How does an NSView subclass communicate with the controller? - cocoa

I am brand spanking new to Cocoa programming, and am still kind of confused about how things wire together.
I need a pretty simple application that will fire off a single command (let's call it DoStuff) whenever any point on the window is clicked. After a bit of research it looks like subclassing NSView is the right way to go. My ClickerView.m file has this:
- (void)mouseDown:(NSEvent *)theEvent {
NSLog(#"mouse down");
}
And I have added the View to the Window and have it stretching across the whole thing, and is properly writing to the log every time the window is clicked.
I also have my doStuff method on my controller (this could be refactored to its own class I suppose, but for now it works):
- (IBAction)doStuff:(id)sender {
// do stuff here
}
So, how do I get mouseDown in ClickerView to be able to call DoStuff in the controller? I have a strong .NET background and with that, I'd just have a custom event in the ClickerView that the Controller would consume; I just don't know how to do that in Cocoa.
edit based on Joshua Nozzi's advice
I added an IBOutlet to my View (and changed it to subclass NSControl):
#interface ClickerView : NSControl {
IBOutlet BoothController *controller;
}
#end
I wired my controller to it by clicking and dragging from the controller item in the Outlets panel on the View to the controller. My mouseDown method now looks like:
- (void)mouseDown:(NSEvent *)theEvent {
NSLog(#"mouse down");
[controller start:self];
}
But the controller isn't instantiated, the debugger lists it as 0x0, and the message isn't sent.

You could either add it as an IBOutlet like Joshua said, or you could use the delegate pattern.
You would create a Protocol that describes your delegate's methods like
#protocol MyViewDelegate
- (void)doStuff:(NSEvent *)event;
#end
then you'd make your view controller conform to the MyViewDelegate protocol
#interface MyViewController: NSViewController <MyViewDelegate> {
// your other ivars etc would go here
}
#end
Then you need to provide the implementation of the doStuff: in the implementation of MyViewController:
- (void)doStuff:(NSEvent *)event
{
NSLog(#"Do stuff delegate was called");
}
then in your view you'd add a weak property for the delegate. The delegate should be weak, so that a retain loop doesn't form.
#interface MyView: NSView
#property (readwrite, weak) id<MyViewDelegate> delegate;
#end
and then in your view you'd have something like this
- (void)mouseDown:(NSEvent *)event
{
// Do whatever you need to do
// Check that the delegate has been set, and this it implements the doStuff: message
if (delegate && [delegate respondsToSelector:#selector(doStuff:)]) {
[delegate doStuff:event];
}
}
and finally :) whenever your view controller creates the view, you need to set the delegate
...
MyView *view = [viewController view];
[view setDelegate:viewController];
...
Now whenever your view is clicked, the delegate in your view controller should be called.

First, your view needs a reference to the controller. This can be a simple iVar set at runtime or an outlet (designated by IBOutlet) connected at design time.
Second, NSControl is a subclass of NSView, which provides the target/action mechanism machinery for free. Use that for target/action style controls. This provides a simple way of setting the reference to your controller (the target) and the method to call when fired (the action). Even if you don't use a cell, you can still use target/action easily (NSControl usually just forwards this stuff along to its instance of an NSCell subclass but doesn't have to).

you can also use a selector calling method,
define two properties in custom class:
#property id parent;
#property SEL selector;
set them in view controller:
graph.selector=#selector(onCalcRate:);
graph.parent=self;
and call as:
-(void)mouseDown:(NSEvent *)theEvent {
[super mouseDown:theEvent];
[_parent performSelector:_selector withObject:self];
}

Related

How to create a reusable button

I'm new to Xcode and objective c. I want to create a button (probably a UIBarButtonItem, for a navigation bar) with a particular appearance, which I will use repeatedly in different views. I've searched at length but can't figure out how.
Would it be appropriate to subclass UIBarButtonItem? I tried to do that, but I was quickly in over my head. Once I create the .h and .m files as a subclass of UIBarButtonItem, do I then have to instantiate a UIBarButtonItem? Do those files not automatically create a button object for me (imported from the parent class), which I can refer to as self? It seems like it would be weird to instantiate a button within its own subclass.
One thing I want to do is add the line,
button.titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
but I'm at a loss as to how to create reusable button with that property.
Even if that is completely the wrong approach to creating a reusable custom button, I clearly need to improve my understanding of objects, so explanation of my misunderstandings would be much appreciated!
Please?
You can do this without subclassing - by making a category (a preferred way of doing things in Objective-C). With a category you can provide custom methods for an object without having to subclass it. You can't (easily) provide custom properties, but in your case this is not relevant.
Using a Category
This is how your category header file could look:
// UIButton+StyledButton.h
#import <UIKit/UIKit.h>
#interface UIButton (StyledButton)
- (void) styleButton;
#end
Then in the implementation file:
//
// UIButton+StyledButton.m
//
#import "UIButton+StyledButton.h"
#implementation UIButton (StyledButton)
- (void) styleButton {
//style your button properties here
self.titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
}
('self' refers to the button object, which also acquires the custom methods you write in the category.)
To use it, #import "UIButton+StyledButton.h" then you can do this sort of thing...
on viewDidLoad {
[super viewDidLoad];
UIButton* myButton = [[UIButton alloc] initWithFrame:myFrame];
[myButton styleButton];
}
Using a Subclass
The subclassed equivalent would look something like this:
The header file...
// MyCustomButton.h
#import <UIKit/UIKit.h>
#interface MyCustomButton : UIButton
- (id)initWithCoder:(NSCoder *)coder;
- (id)initWithFrame:(CGRect)frame;
#end
The implementation file...
// MyCustomButton.m
#import "MyCustomButton.h"
#implementation MyCustomButton
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self styleButton];
}
return self;
}
- (id)initWithCoder:(NSCoder *)coder
{
self = [super initWithCoder:coder];
if (self) {
[self styleButton];
}
return self;
}
- (void) styleButton {
//style your button properties here
self.titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
}
You provide two init methods - initWithFrame is the method to call when alloc/initing the object in code; initWithCoder is the init method called by the system if loading the object from a storyboard or xib.
To create one of your custom buttons in code, you alloc/init as you would any other object:
MyCustomButton* button = [[MyCustomButton alloc] initWithFrame:buttonFrame];
You wouldn't also alloc/init the superclass instance, this is done by the initWithFrame: method in the subclass when it calls [super initWithFrame:frame]. self refers to your custom subclass instance, but that includes all of the (public) properties and methods from it's superclass - unless you have implemented overrides in the subclass.
To use your subclassed button in a storyboard/xib, just drag out a regular button then set it's type to your custom button class in the Identity Inspector. The initWithCoder method is called automatically when the button is loaded from the storyboard/xib into a view.
update
From your comments, you seem to harbour a few confusions still, so here are some highly compressed de-obfuscating notes...
Keep away from subclassing UINavigationController unless you really know what you are doing. It's rarely necessary.
The buttons on a navController's interface are properties of it's contained viewControllers. Look up the navigationItem property of UIViewController (similarly - in the case of a UIToolbar - the View Controller has a toolbarItems property). This allows Navigation Controllers to be context-aware.
The 'viewDidLoad' in my example is assumed to be in a regular UIViewController. My example is also a category on the regular UIBUtton which has no formal relationship with UIBarButtonItem.
Try getting a UIButton category to work with a regular ViewController first before experimenting with UIBarButtonItem (which does not inherit from UIButton).
UIBarbuttonItem has no initWithFrame, because the thing that organises the bar (UINavigationBar or UIToolbar) - in this case a Navigation Controller - is responsible for it's ultimate size and positioning. The viewController governs the relative order of barButtonItems, and whether they appear on the left or the right, and the content and (some aspects of) it's appearance, but the rest is up to the NavController.

Change IBOutlet text to property of object returned from custom class

I'm using xCode 4.2.1 - I have an app that uses a web service and fetches some data using a custom class and NSURLConnection. The user taps a "refresh" button which starts a series of events that happen in some custom classes in my project, and I can get the object, along with the properties I want to return in a method in the MainViewController, I'm just not able to change the text of an IBOutlet to a property (NSString) of the returned object.
In my "MainViewController.h, I have an IBOutlet (and it's wired to a button in the MainViewController.xib):
IBOutlet UILabel *textLabel;
and:
#property (nonatomic, retain) IBOutlet UILabel *textLabel;
And I've synthesized the label in MainViewController.m
#synthesize textLabel;
The process looks like this: Refresh Button Tapped --> Fires a mthod in MainViewController --> Fires another method in a custom class (retrieves data from web, creates object) --> Sends Object to MainViewController via: (in my custom class implementation)
// parsing, etc.. and define a string for priceString property of mp object
MainViewController *mvc = [[MainViewController alloc] init];
[mvc log:mp];
And in my MainViewController.m I can access a property of that object and print it in NSLog just fine from this method.
- (void) log:(Price *)mp {
self.textLabel.text = mp.priceString;
NSLog(#"%#", mp.priceString);
}
At this point, I can see the data in the log, but the textLabel text won't change.
I've been trying to read examples for a week, and I've heard everything from delegation, to NSNotication answers, but nothing seems to work.
All I need to do is populate an IBOutlet from a -(void) method.
Any help would be greatly appreciated, and I'm down for implementing delegation, but I'm very new to it, and seeking an example.
EDIT - more details.
After further research, I think I should note that my NSURLConnection that is returning my objects is in a separate class, and I've been reading a lot of threads where people are starting the connection in viewDidLoad.
The problem is that you are calling [mvc log:mp]; just after initializing the view controller. At that stage, the view is still not loaded from the xib file.
you can change log to see that:
- (void) log:(Price *)mp {
if (self.textLabel) {
self.textLabel.text = mp.priceString;
} else {
NSLog(#"textLabel is nil.");
}
}
You can call [mvc log:mp]; in the view controller viewDidLoad method, or after viewDidLoad has been executed.
To understand this better, add NSLog(#"viewDidLoad."); in viewDidLoad method, and add NSLog(#"viewController initialized."); just after the code where you initialized the view controller.
You will see the following
viewController initialized.
textLabel is nil. // if you call log as usual after initializing the view controller.
viewDidLoad.

Getting around IBActions limited scope

I have an NSCollectionView and the view is an NSBox with a label and an NSButton. I want a double click or a click of the NSButton to tell the controller to perform an action with the represented object of the NSCollectionViewItem. The Item View is has been subclassed, the code is as follows:
#import <Cocoa/Cocoa.h>
#import "WizardItem.h"
#interface WizardItemView : NSBox {
id delegate;
IBOutlet NSCollectionViewItem * viewItem;
WizardItem * wizardItem;
}
#property(readwrite,retain) WizardItem * wizardItem;
#property(readwrite,retain) id delegate;
-(IBAction)start:(id)sender;
#end
#import "WizardItemView.h"
#implementation WizardItemView
#synthesize wizardItem, delegate;
-(void)awakeFromNib {
[self bind:#"wizardItem" toObject:viewItem withKeyPath:#"representedObject" options:nil];
}
-(void)mouseDown:(NSEvent *)event {
[super mouseDown:event];
if([event clickCount] > 1) {
[delegate performAction:[wizardItem action]];
}
}
-(IBAction)start:(id)sender {
[delegate performAction:[wizardItem action]];
}
#end
The problem I've run into is that as an IBAction, the only things in the scope of -start are the things that have been bound in IB, so delegate and viewItem. This means that I cannot get at the represented object to send it to the delegate.
Is there a way around this limited scope or a better way or getting hold of the represented object?
Thanks.
Firstly, you almost never need to subclass views.
Bind doesn't do what you think - you want addObserver:forKeyPath:options:context: (You should try to understand what -bind is for tho ).
When you say "the key seems to be it being the "prototype" view for an NSCollectionViewItem" I think you are really confused…
Forget IBOutlet & IBAction - they don't mean anything if you are not Interface Builder. "Prototype" means nothing in Objective-c.
The two methods in the view do not have different scope in any way - there is no difference between them at all. They are both methods, equivalent in every way apart from their names (and of course the code they contain).
If wizardItem is null in -start but has a value in -mouseDown this is wholly to do with the timing that they are called. You either have an object that is going away too soon or isn't yet created at a point you think it is.
Are you familiar with NSZombie? You will find it very useful.

Unable to write to NSTextField from Model Controller object

After always running monolithic blocks of code from within my AppController object, I've just learned how to modularize my code using separate model controller objects (so much neater and less confusing to work with :-))
My simple test app has a main AppController and two model objects (Model1 and Model2). I can successfully pass data from the AppController to the models, and the models themselves can run methods and process the passed data 'internally' as they were intended to do -- but I can't get them to communicate with a darned NSTextField in the UI. Here's the relevant parts of my code:
In AppController.m #import "AppController.h"
#implementation AppController
- (IBAction)passObjectsToModelController:(id)sender
{
NSString *stringToPass = #"Hello from Model2 :-)";
int numToPass=12345;
Model2 *ObjController2 = [[Model2 alloc]initWithStuff:stringToPass:numToPass];
[ObjController2 release];
}
#end
...in Model2.h
#import
#interface Model2 : NSObject
{
IBOutlet NSTextField *passedStringField;
}
- (id)initWithStuff:(NSString*)passedString :(int)passedNum;
#end
...and finally in Model2.m
#import "Model2.h"
#implementation Model2
- (id)initWithStuff:(NSString*)passedString :(int)passedNum
{
if(self = [super init])
{
NSLog(#"now inside 'Model2' controller...");
NSLog(#"the passed string reads: %#",passedString); //••• this works •••
NSLog(#"the passed number is:%d",passedNum); //••• this works •••
[passedStringField setStringValue:passedString]; //••• WTF!!... this DOESN'T work! •••
// do something internally with passedNum here...
}
return self;
}
#end
Both model objects have outlets to the common NSTextField and I've control-dragged from both objects to the field and connected them. My AppController doesn't know about the NSTextField (and I assume, doesn't even want to know). No IB connections have been made between the controller object and model objects.
NSLog tells me that the model objects are being created, and that the passed values are making it that far... but not from there into the text field in the GUI window. I'm not getting any compiler errors or warnings. Am I missing some kind of 'setTarget:' call perhaps?
Any help/ideas would be much appreciated. Thanks :-)
Aside from the lack of MVC that mihirsm mentions, the actual problem is that you're trying to access an outlet in an -init method.
When a object is initialized, outlets are not guaranteed to be connected.
If you want to set the value of an NSTextField declared as an outlet, you should implement -awakeFromNib, which is called when the nib has been loaded and all outlets are guaranteed to be live.
in Model1.h:
#interface Model1 : NSObject
{
IBOutlet NSTextField* passedStringField;
NSString* modelString;
}
- (id)initWithString:(NSString*)passedString number:(int)passedNum;
#end
in Model1.m:
#implementation Model1
- (id)initWithString:(NSString*)passedString number:(int)passedNum
{
if(self = [super init])
{
//copy the string to our ivar
modelString = [passedString copy];
}
return self;
}
//awakeFromNib is called when our outlet is live
- (void)awakeFromNib
{
[passedStringField setStringValue:modelString];
}
//don't forget to release the string, because we created it using -copy
- (void)dealloc
{
[modelString release];
}
#end
The Controller sits between the Model and the View. The Model should not communicate with the View.
It should be the job of the Controller to pass any incoming values from the View to the Model. The Model then processes the data and sends back to the Controller which then updates the View with the new data.
So, in your code you should only have one IBOutlet for the TexField declared in the AppController.
Given all this, I am not exactly sure why the TextField is not being updated. From the given code looks like it should. Maybe multople IBOutlets are causing some issue? Can you try with only one Model having the IBOutlet?

Which delegate method should I use to respond to clicks on an NSTextField?

I am trying to respond to a click within a textfield. When the click occurs, I am going to open a panel. My initial thought was to use a delegate method to respond to the click event - but I found that:
This method doesn't work:
(void)textDidBeginEditing:(NSNotification *)aNotification
This method does work, but only when I actually edit the text within the text field, not when I first click it. And - if I edit the text a second time, this method stops working:
(void)controlTextDidBeginEditing:(NSNotification *)aNotification
I could use as much detail as possible - or a code example, ideally. I know that an nstextfield inherits from NSControl, which has a mouseDown event. Is there a similar way to respond to the event with a textfield, also?
Since NSTextField inherits from the NSControl class, it also inherits the -(void)mouseDown:(NSEvent*) theEvent method.
I needed to have an NSTextField call a delegate function upon clicking it today, and thought this basic code might be useful. Note that NSTextField already has a delegate and that in SDK v10.6, the delegate already has a protocol associated with it. Note that if you don't care about protocols, compiler warnings, etc., you don't need the protocol and property declarations or the getter and setter.
MouseDownTextField.h:
#import <Appkit/Appkit.h>
#class MouseDownTextField;
#protocol MouseDownTextFieldDelegate <NSTextFieldDelegate>
-(void) mouseDownTextFieldClicked:(MouseDownTextField *)textField;
#end
#interface MouseDownTextField: NSTextField {
}
#property(assign) id<MouseDownTextFieldDelegate> delegate;
#end
MouseDownTextField.m:
#import "MouseDownTextField.h"
#implementation MouseDownTextField
-(void)mouseDown:(NSEvent *)event {
[self.delegate mouseDownTextFieldClicked:self];
}
-(void)setDelegate:(id<MouseDownTextFieldDelegate>)delegate {
[super setDelegate:delegate];
}
-(id)delegate {
return [super delegate];
}
AppDelegate.h:
#interface AppDelegate <MouseDownTextFieldDelegate>
...
#property IBOutlet MouseDownTextField *textField;
...
AppDelegate.m:
...
self.textField.delegate = self;
...
-(void)mouseDownTextFieldClicked:(MouseDownTextField *)textField {
NSLog(#"Clicked");
...
}
...
If you're building with 10.5 SDK, don't have the protocol inherit from NSTextFieldDelegate.

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