I'm new to objective-c and, maybe I haven't grassped the concept of delegation very clearly yet, but i hope to do it by using it. I'm trying to implement a delegation in my app.
Idea is that i have class TableViewController which has NSMutableArray used for TableView initialization. I need to reinitialize this Array from my DropDown class. I'v tried to do that using delegation but failed to do it yet, maybe there is something wrong with it. I could pass TableViewController to DropDown class and edit the table via object. But i'd like to get it done using delegation.
Here is my TableViewController.h
#protocol TableViewControllerdelegate;
#interface TableViewController : UIViewController<UITableViewDataSource,UITableViewDelegate,MFMessageComposeViewControllerDelegate>
{
ControllerType controllerType;
}
#property (retain, nonatomic) IBOutlet UITableView *tableView;
#property (retain, nonatomic) NSMutableArray *dataArray;
#property (retain, nonatomic) NSArray *imageArray;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil andType:(ControllerType)type;
- (void)sendSMS: (NSString *) sms;
#end;
Here is my DropDown.h
#import "TableViewController.h"
#interface DropDownExample : UITableViewController <VPPDropDownDelegate, UIActionSheetDelegate> {
#private
VPPDropDown *_dropDownSelection;
VPPDropDown *_dropDownSelection1;
VPPDropDown *_dropDownSelection2;
VPPDropDown *_dropDownSelection3;
VPPDropDown *_dropDownSelection4;
VPPDropDown *_dropDownDisclosure;
VPPDropDown *_msg;
VPPDropDown *_dropDownCustom;
NSIndexPath *_ipToDeselect;
}
+ (bool) uncheck:(UITableViewCell *) cell andData:(NSString *) data;
- (void)reloadData;
#end
And this is how i try to edit my tableview object array
TableViewController *newControll = (TableViewController*)[UIApplication sharedApplication].delegate;
NSMutableArray *arrayWithInfo = [[NSMutableArray alloc] initWithObjects:AMLocalizedString(#"Status", nil),AMLocalizedString(#"Call", nil),AMLocalizedString(#"Location", nil),AMLocalizedString(#"Control", nil),AMLocalizedString(#"Sim", nil),AMLocalizedString(#"Object", nil),AMLocalizedString(#"Info", nil),nil];
newControll.dataArray = arrayWithInfo;
[arrayWithInfo release];
[newControll.tableView reloadData];
I get it running, but it get's '-[AppDelegate setDataArray:]: unrecognized selector sent to instance after reaching this code.
OK, I am not sure if I got this right but it finally clicked for me what delegation is and why I need it. Hopefully you'll understand too once you read through my scenario.
History
Previously, in my UITabBar app, I wanted to show a custom form view overlaid on top of my view controller to enter name and email.
Later I also needed to show the same custom overlay on top of another view controller on another tab.
At the time I didn't really know what delegation was for, so the first method I used to tackle this problem was NSNotificationCenter. I duplicated the same code to my second view controller and hooked it up to a button press event.
On pressing a button on the second view controller on another tab, it certainly showed my custom overlay, just like my first view controller.
However, this is where the problem starts.
The Problem
I needed to close my custom form view. So using NSNotificationCenter, I posted a notification and the listener callback method for the notification was told to close my custom view.
The problem was, using NSNotificationCenter, all listeners both in my first tab and my second tab responded to the posted notification and as a result, instead of closing just the custom form view overlaid on top of my second view controller, it closed ALL my custom view, regardless of where the custom view was opened from.
What I wanted was when I tap on the "X" button to close my custom form view, I only want it to close it for that single instance of the custom view, not all the other ones I had opened.
The Solution: Delegation
This is where it finally clicked for me - delegation.
With delegation, I tell each instance of my custom form view who the delegate was, and if I was to tap on the "X" button to close my custom view, it only close it for that single instance that was opened, all the other view controllers were untouched.
Some Code
Right, down to some code.
Not sure if this is the best way to do it (correct me if I am wrong) but this is how I do it:
// ------------------------------------------------------------
// Custom Form class .h file
// ------------------------------------------------------------
#protocol MyCustomFormDelegate <NSObject>
// if you don't put a #optional before any method, then they become required
// in other words, you must implement these methods
-(void)sendButtonPressed;
-(void)closeButtonPressed;
// example: these two methods here does not need to be implemented
#optional
-(void)optionalMethod1;
-(void)optioinalMethod2;
#end
#interface MyCustomFormView : UIView
{
...
id<MyCustomFormDelegate> delegate;
}
...
#property (nonatomic, retain) id<MyCustomFormDelegate> delegate;
#end
// ------------------------------------------------------------
// Custom Form class .m file
// ------------------------------------------------------------
...
#implementation TruckPickerView
#synthesize delegate;
-(id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if(self)
{
...
[btnSend addTarget:self selector:#selector(sendEmail) forControlEvent:UIControlEventTouchUpInside];
...
[btnClose addTarget:self selector:#selector(closeForm) forControlEvent:UIControlEventTouchUpInside];
}
return self;
}
-(void)sendEmail
{
// code sends email
...
// ------------------------------------------------------------
// tell the delegate to execute the delegate callback method
//
// note: the implementation will be defined in the
// view controller (see below)
// ------------------------------------------------------------
[delegate sendButtonPressed];
}
-(void)closeForm
{
// ------------------------------------------------------------
// tell the delegate to execute the delgate callback method
//
// note: the implementation will be defined in the
// view controller (see below)
// ------------------------------------------------------------
[delegate closeButtonPressed];
}
// ------------------------------------------------------------
// view controller .h file
// ------------------------------------------------------------
#import "MyCustomFormView.h"
// conform to our delegate protocol
#interface MyViewController <MyCustomFormDelegate>
{
...
// create a single instance of our custom view
MyCustomFormView *customForm;
}
#property (nonatomic, retain) MyCustomFormView *customForm;
// ------------------------------------------------------------
// view controller .m file
// ------------------------------------------------------------
#synthesize customForm;
-(void)viewDidLoad
{
customForm = [[MyCustomFormView alloc] initWithFrame:....];
// tell our custom form this view controller is the delegate
customForm.delegate = self;
// only show the custom form when user tap on the designated button
customForm.hidden = YES;
[self.view addSubview:customForm];
}
-(void)dealloc
{
...
[customForm release];
[super dealloc];
}
// helper method to show and hide the custom form
-(void)showForm
{
customForm.hidden = NO;
}
-(void)hideForm
{
customForm.hidden = YES;
}
// ------------------------------------------------------------
// implement the two defined required delegate methods
// ------------------------------------------------------------
-(void)sendButtonPressed
{
...
// email has been sent, do something then close
// the custom form view afterwards
...
[self hideForm];
}
-(void)closeButtonPressed
{
// Don't send email, just close the custom form view
[self hideForm];
}
You get that error, because (as the error says) you're sending a setDataArray: message to your app delegate (the AppDelegate class).
[UIApplication sharedApplication].delegate;
This will return the delegate of you app. There are a couple of ways to find out which class is your app's delegate, but usually it's called AppDelegate (as in your case) and it's implementing the UIApplicationDelegate protocol too.
You can't simply cast that to a completely different class. If your app delegate has an ivar or property of type TableViewController you have to use accessors to get it. If it's a property, you can use the dot notation. If it's an ivar, you can either implement a getter method that returns the ivar, or make it a property instead.
// assuming your app delegate has a TableViewController property called myTableViewController.
AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
TableViewController *tableViewController = appDelegate.myTableViewController;
This will fix the error, but your use of the delegate pattern is wrong too. I don't see where you're using any custom delegates. You forward declare a TableViewControllerdelegate protocol, but I don't see any declaration of it, or I don't see where you're trying to use it.
Related
I am working on a front end for a project in objective-c and I am having some trouble getting methods of my class Window which is a subclass of NSViewController to fully execute when called from a different class.
I have a method of the class Window that is called setColor which changes the color of my NSTableView variable which is linked to a bordered scroll view in my interface. I am able to successfully change the color by calling the setColor method like this from the init method in Window: [self setColor :self];
However when I do this [window1 setColor: window1] with window1 being an object of the class Window that I have declared in class Door, nothing seems to happen since the color of the boarded scroll view remains the same.
My Window.h file looks like this:
#interface Window : NSViewController {
#public
IBOutlet NSTableView *dataTableView;
}
#property (retain) IBOutlet NSTableView *tableView;
- (IBAction)SetColor:(id)sender;
#end
My Window.m looks like this:
#synthesize tableView;
- (void) awakeFromNib {
// [self SetColor :self];
}
- (IBAction)SetColor:(id)sender;
{
NSLog(#"changing the color");
[self->tableView setBackgroundColor: NSColor.blueColor];
}
Door.h looks like this
#interface Door : NSViewController {
Window* window1;
}
-(IBAction)buttonPress:(id)sender;
#property (retain) Window* window1;
#end
Door.m looks like this:
-(void) dealloc{
[window1 release];
}
-(id)init{
self = [super init];
if(self){
window1 = [Window alloc];
}
-(IBAction)buttonPress :(id)Sender;
{
[window1 setColor: window1];
}
I am using Xcode 3.2 so I cannot use ARC.
window1 = [Window alloc] will not load a Nib or storyboard and connect the outlet IBOutlet NSTableView *dataTableView to the table view inside it.
If "Window" is a view controller, you need to initialize it and the outlets in it a more standard way. View controllers need the proper initialization or the outlets are nil, and in Objective-C, if you send a method to nil, it just does nothing.
I have a table view in my previous view which is get data from an array in my app. I have a view to update data which is push on cell select. Once data is updated in the view i call
[self.navigationController popViewControllerAnimated:YES];
to go back to previous view. But the label get stacked with old and new data I don't know why... If I go one view back and come back again to the tableview everything is fine only new data is shown..
So I guess I have to rebuild view to avoid the problem. Is this possible ?
Your question initially asked about rebuilding a controller, so here's the answer to that:
I'm assuming that your have a navigation stack like this:
An instance of FirstController
An instance of SecondController
An instance of ThirdController
A thing happens in your third controller, and you now want the stack to look like this:
An instance of FirstController
A new instance of SecondController
The first thing to do is to define a delegate protocol for ThirdController, in your header file like this:
#protocol ThirdControllerDelegate;
#class ThirdController : UIViewController
#property (nonatomic, weak) id<ThirdControllerDelegate> delegate;
... your existing stuff ...
#end
#protocol ThirdControllerDelegate <NSObject>
- (void)thirdControllerDidDoTheThing:(ThirdController *)thirdController;
#end
Instead of having the ThirdController pop itself, it should tell its delegate that the thing happened, like so:
[self.delegate thirdControllerDidDoTheThing:self];
You'll also want to define a delegate protocol for SecondController, in the same way, and you'll want to specify that SecondController can act as a delegate for a ThirdController:
#import "ThirdController.h"
#protocol SecondControllerDelegate;
#class SecondController : UIViewController <ThirdControllerDelegate>
#property (nonatomic, weak) id<SecondControllerDelegate> delegate;
... your existing stuff ...
#end
#protocol SecondControllerDelegate <NSObject>
- (void)secondControllerDidDoTheThing:(SecondController *)secondController;
#end
Notice the extra bit in there where we put <ThirdControllerDelegate> after the #class line.
Now we find the part of the SecondController that shows the ThirdController, and have it set the controller's delegate first:
- (void)showThirdControllerAnimated:(BOOL)animated
{
ThirdController *thirdController = [[ThirdController alloc] init];
thirdController.delegate = self;
[self.navigationController pushViewController:thirdController animated:animated];
}
When the SecondController gets the message from the ThirdController, it should pass it on to its delegate, like this:
- (void)thirdControllerDidDoTheThing:(ThirdController *)thirdController
{
[self.delegate secondControllerDidDoTheThing:self];
}
Finally we modify FirstController so that it can act as the delegate to the SecondController:
#import "SecondController."
#class FirstController : UIViewController <SecondControllerDelegate>
When we show the SecondController, we make the FirstController its delegate:
- (void)showSecondControllerAnimated:(BOOL)animated
{
SecondController *secondController = [[SecondController alloc] init];
secondController.delegate = self;
[self.navigationController pushViewController:secondController animated:animated];
}
Finally we implement the SecondController's delegate method to pop to the first controller, then show a new secondController.
- (void)secondControllerDidDoTheThing:(SecondController *)secondController
{
[self.navigationController popToViewController:self animated:NO];
[self showSecondControllerAnimated:NO];
}
Done.
You've since altered your question; in the case you now describe you can follow the steps above to make the SecondController the delegate of the ThirdController, but then inside thirdControllerDidDoTheThing you just reload the data of your SecondController's view; if it's a UITableView or UICollectionView you'd do that with the reloadData method.
you should refresh your table view every time it is going to be shown; otherwise, the old data would be cached.
In the controller that controls the table view:
- (void)viewWillAppear {
[tableView reloadData];
}
I'm trying to find a solution that allows me to get keydown events in a view controller.
I do not believe a view controller is part of the responder chain by default.
I would appreciate a sample of how to go about this. I have had trouble finding documentation I can understand on how to add the VC to the responder chain and get the events.
Thanks.
Miek
You can implement something like this:
-(void) globalKeyDown: (NSNotification *) notification
method in your controller class, and then just add the observer in awakeFromNib...or loadView method of your controller
- (void)awakeFromNib
{
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(globalKeyDown:)
name:#"my_keyEvent"
object:nil];
}
in your view class
-(void)keyDown:(NSEvent *)theEvent
{
[[NSNotificationCenter defaultCenter] postNotificationName:#"my_keyEvent"
object:theEvent
userInfo:#{#"sender":self}];
}
NSViewController doesn't have a default way to do this. However, you can achieve this through subclassing NSView. Here is the basic idea:
If you create a view subclass, you can set your view controller as a delegate and create a delegate method that handles events.
You can declare a delegate protocol at the start of your view header.
Import your view header in the view controller header. Declare the view controller as implementing the protocol.
In your view keyDown send the event to the delegate.
Another way is to post NSNotifications in your keyDown and observe and handle the notifications in your view controller. Other ways also exist.
NSView Subclass with Delegate method explained
Here is the delegation example with an NSView subclass which declares a protocol in its header with one required method, an IBOutlet id property that conforms to the protocol. The NSView subclass calls this method to its delegate whenever it wants to. If the delegate is nil, that's fine in Cocoa. Also note, tangentially, I have added IB_Designable and IBInspectable to the view's color properties. This allows setting them in IB and requires the 10.10 SDK.
The app delegate has imported the NSView subclass in the AppDelegate.m implementation file and adopted the protocol in the AppDelegate class extension at the top of the .m file. In the #implementation section it also implements the method.
Also note in IB, I added an NSView to the window, then set its class to the custom NSView subclass in the inspector. Finally, I set its eventDelegate IBOutlet to the AppDelegate proxy in IB.
Custom NSView subclass interface
#import <Cocoa/Cocoa.h>
#protocol EventDelegatingViewDelegate <NSObject>
- (void)view:(NSView *)aView didHandleEvent:(NSEvent *)anEvent;
#end
IB_DESIGNABLE
#interface EventDelegatingView : NSView
#property IBOutlet id<EventDelegatingViewDelegate> eventDelegate;
#property IBInspectable NSColor *fillColor;
#property IBInspectable NSColor *strokeColor;
#end
Custom NSView subclass implementation
#import "EventDelegatingView.h"
#implementation EventDelegatingView
- (BOOL)acceptsFirstMouse:(NSEvent *)theEvent {return YES;}
// The following two methods allow a view to accept key input events. (literally they say, YES, please send me those events if I'm the center of attention.)
- (BOOL)acceptsFirstResponder {return YES;}
- (BOOL)canBecomeKeyView {return YES;}
- (void)drawRect:(NSRect)dirtyRect {
[super drawRect:dirtyRect];
[self.fillColor set];
NSRectFill(self.bounds);
[self.strokeColor set];
NSFrameRect(self.bounds);
}
// Notice these don't do anything but call the eventDelegate. I could do whatever here, but I didn't.
// The NICE thing about delgation is, the originating object stays in control of it sends to its delegate.
// However, true to the meaning of the word 'delegate', once you pass something to the delegate, you have delegated some decision making power to that delegate object and no longer have any control (if you did, you might have a bad code smell in terms of the delegation design pattern.)
- (void)mouseDown:(NSEvent *)theEvent
{
[self.eventDelegate view:self didHandleEvent:theEvent];
}
- (void)keyDown:(NSEvent *)theEvent
{
[self.eventDelegate view:self didHandleEvent:theEvent];
}
#end
App Delegate (and eventDelegate!) implementation
#import "AppDelegate.h"
// Import the view class and if there were other files that implement any protocol
#import "EventDelegatingView.h"
// Declare protocol conformance (or more accurately, not only import that protocol interface, but say you're going to implement it so the compiler can nag you if you don't)
#interface AppDelegate ()<EventDelegatingViewDelegate>
#property (weak) IBOutlet NSWindow *window;
// For the simplest demo app we don't even need this property.
#property IBOutlet EventDelegatingView *eventDelegatingView;
#end
#implementation AppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
// Insert code here to initialize your application
}
- (void)applicationWillTerminate:(NSNotification *)aNotification {
// Insert code here to tear down your application
}
// It's all right here. Receive a reference to a view and a reference to an event, then do as you like with them.
#pragma mark - EventDelegatingViewDelegate
- (void)view:(NSView *)aView didHandleEvent:(NSEvent *)anEvent
{
NSString *interestingEventNote;
switch (anEvent.type) {
case NSKeyDown:
case NSKeyUp:
{
// For simplicity we won't try to figure out the modifier keys here.
interestingEventNote = [NSString stringWithFormat:#"%# key was pressed.", anEvent.charactersIgnoringModifiers];
}
break;
case NSLeftMouseDown:
{
interestingEventNote = [NSString stringWithFormat:#"Left mouse down at point %# in window", NSStringFromPoint(anEvent.locationInWindow)];
}
break;
default:
break;
}
NSLog(#"%# %# aView=%#\n note=%#", self, NSStringFromSelector(_cmd), aView, interestingEventNote?interestingEventNote:#"Nothing worth noting");
}
#end
And that's it for the power of delegation. Basically it's callbacks of sorts and is a great way to build a class to enable it to defer something elsewhere as wanted. Moving some business logic to the right place in a fairly lazy and open and loosely coupled way.
NOTE: My code example shows using the app delegate. But the principal is the same. A view controller is little more than a delegate and you can add as much or as little as you like.
In your NSWidow (or NSWindowController) class implementation set your view controller as the first responder:
[self makeFirstResponder:yourViewControllerInstance];
You must, of course, make your NSViewController class return YES to the acceptsFirstResponder message.
I work on a project for iPad with Xcode 4.
I have a main view controller with many UITextField.
The TextFieldDelegate is a separate class in a separate file.
How can I refer, from TextFieldDelegate to a property (to a UITextField) of the main view controller (for example assign a value to a double)?
Thank you.
In most cases, if you want to use a separate delegate you should not need more information than what is passed to the delegate (the method's parameters). However, if you don't want to use your MainViewController as a delegate for your UITextField, you can initialize your TextFieldDelegate in your MainViewController instance and pass it the MainViewController instance.
For example you could have:
#import "MainViewController.h"
#interface TextFieldDelegate<UITextFieldDelegate> {
MainViewController* mainViewController;
}
#property(nonatomic,retain) MainViewController* mainViewController;
-(id)initWithController:(MainViewController*)controller;
#end
#implementation TextFieldDelegate
#synthesize mainViewController;
-(id)initWithController:(MainViewController*)controller {
if(self = [super init]) {
//some stuff
self.mainViewController = controller;
}
return self;
}
#end
Then in your MainViewController:
TextFieldDelegate tfd = [[TextFieldDelegate alloc] initWithController:self];
You just need to set the TextFields' delegate to tfd and you should be able to reference the MainViewController properties from the TextFieldDelegate instance. It's also possible to initiate it somewhere else, as long as you send the MainViewController instance to your TextFieldDelegate instance.
Edit: woups forgot a few '*'
So I have an app, and in the app there is a tableView, I have a uinavigationbarbutton that presents a modal viewController. When the user hits a go button in the modal interface, I want it dismiss the modal view and get some of the information in the modal view. I will than put that info in the tableView. To do this, I wrote a custom delegate, but it doesn’t work. I included my code below. Thanks for any help.
TrackerMainViewController.h //the tableView
#import "NewItemViewController.h"
#interface TrackerMainViewController : UITableViewController <UITableViewDelegate, DetailDelegate>
TrackerMainViewController.m
-(void)finishedAddingFoodItemFromDetail:(NSDate *)date whatWasEaten:(NSString *)whatFood whichMeal:(NSString *)meal {
NSLog(#"in delegate method here");
[self.tableView reloadData];
[self dismissModalViewControllerAnimated:YES];
}
NewItemViewController.h // the modal view
#protocol DetailDelegate <NSObject>
-(void)finishedAddingFoodItemFromDetail:(NSDate *)date whatWasEaten:(NSString *)whatFood whichMeal:(NSString *)meal;
#end
#interface NewItemViewController : UIViewController {
id <DetailDelegate> _delegate;
}
#property (nonatomic, retain) id <DetailDelegate> delegate;
#end
NewItemViewController.h
#implementation NewItemViewController
#synthesize delegate = _delegate;
//the go button in the modal view
- (IBAction)Go:(id)sender {
[self.delegate finishedAddingFoodItemFromDetail:[NSDate date] whatWasEaten:#"chicken" whichMeal:#"breakfast"];
}
I put a log in both the go button and in the implementation of the delegate in the tableview, but only the go log is being called.
Thanks
In the code you posted, you dont set the delegate. You need to set it similar to this detailView.delegate = self, otherwise it is nil. You can send messages to a nil-object without any warning and error, nothing will happen.