i want know if it's possible create a custom delegate in the AppDelegate class, like in this way for instance:
#protocol AppDelegateDelegate <NSObject>
- (void)finishSync:(BOOL)success;
#end
#interface AppDelegate : UIResponder <UIApplicationDelegate> {
#property (nonatomic, weak) id <AppDelegateDelegate> delegate;
#end
it's possible create something like this? to notify the classes that are registered for this delegate?
EDIT
How i can use the Delegate? for example if i do this:
#import "AppDelegate.h"
#interface MasterViewController : UIViewController <AppDelegateDelegate>
#end
.m
#implementation MasterViewController
...
- (void)viewDidLoad {
AppDelegate *appController = (AppDelegate *)[[UIApplication sharedApplication] delegate];
appController.customDelegate = self;
}
in i stay only in that view works, but for example if i switch in SecondViewController that have the same code to implement the delegate, the delegate don't works anymore neither in the MasterViewController...what i wrong?
Yes, That is fine. You can create delegates anywhere you want and use it anywhere by importing that class. There are no restrictions.
Related
Thanks in advance for your help!
In the main ViewController.m of my project I am adding a customized tableView like so:
messageController = [[MyMessagesController alloc] initWithStyle:UITableViewStylePlain];
[self addChildViewController:messageController];
[self.view addSubview:messageController.view];
Then, in the MyMessagesController.m section tableView didSelectRowAtIndexPath: I'd like to write code that would take effect in the ViewController.m where it was created and added as a childViewController.
How can I access the functions of the ViewController.m from MyMessagesController.m?
Can I make it a delegate somehow so I could call [delegate functionName];?
Could I pass information back to the ViewController.m? About which of the rows in table was selected by sending through an NSString or NSArray or anything?
Yes, use a delegate, if you are unsure how best to accomplish this, here is a good reference from Apple about delegate programming
Got it figured out, here's how you turn one viewController into a delegate for another:
In the .h of the parent controller -
#interface ViewController : UIViewController <NameOfDelegate> {
In the .m of the parent controller, once you create the new view -
newViewController.delegate = self;
and also:
- (void)functionToCall:(id)sender {
NSLog(#"Function Called!!!");
}
In the .h of the newViewController you're adding -
#protocol NameOfDelegate;
#interface newViewController : UIViewController/OR/TableViewController {
id <NameOfDelegate> delegate;
}
#property (nonatomic, strong) id <NameOfDelegate> delegate;
#end
#protocol NameOfDelegate
- (void)functionToCall:(id)sender;
#end
in the .m of the newViewController -
#implementation newViewController
#synthesize delegate;
and when you're ready to call the function in your delegate -
[delegate functionToCall:self];
I am a newbie to iPhone development and have some basic questions to ask about protocols and delegates. I have two view controllers: view controller and viewcontroller2nd. I have UITextField in one of them and would like to type something (like a name) in it and in the viewcontroller2nd, I have a UILabel and i would like it to appear Hello, name when the UITextField is changed.
I am following this video: http://www.youtube.com/watch?v=odk-rr_mzUo to get the basic delegate to work in a single view controller.
I am using protocols to implement this:
SampleDelegate.h
#import <Foundation/Foundation.h>
#protocol ProcessDelegate <UITextFieldDelegate>
#optional
- (BOOL)textFieldShouldReturn:(UITextField *)textField;
#end
#interface SampleDelegate : NSObject
{
id <ProcessDelegate> delegate;
}
#property (retain) id delegate;
#end
SampleDelegate.m
#import "SampleDelegate.h"
#implementation SampleDelegate
#synthesize delegate;
- (BOOL)textFieldShouldReturn:(UITextField *)textField{
lbl.text = [NSString stringWithFormat:#"Hello, %#",txtField.text];
[txtField resignFirstResponder];
}
#end
ViewController.h
#import <UIKit/UIKit.h>
#import "SampleDelegate.h"
#interface ViewController : UIViewController <ProcessDelegate>
{
IBOutlet UITextField *txtField;
}
#end
Viewcontroller.m
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
ViewController2nd.h
#import <UIKit/UIKit.h>
#interface ViewController2nd : UIViewController <ProcessDelegate> {
IBOutlet UILabel *lbl;
}
#end
and ViewController2nd.m is standard code from Xcode.
My question is how do i link my delegate function to my viewcontroller and viewcontroller2nd to get it working?
Pardon me if the question is stupid.. Need some guidance. Do point me any other mistakes that i am doing as well.. Thanks..
Your delegation is a bit... Off.
Firstly: Don't override UIKit delegate methods through protocol inheritance. It's pointless. Why not just make your class conform to the specified delegate in the first place?
#protocol ProcessDelegate //No more protocol inheritance!
//...
#end
Secondly: When an object has defined a protocol, a valid instance of that object must be in use by its delegate (or at least passed to it). So, anything that wants to be the delegate of SampleDelegate (really a bad name for a class, by the way) would initialize a valid SampleDelegate object, and call -setDelegate: as though it were any other property.
//#import "SampleDelegate"
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
//make this a property, so it isn't crushed when the function exits.
SampleDelegate *myDelegateObject = [[SampleDelegate alloc]init];
[myDelegateObject setDelegate:self]; //conform to the delegate
}
Thirdly: You don't actually define any delegate methods! What's the point of delegation if there's nothing to delegate!l
#protocol ProcessDelegate
-(void)someMethod;
#end
Fourth, and most important: Never, ever, ever, ever use the retain, or strong storage specifiers with a delegate! Delegate objects are supposed to be weak or assign to prevent nasty retain cycles.
#property (assign, nomatomic) id delegate;
I have a ViewController, and a UIView.
The UIView has a delegate, and the delegate function is set in the ViewController.
All I want to do, is have the delegate function defined in a separate file. So the UIView.m #imports the separate file, instead of all the ViewControllers which use the UIView.
I believe this is a standard procedure, but keep falling over myself trying to get it to work. :| Would really appreciate some help. Thanks.
myViewController.h
#import <UIKit/UIKit.h>
#import "myUIView.h"
#protocol ModalViewDelegate
-(void)didReceiveMessage:(NSString *)message;
#end
#interface myViewController : UIViewController <ModalViewDelegate>
#property (nonatomic, strong) myUIView *myUIViewItem;
#end
myViewController.m
#import "myViewController.h"
#import "myUIView.h"
#interface myViewController ()
#end
#implementation myViewController
#synthesize myUIViewItem;
- (void)didReceiveMessage:(NSString *)message { //<<< THIS IS WHAT
NSLog(#"Message from button: %#", message); //<<< NEEDS MOVING
}
- (void)viewDidLoad
{
…
myUIViewItem.delegate = self;
…
myUIView.h
#import <UIKit/UIKit.h>
#protocol ModalViewDelegate;
#interface myUIView : UIView {
id<ModalViewDelegate> delegate;
}
#property (nonatomic, strong) id<ModalViewDelegate> delegate;
myUIView.m
#import "myUIView.h"
#import "myViewController.h"
#implementation myUIView
#synthesize delegate;
...
[delegate didReceiveMessage:#"Data from UIView!"];
well, there is one method actually,
Just take one .h file and lets say connectionDelegate.h and declare your protocol init
In connectionDelegate.h:
#import <UIKit/UIKit.h>
#protocol ConnectionDelegate
-(void)getResult:(NSString*)_result;
#end
Then in your view controller:
#import "ConnectionDelegate.h"
#interface myViewController : UIViewController <ConnectionDelegate>
{
id delegate;
}
then in .m file, by just call the method
[delegate getResult:_result];
Edit regarding the warnings:
You need to declare the method in view controller, you need to do like this.
[self getResult:urlDataString];
-(void)getResult:(NSString*)_result{
[delegate getResult:_result];
}
Based on your comment:
I want to have the function 'didReceiveMessage' defined in a SEPARATE
file. So that I don't have to repeat it in every ViewController that
uses the UIView and delegate. e.g. ModalViewDelegate_Action.h and
ModalViewDelegate_Action.m
The way I was given was to use a subclass, and that's been working great for me. In my iOS projects I have a class called BaseViewController, which is a subclass of UIViewController. I put lots of code in it related to HUD management, NSOperations management, etc. Then virtually all my view controllers are subclasses of it.
I have created a tab based application having 4 tabs and 4 views respective to these tabs.
I have a string in first view and when I printing this string in second view it printing null.
In first view.h
NSString *dateString;
#property(nonatomic,retain) NSString *dateString;
In first view.m
#synthesize dateString;
dateString=button6.titleLabel.text;
NSLog(#"dateString:%#",dateString);
In second view.h
NSString *dateString;
#property(nonatomic,retain) NSString *dateString;
In second view.m
#synthesize dateString;
- (void)viewDidLoad { [super viewDidLoad];
NSLog(#"dateString:%#",self.dateString);
}
Add your view controllers as properties for the application delegate (if the app is a relatively simple design).
Then you can reference the properties of the second view controller from the first view controller, by way of the app delegate. (One such property could be the string you want the second VC to copy or retain.)
Create NSString variable in Application delegate class and set the Property and make synthesize that variable.
And set the #"" (blank) value in applicationDidFinishLaunching method.
For Example - my variable name is str, then initialize str in applicationDidFinishLaunching like self.str = [NSString stringWithFormat:#""];
And now you can use it in any tab *view* and set the value as per your require.
More code
AppDelegate.h
#interface AppDelegate : NSObject <UIApplicationDelegate> {
UIWindow *window;
NSString *baseURL;
}
#property (nonatomic, retain) NSString *baseURL;
#end
AppDelegate.m
#import "AppDelegate.h"
#implementation AppDelegate
#synthesize window;
#synthesize baseURL;
- (void)applicationDidFinishLaunching:(UIApplication *)application {
self.baseURL = [NSString stringWithFormat:#""];
}
- (void)dealloc
{
[baseURL release];
[window release];
[super dealloc];
}
#end
ViewController1.h
#class AppDelegate;
#interface ViewController1 : UIViewController <UITextFieldDelegate>
{
AppDelegate *appDelegate;
}
#end
ViewController1.m
#import "AppDelegate.h"
#import "ViewController1.h"
#implementation ViewController1
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
[super viewDidLoad];
appDelegate = (AppDelegate*)[[UIApplication sharedApplication] delegate];
NSLog(#"value - %#",appDelegate.baseURL); // Here you can set or get the value.
}
it may not be the best answer.but creating a string variable in the appdelgate and passing the variable to this from the first view and fetching it from the second view works for me
Really, did we lose focus of MVC and the most awesome of abilities that is easy to do in iPhone Development?
How about a delegate?
#protocol ViewOneDelegate
- (void)getStringVariable;
#end
#interface ViewOneModel : NSObject
{
NSString* _stringVariable;
id<ViewOneDelegate> _theDelegate;
}
#property (nonatomic, retain) id<ViewOneDelegate> theDelegate;
#end
Assign a controller to be the delegate for the ViewOneModel.
Here is a simple solution, but not the best one, Create a global variable, and just use that.
Header
extern NSString *GlobalString;
#interface GlobalVariables : NSObject {
}
#end
implementation
#import "GlobalVariables.h"
#implementation GlobalVariables
NSString *GlobalString;
#end
And now to have access to the variable just import the header in the file you want to use.
You'll probably want to check if it's initiated before you use it.
I have a class like this..
#import "MyObjectAddView.h"
#import "MyAppDelegate.h"
#define myAppDelegate (MyAppDelegate *) [[UIApplication sharedApplication] delegate]
#class MyObjectAddView;
#interface AccountViewController : UIViewController <UIScrollViewDelegate, MyObjectAddViewDelegate, UIImagePickerControllerDelegate> {
MyObjectAddView *myAddView;
.....
}
#property (nonatomic, retain) IBOutlet MyObjectAddView *myAddView;
- (id) initWithSettings:(SettingsObject *)settings;
#end
WHY is it suddenly telling me that it Cannot find protocol declaration for 'MyObjectAddViewDelegate' when I'm clearly importing and including the #class for where the protocol is defined? Here how MyObjectAddView setup:
#import <UIKit/UIKit.h>
#import "MyAppDelegate.h"
#define myAppDelegate (MyAppDelegate *) [[UIApplication sharedApplication] delegate]
#protocol MyObjectAddViewDelegate;
#interface MyObjectAddView : UIView <UITextFieldDelegate> {
#private
id <MyObjectAddViewDelegate> delegate;
....
#public
.....
}
#property(nonatomic, assign) id <MyObjectAddViewDelegate> delegate;
.....
#end
#protocol MyObjectAddViewDelegate <NSObject>
// expense == nil on cancel
- (void)myObjectAddViewDidFinish:(MyObjectAddView *)addView;
#end
Everything seems perfectly setup and I don't see any circular imports ?! Any suggestions why it might not be seeing the protocol definition in MyObjectAddView?
Thanks.
You do not need a forward reference to a class after you have imported the header for that class. Only time you do a forward reference is if you plan on including the header inside of the implementation file. Remove #class MyObjectAddView and if that fixes it let me know if not I may have another solution for you.
Synthesizing the discussion: another solution is to check for cyclical imports between the delegate implementation and protocol declaration. This solved my issue.