I'm teaching myself cocoa and enjoying the experience most of the time. I have been struggling all day with a simple problem that google has let me down on. I have read the Cocoa Bindings Program Topics and think I grok it but still can't solve my issue.
I have a very simple class called MTSong that has various properties. I have used #synthesize to create getter/setters and can use KVC to change properties. i.e in my app controller the following works:
mySong = [[MTSong alloc]init];
[mySong setValue:#"2" forKey:#"version"];
In case I am doing something noddy in my class code MTSong.h is:
#import <Foundation/Foundation.h>
#interface MTSong : NSObject {
NSNumber *version;
NSString *name;
}
#property(readwrite, assign) NSNumber *version;
#property(readwrite, assign) NSString *name;
#end
and MTSong.m is:
#import "MTSong.h"
#implementation MTSong
- (id)init
{
[super init];
return self;
}
- (void)dealloc
{
[super dealloc];
}
#synthesize version;
#synthesize name;
#end
In Interface Builder I have a label (NSTextField) that I want to update whenever I use KVC to change the version of the song. I do the following:
Drag NSObjectController object into the doc window and in the Inspector->Attributes I set:
Mode: Class
Class Name: MTSong
Add a key called version and another called name
Go to Inspector->Bindings->Controller Content
Bind To: File's Owner (Not sure this is right...)
Model Key Path: version
Select the cell of the label and go to Inspector
Bind to: Object Controller
Controller Key: mySong
Model Key Path: version
I have attempted changing the Model Key Path in step 2 to "mySong" which makes more sense but the compiler complains. Any suggestions would be greatly appreciated.
Scott
Update Post Comments
I wasn't exposing mySong property so have changed my AppController.h to be:
#import <Cocoa/Cocoa.h>
#class MTSong;
#interface AppController : NSObject {
IBOutlet NSButton *start;
IBOutlet NSTextField *tf;
MTSong *mySong;
}
-(IBAction)convertFile:(id)sender;
#end
I suspect File's owner was wrong as I am not using a document based application and I need to bind to the AppController, so step 2 is now:
Go to Inspector->Bindings->Controller Content
Bind To: App Controller
Model Key Path: mySong
I needed to change 3. to
Select the cell of the label and go to Inspector
Bind to: Object Controller
Controller Key: selection
Model Key Path: version
All compiles and is playing nice!
You want to bind the controller's content to the mySong key path as you suggested. What you are perhaps not doing is exposing mySong as a property or instance method in the File's Owner (typically your application delegate).
Related
I have a main window with a couple of popupbuttons. I want to clear them, then load the lists from a method in a custom class. I've got my view controller working and I know the method in the custom class (newRequest) is working because I added a NSLog command to print "Test" when the method executes. In AppDelegate I'm calling the method via:
[polyAppRequest newRequest];.
As I said, I know the method is executing. Why can't I removeallitems from the popupbutton from this custom class method?
Thanks
Keith
I read that you should use an NSWindowController to manage a window. See here:
Windows and window controllers
Adding views or windows to MainWindow
Then if your window gets complicated enough, the NSWindowController can employ various NSViewControllers to manage parts of the window.
In any case, I used an NSWindowController in my answer.
The image below shows the outlet's for File's Owner, which is my MainWindowController:
I created MainWindowController .h/.m in Xcode6.2 by:
Selecting File>New>File>OS X - Source - Cocoa Class
Selecting NSWindowController for Subclass of:
Checking also create .xib file for user interface
Then I deleted the window--not the menu--in the default MainMenu.xib, and I changed the name of MainWindowController.xib, created by the steps above, to MainWindow.xib.
The following code works for me (but I'm a Cocoa beginner!):
//
// AppDelegate.m
// PopUpButtons
#import "AppDelegate.h"
#import "MainWindowController.h"
#interface AppDelegate ()
#property(strong) MainWindowController* mainWindowCtrl;
#end
#implementation AppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
// Insert code here to initialize your application
[self setMainWindowCtrl:[[MainWindowController alloc] init]];
[[self mainWindowCtrl] showWindow:nil];
}
- (void)applicationWillTerminate:(NSNotification *)aNotification {
// Insert code here to tear down your application
}
#end
...
//
// MainWindowController.m
// PopUpButtons
//
#import "MainWindowController.h"
#import "MyData.h"
#interface MainWindowController ()
#property(strong) MyData* data;
#property(weak) IBOutlet NSPopUpButton* namePopUp;
#property(weak) IBOutlet NSPopUpButton* agePopUp;
#end
#implementation MainWindowController
-(id)init {
if (self = [super initWithWindowNibName:#"MainWindow"]) {
_data = [[MyData alloc] init]; //Get data for popups
}
return self;
}
- (void)windowDidLoad {
[super windowDidLoad];
// Implement this method to handle any initialization after your window controller's window has been loaded from its nib file.
[[self namePopUp] removeAllItems];
[[self namePopUp] addItemsWithTitles:[[self data] drinks]];
[[self agePopUp] removeAllItems];
[[self agePopUp] addItemsWithTitles:[[self data] extras]];
}
#end
...
//
// MyData.h
// PopUpButtons
//
#import <Foundation/Foundation.h>
#interface MyData : NSObject
#property NSArray* drinks;
#property NSArray* extras;
#end
...
//
// MyData.m
// PopUpButtons
//
#import "MyData.h"
#implementation MyData
- (id)init {
if (self = [super init]) {
_drinks = #[#"coffee", #"tea"];
_extras = #[#"milk", #"sugar", #"honey"];
}
return self;
}
#end
I hope that helps. If you need any more screenshots, let me know.
Edit1:
I think I see what you are asking about. Although I don't think it is a very good approach, if I change my code to this:
//
// MyData.h
// PopUpButtons
//
#import <Cocoa/Cocoa.h>
#interface MyData : NSObject
#property (copy) NSArray* drinks;
#property (copy) NSArray* extras;
-(void)newRequest;
#end
...
//
// MyData.m
// PopUpButtons
//
#import "MyData.h"
#interface MyData()
#property (weak) IBOutlet NSPopUpButton* drinksPopUp;
#property (weak) IBOutlet NSPopUpButton* extrasPopUp;
#end
#implementation MyData
- (id)init {
if (self = [super init]) {
_drinks = #[#"coffee", #"tea"];
_extras = #[#"milk", #"sugar", #"honey"];
}
return self;
}
-(void)newRequest {
[[self drinksPopUp] removeAllItems];
[[self drinksPopUp] addItemsWithTitles:[self drinks]];
[[self extrasPopUp] removeAllItems];
[[self extrasPopUp] addItemsWithTitles:[self extras]];
}
#end
I am unable to populate the NSPopUpButtons. This is what I did:
I dragged an Object from the Object Library to the dock in IB, and in the Identity Inspector, I changed the Object's class to MyData.
Then I clicked on the Connections Inspector, and the two instance variables in MyData, drinksPopUp and extrasPopUp, were listed in the Outlets.
I dragged from the outlets to the respective NSPopUpButtons.
I guess I assumed, like you, that when my program ran, the NSPopUpButtons would be assigned to the instance variables drinksPopUp and extrasPopUp--but that doesn't seem to be the case. According to the Apple docs, you should be able to do that:
An application typically sets outlet connections between its custom
controller objects and objects on the user interface, but they can be
made between any objects that can be represented as instances in
Interface Builder,...
Edit2:
I am able to pass the NSPopUpButtons from my MainWindowController to the newRequest method, and I can use the NSPopUpButtons inside newRequest to successfully populate the data.
Edit3:
I know the method in the custom class (newRequest) is working because
I added a NSLog command to print "Test" when the method executes.
But what happens when you log the variables that point to the NSPopUpButtons? With my code in Edit1, I get NULL for the variables, which means the NSPopUpButtons never got assigned to the variables.
Edit4:
If I add an awakeFromNib method to MyData, and inside awakeFromNib I log the NSPopUpButton variables for the code in Edit1, I get non NULL values. That tells me that the MainWindowController's windowDidLoad method is executing before MyData's awakeFromNib method, and therefore you cannot call newRequest inside MainWindowController's windowDidLoad method because MyData has not been fully initialized.
Edit5:
Okay, I got the code in Edit1 to work. The Apple docs say this:
About the Top-Level Objects
When your program loads a nib file, Cocoa recreates the entire graph
of objects you created in Xcode. This object graph includes all of the
windows, views, controls, cells, menus, and custom objects found in
the nib file. The top-level objects are the subset of these objects
that do not have a parent object [in IB]. The top-level objects typically
include only the windows, menubars, and custom controller objects that
you add to the nib file [like the MyData Object]. (Objects such as File’s Owner, First
Responder, and Application are placeholder objects and not considered
top-level objects.)
Typically, you use outlets in the File’s Owner object to store
references to the top-level objects of a nib file. If you do not use
outlets, however, you can retrieve the top-level objects from the
nib-loading routines directly. You should always keep a pointer to
these objects somewhere because your application is responsible for
releasing them when it is done using them. For more information about
the nib object behavior at load time, see Managing the Lifetimes of
Objects from Nib Files.
In accordance with the bolded line above, I changed this declaration in MainWindowController.m:
#interface MainWindowController ()
#property(strong) MyData* data;
...
#end
to this:
#interface MainWindowController ()
#property(strong) IBOutlet MyData* data;
...
#end
Then, in IB I dragged a connection from the MainWindowController data outlet to the MyData Object(the Object I had previously dragged out of the Object Library and onto the doc).
I guess that causes MyData to unarchive from the .xib file and initialize before MainWindowController.
I have a Model Class like this:
Header:
#interface RTSecurityModel : NSObject
{
NSString *code;
}
#property NSString *code;
#end
Implementation:
#implementation RTSecurityModel
#synthesize code;
#end
Then I have my App Delegate:
Header:
#interface RTAppDelegate : NSObject <NSApplicationDelegate>
{
RTSecurityModel *security;
}
#property (assign) IBOutlet NSWindow *window;
#property RTSecurityModel *security;
#end
Implementation:
#implementation RTAppDelegate
#synthesize security;
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
security = [[RTSecurityModel alloc] init];
security.code = #"test";
}
Then in my MainMenu.xib I've create a label and in the Bindings Inspector set "Bind To: App Delegate" with "Model Key Path: security.code".
But nothing is showing when I'm starting my application.
I tried soooo many ways to bind this variable, but no one gave success.
Please help me not to hate XCode and Cocoa!
UPD: http://www.experts-exchange.com/Programming/Languages/C/A_3381-Simple-Binding-Cocoa-GUI-Application-without-Outlets.html
Here is the sample how to set Property and Label value by editing the Text Field
But is there a way to edit Label without editing the Text Field? Or without Text Field at all?
UPD2:
You must not create another instance of Object
security = [[RTSecurityModel alloc] init]; // Kill this
Many many thanks to Viktor Lexington
Instead of using security.code as the model path use code. Use the class RTSecurityModel in the value section of the bindings tab instead of the AppDelegate.
Here is a demo project.
Do not bind the Text Field Cell, use the Text Field.
You can check if a value is null if you fill the Null Placeholder with text, will it show that text instead? Then in time of binding the value it null.
To see your RTSecurityModel in the Interface Builder you must let it know your class, it won't look for it.
Add an Object and then set the custom class of it to RTSecurityModel.
Then you can choose this object and set the referencing outlet to the property in the App Delegate.
Assignment will now be directly reflected in the label.
I can think of two ways to solve this programmatically without Interface Builder:
Key Value Coding
// add an observer for the value on the object that has the method below implemented
[self addObserver: self forKeyPath: #"security.code" options: NSKeyValueObservingOptionNew context: NULL];
// method will be called when the observer has 'seen' a value change
-(void) observeValueForKeyPath: (NSString *)keyPath ofObject: (id) object change: (NSDictionary *) change context: (void *) context {
label.text = ...
}
Use a custom setter for code (#synthesize will still create the getter for you)
- (void)setCode:(NSString *)aString {
label.text = aString;
}
another question i'm trying to use a setter within another class but I seem to get this odd error here is the code below:
AppDataSorting.h
#import <Foundation/Foundation.h>
#interface AppDataSorting : NSObject{
NSString *createNewFood;
NSNumber *createNewFoodCarbCount;
}
#property (readwrite) NSString *createNewFood;
#end
AppDelegate.m
#import "AppDelegate.h"
#implementation AppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
// Insert code here to initialize your application
}
- (IBAction)saveData:(id)sender {
NSLog(#"%#", self.foodName.stringValue);
self.createNewFood = self.foodName.stringValue;
NSLog(#"%.1f", self.carbAmount.floatValue);
}
#end
I get the error message in AppDelegate.m which is: Property 'createNewFood' not found on object of type 'AppDelegate *'
Could someone please explain the issue here?
You declare this property:
#property (readwrite) NSString *createNewFood;
In AppDataSorting.h so you can access it like self.createNewFood in AppDataSorting.m file not AppDelegate.m. If you want to call it as you do in AppDelegate.m you have move this line:
#property (readwrite) NSString *createNewFood;
to AppDelegate.h file.
Or if you want to use property from AppDataSorting class in AppDelegate you have to create object and call it on that object:
- (IBAction)saveData:(id)sender {
NSLog(#"%#", self.foodName.stringValue);
AppDataSorting *dSorting = [[AppDataSorting alloc] init];
dSorting.createNewFood = self.foodName.stringValue;
NSLog(#"%.1f", self.carbAmount.floatValue);
}
In -saveData:, self refers to an instance of NSAppDelegate. The createNewFood property is defined on instances of the class AppDataSorting.
Also note that Cocoa/CF naming conventions give special meaning to methods that start with "init", "new" and (to a lesser degree) "create". You probably want to avoid such things in your property names. Details here.
In general, properties should represent conceptual "properties" of an object. So if you had a Person class, it might have a name property, but it wouldn't have a createNewOutfit property.
You need to access createNewFood on an instance of AppDataSorting - but you're trying to access the property on the AppDelegate-class which clearly doesn't implement it.
So you would need to create an instance of AppDataSorting and then access the property like so:
AppDataSorting *instance = [[AppDataSorting alloc] init];
instance.createNewFood = self.foodName.stringValue;
Final notes:
The docs provide a good base of information
If you don't need atomicity you should always declare properties with the nonatomic attribute
createNewFood is not a good name for a property since it suggests a method which creates new food - yet it's only meant to store data (in this case an NSString instance)
The bulk of the code for my app is in a 'm' file called MyViewController. The app implements a custom UIView which contains a UIWebView object. The code for the UIView and UIWebView is kept in a separate 'm' file called CustomUIView.
I have managed to override clicks on URL hyperlinks in the UIWebView object using a delegate. However, I would like to have these clicks launch a method that is stored in my main app code. This method is called "popupView", and takes a single argument, "inputArgument". The inputArgument is the text of the URL the user clicks on. In fact, this method is the very same one that causes my custom UIView to launch.
Anyway, what I'd like to do is have my overridden URL clicks cause the popupView method to launch, thus causing another UIView to open on top of the one that was clicked on.
The problem is that the 'm' file where the URL clicks are detected can't see the 'popupView' method as it is included in the MyViewController 'm' file. How do I call the popupView method from another 'm' file?
Directly
Declare MyViewController's method -popupView: in MyViewController.h.
#import MyViewController.h in CustomUIView.m.
Give CustomUIView a reference to the [one] instance of MyViewController, for example by way of an #property declared in CustomUIView.h.
For (1), the #interface of MyViewController (in MyViewController.h) should look a bit like this
#interface MyViewController : UIViewController
{
//....
}
- (void)popupView:(NSString *)urlText;
//....
#end
For (2), UIViewController.m should have the following somewhere near the top
#import "CustomUIView.h"
#import "MyViewController.h"
For (3), the #interface in CustomUIView.h should look something like
#interface CustomUIView : UIView
{
//....
}
#property (nonatomic, weak) MyViewController *viewController;
#end
This property will need to be set some time after the instance of CustomUIView owned by MyViewController is created. If your CustomUIView is in MyViewController.xib, you can set this property on it by adding the keyword IBOutlet to the property's declaration like this
#property (nonatomic, weak) IBOutlet MyViewController *viewController;
and pointing this property to "File's Owner" in the XIB. If instead, you create the CustomUIView programmatically, you can set this property on it as soon as you have initialized it.
Delegate
This, however, is far from being a best practice. It would be much better to make use of the delegate pattern. To do this, you'll need to
Define a delegate protocol.
Add a "delegate" #property to CustomUIView.
Call the delegate methods on the delegate object at the appropriate times.
Implement the protocol in MyViewController.
Set the "delegate" #property of the instance of CustomUIView owned by the MyViewController instance to be the MyViewController instance.
Let's call our delegate protocol something imaginative like CustomUIViewDelegate. For (1), we'll declare it at the top of CustomUIView.h as follows:
#class CustomUIView;
#protocol CustomUIViewDelegate <NSObject>
- (void)customUIView:(CustomUIView *)customView didSelectURLText:(NSString *)urlText;
#end
Notice that we've had to forward declare our class CustomUIView so that the compiler is able to make sense of the type of the first argument in the protocol method customUIView:didSelectURLText:.
For (2), we'll do something quite similar to (3) above: Your CustomUIView #interface will look something like
#interface CustomUIView : UIView
{
//....
}
#property (nonatomic, weak) id<CustomUIViewDelegate> *delegate;
#end
Again, if we're going to set this property in Interface Builder, we'll need to use the IBOutlet keyword to announce it to IB:
#property (nonatomic, weak) IBOutlet id<CustomUIViewDelegate> *delegate;
For (3), we need to call the delegate method customUIView:didSelectURLText: on our delegate object self.delegate at the appropriate time.
In your question, you wrote
I have managed to override clicks on URL hyperlinks in the UIWebView object using a delegate.
So, let's say that CustomUIView has an instance method
- (void)didSelectURL:(NSURL *)url
{
//....
}
which you call when the user selects a link in the UIWebView. The CustomUIView's delegate needs to be informed of this:
- (void)didSelectURL:(NSURL *)url
{
//...
if ([self.delegate respondsToSelector:#selector(customUIView:didSelectURLText:)]) {
{
[self.delegate customUIView:self didSelectURLText:url.absoluteString];
}
}
Notice that we check first whether the CustomUIView instance's delegate object implements the selector of interest (customUIView:didSelectURLText:) by calling respondsToSelector: on it.
For (4), we'll need first to add <CustomUIViewDelegate> to MyViewController's #interface declaration and be sure to #import CustomUIView.h into the file where we use the symbol CustomUIViewDelegate. Our MyViewController's #interface will look something like this:
#import "CustomUIView.h"
#interface MyViewController : UIViewController <CustomUIViewDelegate>
{
//....
}
//....
#end
More importantly, we need to implement the CustomUIViewDelegate protocol in MyViewController's #implementation; so far we've only declared that MyViewController adopts it.
To do this, since our protocol consists of only one method, we'll need only to add our own implementation of -customUIView:didSelectURLText:. Our MyViewController's #implementation will look something like this:
#import "MyViewController.h"
#implementation MyViewController
//....
- (void)popupView:(NSString *)urlText
{
//....
}
#pragma mark - CustomUIViewDelegate
- (void)customUIView:(CustomUIView *)customView didSelectURLText:(NSString *)urlText
{
[self popupView:urlText];
}
//....
#end
Finally, for (5), we'll need to set the delegate property of the instance of CustomUIView owned by the MyViewController instance. I don't know enough about MyViewController's relationship with its CustomUIView instance to do describe how to do this definitively, but I'll provide an example: I'll assume that you programmatically, in -[MyViewController loadView] add the CustomUIView as a subview of MyViewController's view. So your implementation of -loadView looks a bit like this:
- (void)loadView
{
[super loadView];
//....
CustomUIView *customView = //....
//....
[self.view addSubview:customView];
//....
}
All that remains to do at this point is to set the delegate #property of the local variable customView to self:
customView.delegate = self;
Edit: Updated (5) in light of new information about the relationship between CustomUIView and MyViewController.
In your comment, you write that your CustomUIView is added as a subview of cvc.view where cvc is an instance of CustomUIViewController in CustomUIView's method -[CustomUIView show]. On account of this, you note that writing customView.delegate = self; is the same as writing self.delegate = self, which is clearly not what you want to do.
You want to set the CustomUIView's delegate property to be the instance of MyViewController. Consequently, your method -[CustomUIView show] should look something like
- (void)show
{
//....
[cvc.view addSubview:self];
self.delegate = mvc;
}
where mvc is the instance of MyViewController.
Well, since you are writing the CustomUIView, why not implement a constructor like initWithPopupDelegate:(MyViewController *)delegate and keep a reference to the MyViewController instance that way in an instance variable, then call the method on that.
(Add #class MyViewController; at the top CustomUIView.h, and #import "MyViewController.h" at the top of CustomUIView.m so the compiler knows the class you are using.)
Alternatively, if there is ever only one MyViewController instance, you can define a class method for MyViewController, e.g., + (MyViewController *)instance, and have that return a reference to the one instance (which you store in a class variable and set the first time when you create the instance, see “singleton pattern”). But without knowing the specifics of your code, I would suggest the first solution (delegate) as simpler and more flexible.
this is a follow-up question to my last one here: iOS: Initialise object at start of application for all controllers to use .
I have set my application up as follows (ignore the DB Prefix):
DBFactoryClass // Built a DataManaging Object for later use in the app
DBDataModel // Is created by the factory, holds all data & access methods
DBViewControllerA // Will show some of the data that DBDataModel holds
moreViewControllers that will need access to the same DBDataModel Object
i will go step by step through the application, and then post the problem in the end
AppDelegate.h
#import "DBFactoryClass.h"
AppDelegate.m
- (BOOL)...didFinishLaunching...
{
DBFactoryClass *FACTORY = [[DBFactoryClass alloc ]init ];
return YES;
}
DBFactoryClass.h
#import <Foundation/Foundation.h>
#import "DBDataModel.h"
#interface DBFactoryClass : NSObject
#property (strong) DBDataModel *DATAMODEL;
#end
DBFactoryClass.m
#import "DBFactoryClass.h"
#implementation DBFactoryClass
#synthesize DATAMODEL;
-(id)init{
self = [super init];
[self setDATAMODEL:[[DBDataModel alloc]init ]];
return self;
}
#end
ViewControllerA.h
#import <UIKit/UIKit.h>
#import "DBDataModel.h"
#class DBDataModel;
#interface todayViewController : UIViewController
#property (strong)DBDataModel *DATAMODEL;
#property (weak, nonatomic) IBOutlet UILabel *testLabel;
#end
ViewControllerA.m
#import "todayViewController.h"
#implementation todayViewController
#synthesize testLabel;
#synthesize DATAMODEL;
- (void)viewDidLoad
{
todaySpentLabel.text = [[DATAMODEL test]stringValue]; // read testdata
}
#end
DBDataModel.h
#import <Foundation/Foundation.h>
#interface DBDataModel : NSObject
#property (nonatomic, retain) NSNumber* test;
#end
DBDataModel.m
#import "DBDataModel.h"
#implementation DBDataModel
#synthesize test;
-(id)init{
test = [[NSNumber alloc]initWithInt:4]; // only a testvalue
return self;
}
#end
the app builds fine, and starts up but the label stays blank. so either the object does not exist (but i guess this would result in an error message), or something else is wrong with my setup. any thoughts?
Two notes:
Your have a shotgun approach to asking questions: everytime you hit a stumbling block, you ask a question and if the answer does not work immediately, you ask another one. You have to spend some energy in between the questions debugging and poking into the code on your own, otherwise you will depend on the external help forever.
Use the common coding style please. CAPS are reserved for macros.
Now to the code:
- (BOOL) …didFinishLaunching…
{
DBFactoryClass *factory = [[DBFactoryClass alloc] init];
return YES;
}
This simply creates an instance of the DBFactoryClass and then throws it away. In other words, it’s essentially a no-op. Judging by the comments in the previous answer you create the controllers using the Storyboard feature. How are they supposed to receive the reference to the data model? The reference isn’t going to show up by magic, you have to assign it somewhere.
I’m not familiar with the Storyboard feature. The way I would do it is to create the view controllers using separate XIB files, then you can create the controller instances in the Factory class and pass them the needed reference to the model. In the end the application delegate would create the factory, ask it to assemble the main controller and then set it as the root view controller for the window. Just like in my sample project. It’s possible that there’s a way to make it work with storyboards, but as I said, I am not familiar with them.