I need to programmatically delegate various events which occur in the main view to handlers that are instantiated by the main ViewController.
In other words, instead of having the ViewController handle all the events for a given view I would like to have separate instantiated objects handle the events for subsections of the overall view.
A numbered bulleted list describing how to implement this, or a link to a numbered bulleted list would be highly helpful. If you included an explanation which used examples from Java's Swing API as analogous operations you would earn a special place in my heart.
Here is my current half-baked code. I include it so you know I have tried to solve this before resorting to Stack Overflow.
TCH_MainViewController.m
#import "TCH_MainViewController.h"
#import "TCH_MainViewButtonHandler.h"
#interface TCH_MainViewController ()
#property (nonatomic, weak) IBOutlet UILabel *titleLabel;
#property (nonatomic, weak) TCH_MainViewButtonHandler *buttonHandler;
#property (nonatomic, weak) UIButton *changeColorButton;
#end
#implementation TCH_MainViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
[_changeColorButton addTarget:_buttonHandler action:#selector(changeColorButton) forControlEvents:UIControlEventTouchUpInside];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
TCH_MainViewButtonHandler.m
#import "TCH_MainViewButtonHandler.h"
#implementation TCH_MainViewButtonHandler
- (IBAction)changeLabelColor:(id)sender{
}
-(void)awakeFromNib{
}
#end
you do have the selector signature wrong, but you also need to initialize your handler class first either directly or lazily. Oh yea, and the property for the handler should be strong, not weak as you need your main class to retain the handler class. I'm assuming the button is on a Storyboard or Xib file. In that case it's good for the button to be weak because the Storyboard is retaining it strongly. If you class did as well, that would create a retain cycle.
Correct the property:
#property (nonatomic, strong) TCH_MainViewButtonHandler *buttonHandler;
Initialize the class before you set the selector on the button.
self.buttonHandler = [TCH_MainViewButtonHandler alloc]init];
note: probably a better practice to access the property via self rather then its instance _button..
then set the target on the button:
[self.changeColorButton addTarget:self.buttonHandler action:#selector(changeColorButton:) forControlEvents:UIControlEventTouchUpInside];
Note: the colon on the end of the selector is usually added if you let Xcode autocomplete. It references the parameter "sender" in this case.
Add a little NSLog(#"button pressed"); in the button action in your button handler and see if that does not get called. It should.
Now, normally UI events like button pushes are not normally delegated away because they end up doing something to the view and that needs to come from the controller managing the view. Although for a network call you might do it. If your button push is affecting the view i.e updating an label, you'll need to come back to the view controller for that purpose. So you have to think through that.
However, per your question, this answer should get you to the next step.
hope that helps,
best wishes.
Your selector is #selector(changeColorButton) when I believe it should be #selector(changeLabelColor:).
Related
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 have UIViewController named ParentViewController.h and .m
Then I added UIView inside this ParentViewController.
I had uiview.h and uiview.h added and assigned to UIView inside ParentViewController.
From
-(void)drawRect:(CGRect)rect {}
which is located in uiview.m, I need to access to properties inside ParentViewController.
How do I do this? Am I using UIView wrong?
ParentViewController.h
#import <UIKit/UIKit.h>
#interface ParentViewController : UIViewController
//I want my uiview to access this variable.
#property (nonatomic, strong) NSMutableArray *usedByUIView;
#end
ParentViewController.m
#import "ParentViewController.h"
#import "uiview.h"
#implementation ParentViewController
- (void)viewDidLoad {
...
}
#end
uiview.h
#import <UIKit/UIKit.h>
#interface uiview : UIView
#end
uiview.m
#import "uiview.h"
#implementation uiview
-(id) initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if(self){
}
return self;
}
- (void)drawRect:(CGRect)rect {
NSLog(#"start drawing using the data from usedByUIView");
}
#end
There are a few answers on this subject but, summarizing them, you don't, at least not the way that you're doing it. UIView's do not have access to their view controller's and aren't supposed to need access. Of course, in the real world, sometimes it's not worth the overhead of coding around independent views so people hack in access to the controller access. This can be done by keeping an instance variable in the view, pointing to the controller, and assigning a reference to it after the view has loaded, or by overriding the init so you also pass a view controller, or lots of other ways. But before you do that think through the logic of why you want access to the controller from the view and see if there isn't a different way to do it.
I'm completely new to Objective-C, XCode, and iOS development and I'm trying to figure out how to run certain code at startup, after all UI views and controls have been instantiated. I have a generic NSObject that I've added through interface builder by dragging it into my view controller scene. It's defined as follows:
#import <Foundation/Foundation.h>
#interface Controller : NSObject {
IBOutlet UISlider *slider;
IBOutlet UILabel *label;
}
-(IBAction)sliderChanged:(id)sender;
#end
I need to run sliderChanged on initialization. I've tried the following way:
#import "Controller.h"
#implementation Controller
-(id)init {
self = [super init];
if (self){
[self sliderChanged:nil];
}
return self;
}
// More code here
But both my slider and label are nil when this is called. I understand there's a viewDidLoad method within the ViewController class which may be what I need, but I'm not sure how to access the instance of my Controller class (which seems to be instantiated somewhere behind the scenes by the interface builder) from within that method. Should all of this code simply be moved to the ViewController itself? That would seem to make sense, but the design above is what we've been instructed in class, so I'm not really sure how to go about doing this.
After the XIB/Storyboard loader finishes loading all the objects and wiring them up, it sends awakeFromNib to every object that was instantiated from the XIB. So try adding this to your Controller class:
- (void)awakeFromNib {
[super awakeFromNib];
[self sliderChanged:nil];
}
You can find more information in the NSObject UIKit Additions Reference and “The Nib Object Life Cycle” in the Resource Programming Guide.
HOWEVER, if you created Controller as a top-level object, and you didn't connect any outlets to it, then nothing references it after the XIB loader finishes with it, so the system will deallocate it again. That's probably not what you want, so you should connect an outlet in your view controller to the Controller. If you do that (and let's say the outlet is named controller), then you can access it in viewDidLoad in your view controller class:
#import <UIKit/UIKit.h>
#import "Controller.h"
#interface ViewController : UIViewController {
IBOutlet Controller *controller;
}
#end
Implementation:
- (void)viewDidLoad {
[super viewDidLoad];
[self.controller sliderChanged:self];
}
In my project I used storyboard and when I accessed an UI element I created a property and linked it. This property is weak. To my understanding the property can be weak since it is already added to the view and the views retains it.
In an other project I do not use storyboard. Now I am not sure how to define a UI element. I think this can be done both, situation 1:
#interface LoginView
#property (strong, nonatomic) UIButton *login
#end
- (instancetype) init {
if (self == [super init]) {
_login = [UIButton buttonWithType:UIButtonTypeCustom];
[self addSubview:_login];
[self setNeedsUpdateConstraints];
}
return self;
}
Situation 2:
#interface LoginView
#property (weak, nonatomic) UIButton *login //<<notice weak
#end
- (instancetype) init {
if (self == [super init]) {
UIButton login = [UIButton buttonWithType:UIButtonTypeCustom];
[self addSubview:login];
_login = login
[self setNeedsUpdateConstraints];
}
return self;
}
My question is: "Can both situation be used? If so is there a preferred way?"
Own ideas: I think situation two is preferred since it doesn't create a second strong pointer?
Either will work fine.
Personally I prefer strong, so that I'm not relying on another view retaining something.
Also strong has slightly less overhead as opposed to a weak reference which needs to be tracked and zeroed to nil automatically (not that you would notice this time difference).
You can still use weak reference because the views super view will be having strong reference to it.
So I'm trying to get a hang of using delegates, and I've watched a few tutorials on how to use them so far. I still find them confusing and after trying to implement one myself, have an issue that I can't seem to solve.
I have two ViewControllers, the first one ViewController contains a UITextField *sampleTextField and a button with the method switchViews. It also contains the protocol declaration with the method sendTextToViewController. SwitchViews is also linked to a segue that switches to the SecondViewController. In SecondViewController the only object is a UILabel *outputLabel When the user taps the button, it calls switchViews and the view changes to SecondViewController, and upon loading outputLabel should be changed to whatever text was entered in sampleTextField in ViewController. However the delegate method sendTextToViewController is never being called. All objects are created in Interface Builder.
Here is the code to make it a bit easier to understand:
ViewController.h
#import <UIKit/UIKit.h>
#protocol TextDelegate <NSObject>
-(void)sendTextToViewController:(NSString *)stringText;
#end
#interface ViewController : UIViewController
- (IBAction)switchViews:(id)sender;
#property (weak, nonatomic) IBOutlet UITextField *sampleTextField;
#property (weak, nonatomic) id<TextDelegate>delegate;
#end
Then declared this in ViewController.m
- (IBAction)switchViews:(id)sender {
NSLog(#"%#", self.sampleTextField.text);
[self.delegate sendTextToViewController:self.sampleTextField.text];
}
SecondViewController.h
#import <UIKit/UIKit.h>
#import "ViewController.h"
#interface SecondViewController : UIViewController <TextDelegate>
#property (weak, nonatomic) IBOutlet UILabel *outputLabel;
#end
SecondViewController.m
#import "SecondViewController.h"
#interface SecondViewController ()
#end
#implementation SecondViewController
#synthesize outputLabel;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
ViewController *vc = [[ViewController alloc]init];
[vc setDelegate:self];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(void)sendTextToViewController:(NSString *)stringText
{
NSLog(#"Sent text to vc");
[outputLabel setText:stringText];
}
I've looked at this and the first answer makes sense, but for some reason it's not working.
I do think that the problem is where I am setting calling [vc setDelegate:self], but not sure how to fix this. Some pointers in the right direction would be greatly appreciated. Keep in mind I'm new to obj-c so if you can explain what you are saying, that would be great. Thank you.
Your are creating a new instance of ViewController but you don't do anything with it.
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
ViewController *vc = [[ViewController alloc]init];
[vc setDelegate:self];
}
The SecondViewController needs to have reference to the FirstViewController to be able to set itself as a delegate.
First you don't have to use delegation to do such a program.
A simpler way would be just creating a property in the SecondViewController that you'll pass the content of the textField into it.
Your code doesn't work because you called sendTextToViewController on a delegate that hasn't been set. You have set the delegate to a new instance of ViewController, not the one presented onscreen.