I am a newbie learning "iPad and iPhone Application Development" course. In the demo of lecture 5, we have some code like this
#import "HappinessViewController.h"
#import "FaceView.h"
#interface HappinessViewController ()
#property (nonatomic, weak) IBOutlet FaceView *faceView;
#end
#implementation HappinessViewController
#synthesize happiness = _happiness;
#synthesize faceView = _faceView;
-(void) setHappiness:(int)happiness
{
_happiness = happiness;
[self.faceView setNeedsDisplay];
}
-(void)setFaceView:(FaceView *)faceView
{
_faceView = faceView;
NSLog(#"set FaceView invoked");
[self.faceView addGestureRecognizer:[[UIPinchGestureRecognizer alloc]
initWithTarget:self.faceView action:#selector(pinch:)]];
}
-(BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
{
return YES;
}
#end
in method "-(void)setFaceView:(FaceView *)faceView", I wonder it might be something similar to event listener in javascript. But I also want to know
when the event listener was bound. So I add "NSLog(#"set FaceView invoked");". It turns out that this setter function was invoked once I run this program which makes me really very confused. So I am wondering how "setFaceView" is invoked at the very beginning?
By the way, FaceView is a subclass of UIView and faceView is the only instance of FaceView class. And also I try to add "NSLog(#"set happiness invoked");" in method setHappiness, this
is not invoked at the very beginning of program.
If you have faceView bound to a view in a NIB or a Storyboard, then -setFaceView: is called when the NIB is loaded or the view controller is loaded by the Storyboard.
-setFaceView: is the setter for the faceView property. Whenever self.faceView = … is done, it's -setFaceView: that gets called.
Related
I have the following protocol:
#protocol CardTransferFundsDelegate <NSObject>
#property (strong, nonatomic) id<CardTransferFundsView> view;
#end
I have the following in the .h file:
#interface CardTopViewModel : NSObject<CardTransferFundsDelegate>
- (instancetype)initWithVirtualCard:(Card *)card;
#end
In my .m I have the following:
#interface CardTopUpViewModel()
#property (strong, nonatomic) Card *card;
#end
#implementation CardTopUpViewModel
-(instancetype)initWithCard:(Card *)card {
self = [super init];
if(self){
self.card = card;
}
return self;
}
- (id <CardTransferFundsView>)view {
return nil;
}
- (void)setView:(id <CardTransferFundsView>)view {
self.view = view;
}
#end
The issue I have is whenever I call setView it then calls self.view which then calls the getter method and I have a program that just keeps running infinitely.
So my question is, How do I fix this issue, such that the protocol still keeps the property but I am able to get and set the view without having the program run infinitely?
You have implemented the setter, setView, in terms of itself, set.view, so it will recurse until the call stack overflows.
To implement the property specified in your protocol you need three things:
Storage - an instance variable in which to hold the properties value
A setter
A getter
First add an instance variable, say myView:
#implementation CardTopUpViewModel
{
id <CardTransferFundsView>) myView; // storage for view property
}
Now your setter becomes:
- (void)setView:(id <CardTransferFundsView>)view
{
myView = view;
}
And the getter is similarly trivial.
Or of course you can just skip all this and use a property declaration in your #interface which matches that in the protocol and the compiler will provide the storage, setter and getter automagically.
HTH
You should not call self.view = view will call the setter method again and again resulting infinite call. That moto is do not call setter method in with in setter method (setting property will call it again). So Issue in below lines. so view is already a property of viewcontroller. - (void) setView:(id)view is setter method for the view Property. try use another name.
Basically you should be very careful while creating method start with set. Usually try to use method name which starts with any verb as it does some action.
- (void)setView:(id <CardTransferFundsView>)view {
self.view = view;
}
create any property of id <CardTransferFundsView>) with other name and use with in setter method in place of self.view = view.
I have created a custom class "CustomSCNView" that inherits from SCNView. I want to use the custom class in another view controller. So I need to create a CustomSCNView object and use it to another class to manipulate things. But how can I create a CustomSCNView object in another class.
This is not working:
CustomSCNView *customView = [[CustomSCNView alloc]init]; //in viewcontroller.m
Sorry forgot to mention I used the interface builder to drag a SCNView to the view controller and then set its class to CustomSCNView.
I'm a bit confused by your question, but I've created a sample project at https://github.com/NSGod/CustomSCNView that may do what you're looking for.
First, the storyboard has 2 CustomSCNViews laid out side by side in the ViewController's view. Like you did, I dragged 2 SCNViews from the IB palette to the view and then set the custom class to be CustomSCNView.
Second, is the CustomSCNView class which is defined as follows:
#import <Cocoa/Cocoa.h>
#import <SceneKit/SceneKit.h>
#interface CustomSCNView : SCNView
#property (nonatomic, assign) BOOL allowsRotation;
#end
You can see, it has an allowsRotation property that any other object can set.
To set a default value for allowsRotation, other than NO, you can override initWithCoder: which is what's used when you set up the views in Interface Builder like you did:
#import "CustomSCNView.h"
#implementation CustomSCNView
- (id)initWithCoder:(NSCoder *)coder {
if ((self = [super initWithCoder:coder])) {
_allowsRotation = YES;
}
return self;
}
#end
The ViewController then has 2 IBOutlets to both CustomSCNViews.
#import <Cocoa/Cocoa.h>
#import <SceneKit/SceneKit.h>
#class CustomSCNView;
#interface ViewController : NSViewController
#property (weak) IBOutlet CustomSCNView *sView1;
#property (weak) IBOutlet CustomSCNView *sView2;
#end
ViewController.m:
#import "ViewController.h"
#import "CustomSCNView.h"
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
_sView1.allowsRotation = NO;
_sView2.allowsRotation = YES;
}
#end
You can see that in viewDidLoad, you can set the allowsRotation property of both views to whatever you want. When you run this application, 2 instances of CustomSCNView are created for you automatically (via initWithCoder:), when the storyboard/nib files are loaded. There's no need to create another instance of a CustomSCNView to be able to set the properties of the 2 existing instances you already have.
If you look at the documentation for SCNView it tells you:
You can create a SceneKit view by using its initWithFrame:options:
method or by adding it to a nib file or storyboard.
So you cannot use the init method unless you have implemented your [CustomSCNView init] method to call [super initWithFrame:options:].
If you need access to custom subclass properties from Interface Builder, mark those properties IBInspectable (and possibly implement IBDesignable). That's documented by Apple here, and nicely summarized on NSHipster.
In any initialization path, you must call the superclass's designated initializer. For SCNView, that appears to be initWithFrame:options: (not documented as such, but the header strongly implies it). See this document on multiple initializers and subclassing.
That said, though, subclassing SCNView is a code smell that you might be fighting the framework and working too hard.
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 ultimately want to write an iOS app incorporating ALAssetsLibrary, but as a first step toward understanding delegation, I'm trying to pass a simple message between two view controllers. For some reason, I can't seem to get the message to pass. In particular, the delegate object (derpy) doesn't appear to exist (if(self.derpy) returns NO)).
I asked the same question on the Apple forums and was told that I should be using segues and setting properties / calling methods using self.child instead, but that seems strange. If I were to pass messages using the parent / child properties, would I still be able to create my views in Interface Builder? Once I have my two views set up, say inside a UINavigationController, I'm not sure how to actually "wire them up" so I can pass messages between them. Sorry if the question is overly broad.
Here's the controller I'm declaring the protocol in (called PickerViewController):
Interface:
#import <UIKit/UIKit.h>
#import <AssetsLibrary/AssetsLibrary.h>
#protocol DerpDelegate <NSObject>
#required
- (void) test;
#end
#interface PickerViewController : UIViewController
#property (nonatomic, assign) id<DerpDelegate> derpy;
#end
Implementation:
#import "PickerViewController.h"
#interface PickerViewController ()
#end
#implementation PickerViewController
- (void)viewDidLoad
{
[super viewDidLoad];
if (self.derpy) { // If the delegate object exists
[self.derpy test]; // send it this message
} else {
NSLog(#"Still not working."); // This always returns (i.e., self.derpy doesn't exist)
}
}
Delegate controller (MainViewController) interface:
#import <UIKit/UIKit.h>
#import "PickerViewController.h"
#interface MainViewController : UIViewController <DerpDelegate> // public promise to implement delegate methods
#property (strong, nonatomic) PickerViewController *picker;
- (void) test;
#end
And lastly, the delegate controller (MainViewController) implementation:
#import "MainViewController.h"
#import "PickerViewController.h"
#interface MainViewController ()
#end
#implementation MainViewController
// Here's that method I promised I'd implement
- (void) test{
NSLog(#"Test worked."); // This never gets called
}
- (void)viewDidLoad {
[super viewDidLoad];
self.picker.derpy = self;
//lazy instantiation
- (PickerViewController *) picker{
if(!_picker) _picker = [[PickerViewController alloc]init];
return _picker;
}
EDIT: Many thanks to rydgaze for pointing me in the right direction with self.picker.derpy = self, but for some reason, things still aren't working properly. Importantly, once that property has been set, if(self.picker.derpy) returns YES from MainViewController. But if(self.derpy) is still returning NO when called from inside the PickerViewController's viewDidLoad. How can the property exist and not exist at the same time?
You need to be sure that you're setting the delegate on the instance of the view controller that you put on screen. If you're using a navigation controller and segues to go between MainViewController and PickerViewController, then you should set the delegate in prepareForSegue:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
self.picker = (PickerViewController *)segue.destinationViewController;
self.picker.derpy = self;
}
You need to populate the delegate first.
Basically, your MainViewController shoudl at somepoint do a
picker.derpy = self;
Then when the delegate fires in PickerViewController, the callback will happen.
Edit:
A good practice is to do something like in PickerViewController
#property (nonatomic, assign) id<DerpDelegate > derpy;
and in your MainViewController indicate that you will implement the delegate
#interface MainViewController : UIViewController<DerpDelegate>
Eventually in your implementation of MainViewController
You will have something like
picker = [[PickerViewController alloc]init];
picker.derpy = self;
[picker doYourThing];
Once picker is all done, it may want to return results using the delegate.
I´m having problems declarating my own delegate. Well...thats not exactly true: i have it declarated and, when i build the project, the compiler reports no issues. I declarated it in this way:
I made a file (enviarDatos.h) for declare the protocol:
#protocol enviarDatos <NSObject>
- (void)addItemViewController:(NSMutableArray *)item;
#end
In the Vista2.h (ViewController) file I imported the file enviarDatos.h and declared a property:
#property (nonatomic, weak) id <enviarDatos> delegare;
In the Vista2.m (ViewController) file I use the protocol method:
#interface ViewController : UIViewController <enviarDatos> {
And, finally, in the ViewController.m file I implement the delegates method:
- (void)addItemViewController:(NSMutableArray *)ar {
origen = ar;
}
Does anyone see something wrong? the code of the last function its never executing.
Thanks for your help.
EDIT:
What i need is to change an array in ViewController from Vista2 (another viewcontroller)
Then create delegate property in next view(child view) & set it to self in parent view while pushing or showing child view.
ParentView.m
1.Implement protocol methods
- (void)addItemViewController:(NSMutableArray *)ar
{
origen = ar;
}
2.While showing child view
ChildViewController *child = [[ChildViewController alloc] init];
child.delegate = self;
//present child view
ChildView.h
#property (nonatomic, weak) id <enviarDatos> delegare;
ChildView.m
-(void) anyMethod
{
if([self.delegate respondsToSelector:#selector(addItemViewController:)])
{
[self.delegate addItemViewController:mutableArray];
}
}
Ah, it looks like you are declaring the delegate property in the wrong place.
You should declare the property delegate in enviarDatos.h.
#property (nonatomic, weak) id <enviarDatos> delegate;
Then in Vista2.m you will do something like this...
EnviarDatos *myObject = [[EnviarDatos alloc] init];
myObject.delegate = self;
This then sets up the EnviarDatos object and assigns the Vista2 object as the delegate.
Now, in EnviarDatos.m you can run...
[self.delegate addItemViewController:someObjectArray];
And this will then run that code in the Vista2 object.
Delegates are used for calling back to objects that create them (or some other objects). If you create an object and then want to run a method in it then you won't need a delegate.
Can you say at what condition addItemViewController is invoked?
You seem to be on the right track, but are you sure you are setting the delegate as
[yourObject setDelegate: self];
Have you tried debugging it? Does the debugger pause at addItemViewController if you set a breakpoint there? Can you confirm the delegate is not null inside the method? I may post some code but your seems to be right except for the assigning of delegate, I think you should check it.