDelegate * objAppDelegate;
UILable *lblstring;
#property (nonatomic, retain) UILable *lblstring;
//ViewController1.m
#synthesize lblstring
//On View Did Load.
objAppDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
lblstring.text = objAppDelegate.String1;
I'm new to Objective C and I'm having trouble getting delegates to work in my code.
I have a class called cViewController and in this class has a UIWebView to fetch webpages and a button above it that calls a popover class called prodMenu. What I'm having trouble with is that the function to call webpages from the prodMenu class and display it on the parent UIWebView isn't working.
cViewController.h
#import <UIKit/UIKit.h>
#import "prodMenu.h"
#interface cViewController : UIViewController <prodMenuDelegate>{
UIPopoverController *cpopover;
IBOutlet UIWebView *webImageDisplay;
}
#property (nonatomic, retain) UIWebView *webImageDisplay;
#property (nonatomic, retain) UIPopoverController *cpopover;
- (IBAction)cPopoverTapped:(id)sender;
- (void) fetchWebsite:(NSString *)website; //This is the delegate method I'm trying to call in the popover class.
#end
cViewController.m
- (IBAction)cPopoverTapped:(id)sender {
prodMenu *tp = [[prodMenu alloc] init];
cpopover = [[UIPopoverController alloc] initWithContentViewController:tp];
[tp release];
CGRect rect = CGRectMake(40, 0, 50, 50);
cpopover.popoverContentSize = CGSizeMake(250, 225);
[cpopover presentPopoverFromRect:rect inView:self.view permittedArrowDirections:UIPopoverArrowDirectionUp animated:YES];
}
- (void)fetchWebsite:(NSString*)website{ //This function is called by prodMenu class
NSLog(#"address: %#", website);
NSString *urlAddress = website;
NSURL *url = [NSURL URLWithString:urlAddress];
NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
[webImageDisplay loadRequest:requestObj];
[webImageDisplay release];
}
- (void)viewDidLoad {
[self fetchWebsite:#"http://www.yahoo.com"];
[super viewDidLoad];
}
prodMenu.h
#import <UIKit/UIKit.h>
#protocol prodMenuDelegate;
#interface prodMenu : UIViewController{
<prodMenuDelegate> delegate;
}
- (IBAction)radBtn:(id)sender; //This is the IBAction that calls the fetchWebsite function
#property (nonatomic, assign) id <prodMenuDelegate> delegate;
#end
#protocol prodMenuDelegate
- (void)fetchWebsite:(NSString *)website;
#end
prodMenu.m
#import "prodMenu.h"
#import "cViewController.h"
#implementation prodMenu
#synthesize delegate;
- (IBAction)radBtn:(id)sender{
[delegate fetchWebsite:#"http://www.google.com"]; //Here is the call to the method
}
Am I missing something here to call the delegate method? There aren't any errors or warnings. All I want to do is when the user presses a button on the popover view, the parent class underneath changes the webpage. Thanks in advance.
Just a quick idea. Have you tried declaring the delegate protocol like this
#protocol prodMenuDelegate <NSObject>
...
#end
? I often ran into troubles when omitting the < NSObject >. Also I think there is an 'id' missing in
#interface prodMenu : UIViewController{
<prodMenuDelegate> delegate;
}
Edit: Also, in the code you posted I do not see where you actually assign the prodMenu's delegate.
Scenario: Need to execute CustomWebview delegate on view controller.
Please help me with this code. Instead of using callback, I need to use "Protocol". Can it be done or we can only use callback in this scenario.
On ViewController.m
- (void)viewDidLoad
{
[super viewDidLoad];
//MyWebView *webView = [[MyWebView alloc] initWithDelegate:self callback:#selector(finishLoading)];
MyWebView *webView= [[MyWebView alloc] initWithFrame:CGRectMake(0,0,320, 460)];
[webView LoadURL:#"http://192.168.5.165/"];
[webView setDelegate:self];
[webView setCallback:#selector(finishLoading)];
[self.view addSubview:webView] ;
}
- (void) finishLoading
{
NSLog(#"Finish");
}
On MyWebView.h
#interface MyWebView : UIView<UIWebViewDelegate> {
NSString *strURL;
}
#property(nonatomic, retain) NSString *strURL;
#property (nonatomic, assign) id delegate;
#property (nonatomic, assign) SEL callback;
-(void) LoadURL:(NSString*)url;
#end
On MyWebView.m
#import "MyWebView.h"
#implementation MyWebView
#synthesize strURL,delegate,callback;
UIWebView *webView;
-(id) initWithFrame:(CGRect)frame
{
if(self =[super initWithFrame:frame])
{
webView = [[UIWebView alloc] initWithFrame:frame];
webView.delegate = self;
[self addSubview:webView];
}
return self;
}
-(void) LoadURL:(NSString*)url
{
NSURL *u = [NSURL URLWithString:url];
NSURLRequest *req= [NSURLRequest requestWithURL:u];
[webView loadRequest:req];
}
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
[delegate performSelector:callback];
}
Your question is a bit unclear. A protocol and a delegate are two entirely separate, though related, things--apples and oranges. A protocol defines a list of methods an object may or must respond to:
#protocol Document
+ (id)documentWithContentsOfURL: (NSURL *)aURL;
- (void)writeToURL: (NSURL *)aURL error: (NSError **)outError;
#end
A delegate is an object, usually an instance of a custom class, that is handed to another object for custom processing or feedback--that latter object delegates work to the delegate object.
Are you asking how to convert a delegate category on NSObject to a delegate protocol? (The former used to be Apple's pattern for defining the obligations and abilities of a delegate; the latter is the newer way to do the same thing.) If so, it generally looks something like this:
Delegate Category on NSObject
#interface NSObject (WidgetDelegate)
- (void)doSomethingWithWidget: (Widget *)w;
#end
#interface Widget : NSObject
#property (readwrite, assign) id delegate;
#end
Delegate Protocol
#protocol WidgetDelegate <NSObject>
- (void)doSomethingWithWidget: (Widget *)w;
#end
#interface Widget : NSObject
#property (readwrite, assign) id <WidgetDelegate> delegate;
#end
Is that what you're looking for? If not, can you clarify exactly what you're trying to do?
Also see Apple's Communicating with Objects, which discusses delegates, protocols, and selectors. Though its listed under Mac OS X, most (if not all) appears to apply to iOS also.
On ViewController.m
#interface MyViewController : UIViewController<MyFinishLoadingDelegate> {
//your own definition
}
- (void)viewDidLoad
{
[super viewDidLoad];
//MyWebView *webView = [[MyWebView alloc] initWithDelegate:self callback:#selector(finishLoading)];
MyWebView *webView= [[MyWebView alloc] initWithFrame:CGRectMake(0,0,320, 460)];
[webView LoadURL:#"http://192.168.5.165/"];
[webView setDelegate:self];
[self.view addSubview:webView] ;
}
- (void)finishLoading //this is your implementation for MyFinishLoadingDelegate
{
NSLog(#"Finish");
}
On MyWebView.h
//you declare the protocol here to tell anyone who'd like to act like your delegate that they need to implement "finishLoading"
#protocol MyFinishLoadingDelegate <NSObject>
- (void)finishLoading;
#end
#interface MyWebView : UIView<UIWebViewDelegate> {
NSString *strURL;
}
#property(nonatomic, retain) NSString *strURL;
#property (nonatomic, assign) id<MyFinishLoadingDelegate> delegate;
-(void) LoadURL:(NSString*)url;
#end
On MyWebView.m
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
[delegate finishLoading];
}