I am trying to programmatically change the user interface of a UIViewController from another NSObject class. The problem is that I am unsure of how to access the UIViewController's view from the NSObject class. So for example, in my NSObject class, I say something like:
self.view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
self.view.backgroundColor = [UIColor yellowColor];
but I keep getting errors saying "Request for member "view" in something not a strut or union." Is there something I need to allow my NSObject class to see my UIViewController?
Whenever you say "self" in a method, it refers to whatever object owns that method. So when you say self.view, you are really asking for the NSObject's view (which, needless to say, doesn't exist, unless you have specifically subclassed the NSObject to have a "view" property.
What you should do is give the NSObject class a property called myController or something in its interface declaration, or pass a ViewController* to any methods that need to access it.
For the property, you can say:
ViewController* myController;
in the NSObject sub-class interface declaration, or for the method way, add an argument to your NSObject sub-class' method:
- (void) someMethodThatTakesAViewController: (ViewController*) theViewController {
//Do your stuff here
theViewController.view = [[UIView alloc] init]; // Or whatever you want to do
}
Hope this was what you were looking for.
In the header file for the object that is trying to change the view, add #class <YOURVIEWCONTROLLER>;, then in the #interface section, add <YOURVIEWCONTROLLER> *viewController; then outside #interface add #property (nonatomic, retain) <YOURVIEWCONTROLLER> *viewController;. Then in the main file add #synthesize viewController; and #import "<YOURVIEWCONTROLLER.h". Then, to change the background colour, use viewController.view.backgroundColor = [UIColor <COLOUR>];.
e.g:
Test.h:
#import <UIKit/UIKit.h>
#class Test2ViewController;
#interface Test : UIViewController {
Test2ViewController *viewController;
}
#property (nonatomic, retain) Test2ViewController *viewController;
Test.m:
#import "Test.h"
#import "Test2ViewController.h"
#implementation Test
#synthesize viewController;
...
viewController.view.backgroundColor = [UIColor yellowColor];
...
Hope this helps
Edit: Make sure to call [viewController release] in your dealloc, otherwise you will have a leaky pipe ;)
you can't access like this... you need to somehow pass UIViewController's view in your NSObject class...
You can typecast your id to UIViewcontroller, like
[((UIViewController *)yourID).view addSubview:yourView.view];
Related
I'd like to design a UIView and some sub-views (UIWebView, UIToolbar, some UIBarButtonItems, a progress indicator and so-forth) using the Interface Builder, but I think it's unnecessary to do this traditionally, by using a UIViewController, using presentViewController:animated etc.
So, I created a custom class, with the .h file code as follows:
#interface FileInteractionManager : NSObject {
}
#property (nonatomic, retain) IBOutlet UIView *fileView;
#property (nonatomic, retain) IBOutlet UIWebView *fileWebView;
#property (nonatomic, retain) IBOutlet UIBarButtonItem *printButton;
#property (nonatomic, retain) IBOutlet UIBarButtonItem *optionsButton;
#property (nonatomic, retain) IBOutlet UIBarButtonItem *doneButton;
My .m file is as follows:
#implementation FileInteractionManager
#synthesize fileView, fileWebView, doneButton, optionsButton, printButton;
-(id)init {
NSArray *array = [[NSBundle mainBundle] loadNibNamed:#"FileInteractionView" owner:self options:nil];
NSLog(#"Load success!");
return self;
}
Finally, I create a stand-alone xib file named 'FileInteractionView.xib', change the file's owner to the custom class I created above, and wire up the IBOutlets.
When I call the init method on my class, I can see in the debugger that all my IBOutlet objects are instantiated properly.
My questions are:
Is the loadNibNamed:owner:options: method the right way to load my stand-alone .xib file? I don't like the fact that this method returns an array I have no use for (the top-level object returned matches my variable fileView, but I've already linked them through the Interface Builder).
Is my general approach correct in solving my problem? I carried out the above steps because I wanted a simple UIView object that I could add to my existing UIViewController, rather than present and dismiss a whole new UIViewController.
I use a little different approach. I create a subclass of UIView (MyCustomView i.e.) then the xib with the UI of the view and change the (main) view class the the one just defined. In the xib then you can link the outlet to the custom view itself (not the file owner).
Finally in the class definition I create a function like this:
+ (id) newFromNib
{
NSArray *nibArray = [[UINib nibWithNibName:NSStringFromClass([self class]) bundle:nil] instantiateWithOwner:nil options:nil];
return nibArray[0];
}
Just a couple of notes:
1) this's a class method, you can use "self" just for stuff like "NSStringFromClass([self class])" but the real object is the variable returned
2) this example suppose the xib have the same name of the class (via NSStringFromClass([self class]) so I can copy-paste it without changing anything ;) ) and that your view is the first one defined in the xib (the standard). If you store more than a "main" view inside one xib pick the right element.
so where I need MyCustomView I do something like:
MyCustomView* mycv = [MyCustomView newFromNib];
then set frame/center and add to superview...
I think this way is pretty usefull if you have a "library" of complex UI elements and want to design them via xib then add when needed.
il Malvagio Dottor Prosciutto answer is nice. Here is a possible alternative.
Load nib in NS_DESIGNATED_INITIALIZER and become owner of subview
If we accept the xib to only hold a subview instead of the view itself, then we can load the subview in initWithFrame: and keep an ownership construction in xib.
#interface MyCustomView ()
#property (strong, nonatomic) IBOutlet UIView *subview;
#end
#implementation MyCustomView
- (instancetype)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
[[NSBundle mainBundle] loadNibNamed:NSStringFromClass([self class]) owner:self options:nil];
[self addSubview:self.subview];
return self;
}
#end
I have derived a class SignalView from UIView however when I send a message to my object of type SignalView it gets sent to a UIView and I get error :
-[UIView Initialise]: unrecognized selector sent to instance 0x1b3900
my object also appears as a UIView object in the debug watch window:
m_signalview UIView * 0x001b3900
the relevant code is:
// signalview.h
#import <UIKit/UIKit.h>
#interface SignalView : UIView
{
}
-(void)Initialise;
#end
//signalview.m
#import "SignalView.h"
#interface SignalView ()
#end
#implementation SignalView
-(void)Initialise
{
}
// viewcontroller.h
#import <UIKit/UIKit.h>
#import "SignalView.h"
#interface ViewController : UIViewController
#property (weak, nonatomic) IBOutlet SignalView *m_signalview;
#end
// viewcontroller.m
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize m_signalview;
- (void)viewDidLoad
{
[super viewDidLoad];
NSLog(#"%#", m_signalview);
[m_signalview Initialise];
}
H2C03 is right. its likely not a SignalView. I would check your outlet in your view's nib file in the interface builder inspector make sure it doesn't still say UIView. If it does change it to SignalView:
Should look like this:
Then it's simply an instance of UIView and not a SignalView. You're allocating and initializing UIView when you would need a SignalView instance. When you have something like this in your code:
m_signalView = [[UIView alloc] init];
change it to
m_signalView = [[SignalView alloc] init];
I see that m_signalview is an IBOutlet.
Are you connecting that to a UIView you added in Interface Builder?
If so you might need to set the right class in its properties so that the loader can create an object of the right class.
I'm having some trouble understanding what classes can read what variables in other classes. I've read to many different things online and cant seem to find anything solid in here. I've literally wasted the past two days trying to get my program to work but no classes can read any other classes variables. Any help will be GREATLY appreciated.
This is my ViewController.h:
#interface ViewController : UIViewController
{
#public
NSString *nameOfLabel;
}
#property (strong, nonatomic) IBOutlet UILabel *firstLabel;
- (IBAction)Switch:(id)sender;
- (IBAction)changeLabel:(UIButton *)sender;
-(NSString *) nameOfLabel;
#end
nameOfLabel is a public variable and should be able to be accessed by an outside class, right?
ViewController.m:
#import "ViewController.h"
#import "NewView.h"
#interface ViewController ()
#end
#implementation ViewController
- (IBAction)Switch:(id)sender {
NewView * new = [[NewView alloc] initWithNibName:nil bundle:nil];
[self presentViewController: new animated:YES completion:NULL];
}
- (IBAction)changeLabel:(UIButton *)sender {
nameOfLabel = #"Test Name";
_firstLabel.text = nameOfLabel;
}
-(NSString *) nameOfLabel {
return nameOfLabel;
}
#end
changeLabel button changes *firstLabel.text to "Test name".
second class is NewView.h:
#import "ViewController.h"
#interface NewView : UIViewController
#property (strong, nonatomic) IBOutlet UILabel *secondLabel;
- (IBAction)changeSecondLabel:(UIButton *)sender;
#end
and NewView.m:
#import "NewView.h"
#interface NewView ()
#end
#implementation NewView
{
ViewController *view;
}
- (IBAction)changeSecondLabel:(UIButton *)sender {
view = [[ViewController alloc] init];
_secondLabel.text = view.nameOfLabel;
}
#end
changeSecondLabel should change secondLabel.text to nameOfLabel which is 'Test name', however, the label actually disappears which makes me think that nameOfLabel cannot be reached. Ive played around with nameOfLabel, making it a #property and then synthesising it, as well as trying putting it in { NSString *nameOfLabel; } under #implementation but I still get the same result.
This line: view = [[ViewController alloc] init]; creates a new ViewController which doesn't know anything about what you may have done to some other ViewController. In your case, it specifically doesn't know that changeLabel: was called on another ViewController before this new one ever existed.
When the second view controller (NewView) is presented, it has no reference to the first view controller (ViewController) and it's data.
Here are a couple of suggestions.
In modern Objective-C I'd recommend using properties instead of exposing a variable.
Look over the naming in general. "ViewController" is not a good name for example.
If the property is part of an internal state of the class, declare it in a class extension.
Before you present the second view controller, set a reference to the string from the first view controller.
Part of ViewController.m:
#interface ViewController ()
#property (copy,nonatomic) NSString *nameOfLabel;
#end
#implementation ViewController
- (IBAction)Switch:(id)sender {
NewView *new = [[NewView alloc] initWithNibName:nil bundle:nil];
new.secondLabel.text = self.nameOfLabel;
[self presentViewController: new animated:YES completion:NULL];
}
First of all please read about coding standards, it's not a good practice to:
Name variables like "new"
Name methods like "Switch"
Name UIViewController like "view" or "NewView"
Regarding logic:
This is all messed up here. What you actually do is you create viewController with nameOfLabel which is empty and is only changed on button press. I assume you press that button so it's changed. Then on switch action you create another viewController and present it. Then from inside that new viewController you create another new viewController which has empty nameOfLabel, get this empty value and put it inside secondLabel.
There are couple of ways you can do to change secondLabel:
Move nameOfLabel to model and read it from there when you want to change secondLabel,
Because your new viewController is child of viewController that keeps nameOfLabel you can access it by calling [[self presentingViewController] nameOfLabel] but make it property first,
Pass nameOfLabel through designated initializer.
Well, if you want a simple demonstration of access of a public ivar, the syntax is:
view->nameOfLabel;
^^
not dot-syntax:
view.nameOfLabel;
(dot-syntax just goes through accessor methods).
I've only seen a handful of warranted edge cases over the years; there's rarely, rarely ever a good reason to make an ivar public (also, protected is also rarely a good choice).
I have a Subclass of NSObject in which I want to call IMMEDIATELY (a sort of -(void)viewDidLoad) a method (in this case to load a MkMapView): what's the better way to do this? I think I cant use viewDidLoad, so can I use performSelector?
SubClass.h
#interface Mysubclass : NSObject <MKMapViewDelegate> {
}
SubClass.m (1st alternative)
-(id)init{
self = [super init];
if ( self != nil ) {
// THE CODE TO INITIALIZE MKMAPVIEW
}
return self
}
OR
SubClass.m (2nd alternative)
-(id)init{
[self performSelector:#selector(myMethod)];
return self;
}
-myMethod{
// THE CODE TO INITIALIZE MKMAPVIEW
}
What's the better (or correct) alternative? Its possible to avoid -(id)init? Or everytime I add a subclass, to call a method I have to write it into -(id)init? Thank you!
There is no reason to use -performSelector: in this context. If you want to add a method that initializes the MKMapView when your object is created, call the method from within the if (self) block:
- (id)init
{
self = [super init];
if (self) {
[self setupMapView];
}
return self;
}
- (void)setupMapView
{
// THE CODE TO INITIALIZE MKMAPVIEW
}
It is a matter of personal preference/style whether to have a second method -setupMapView or to simply leave the code for setting up the MKMapView in the if (self) block of the -init method or to break the code off into a second method -setupMapView called from -init.
That being said, it sounds like other things may be off with your setup. Your MKMapView should [most likely] be within a UIViewController subclass (which will probably have an associated XIB), so you will be have access to -viewDidLoad. Note that your UIViewController subclass will serve as the delegate to your MKMapView.
Update 1
In your UIViewController subclass instance (I'll assume you called it ViewController, you should have an IBOutlet to an MKMapView object. Do this in ViewController.h either by (1) adding an instance variable
#interface ViewController : UIViewController
{
IBOutlet MKMapView *myMap;
}
#end
or by (2) adding a property
#interface ViewController : UIViewController
#property (nonatomic, strong, readwrite) IBOutlet MKMapView *myMap;
#end
Now open ViewController.xib in Interface Builder. You should have an MKMapView inside the view. If you don't already, add one from the Object Library. Right click on File's Owner. Locate the row with the item myMap. Drag from the circle on the right end of the row to the MKMapView in the visible view.
Your ViewController class now has an outlet to the MKMapView. You will be able to send messages to the MKMapView subview of your view controllers view after it has been loaded.
You should have a property or an instance variable for your SubClass instance so that it doesn't get destroyed as soon as -viewDidLoad returns. Do this again by either adding an instance variable to ViewController.h
#interface ViewController : UIViewController
{
IBOutlet MKMapView *myMap;
SubClass *istance;
}
#end
or by adding a property
#interface ViewController : UIViewController
#property (nonatomic, strong, readwrite) IBOutlet MKMapView *myMap;
#property (nonatomic, strong, readwrite) SubClass *istance;
#end
Now, in ViewController.m, you need to define -viewDidLoad so that self.istance is set as the delegate of self.myMap. In the comments, I had suggested creating your own initializer -initWithMapView:. If you plan on having SubClass do some extensive set-up of your MKMapView, that makes sense. If you just want SubClass to be the delegate of the MKMapView, there's no need for such a method.
Let's consider both cases:
(1) using a method -[SubClass initWithMapView:]:
In ViewController.m you'll have (within the #implementation of ViewController)
- (void)viewDidLoad
{
self.istance = [[SubClass alloc] initWithMapView:self.myMap];
}
In SubClass.h you'll have (within the #interface of SubClass)
- (id)initWithMapView:(MKMapView *)mapView;
#property (nonatomic, weak, readwrite) MKMapView *mapView;
In SubClass.m you'll have (within the #implementation of SubClass)
- (id)initWithMapView:(MKMapView *)mapView
{
self = [super init];
if (self) {
self.mapView = mapView;
self.mapView.delegate = self;
//more setup of mapView.
}
return self;
}
(2) using -[SubClass init]:
Instead, in ViewController.m you'll have
- (void)viewDidLoad
{
self.istance = [[SubClass alloc] init];
self.myMap.delegate = self.istance;
}
New to iOS/Objective-C here. I've spent a lot of time trying to figure this out, but just can't manage it. Here's what's happening:
Click a 'Graph' button on my RootViewController's view
GraphViewController takes over, has a graphView property
I set the graphView's dataSource property to self
Checking self.graphView.dataSource with NSLog confirms that it does indeed point to self
When GraphView's drawRect: is called, self.dataSource is set to (null), where I expected it to point to the GraphViewController object
To summarise: I'm instantiating the graphView property in the view controller, then setting its dataSource, but by the time the view's drawRect: is called the dataSource is no longer set.
GraphViewController.m:
#import "GraphViewController.h"
#import "GraphView.h"
#implementation GraphViewController
#synthesize graphView = _graphView;
#synthesize program = _program;
- (GraphView *)graphView {
if(!_graphView) {
_graphView = [[GraphView alloc] init];
[_graphView setDataSource:(id)self];
}
return _graphView;
}
#end
GraphViewController.h:
#import <UIKit/UIKit.h>
#import "GraphView.h"
#interface GraphViewController : UIViewController
#property (strong, nonatomic) IBOutlet GraphView *graphView;
#end
GraphView.m:
#import "GraphView.h"
#implementation GraphView
#synthesize dataSource = _dataSource;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
NSLog(#"initWithFrame called, self.dataSource=%#", self.dataSource);
}
return self;
}
- (void)drawRect:(CGRect)rect
{
NSLog(#"drawRect:");
NSLog(#"\tself=%#", self);
NSLog(#"\tself.dataSource=%#", self.dataSource); // is (null), shouldn't be
[self.dataSource programToGraph];
}
#end
GraphView.h:
#import <UIKit/UIKit.h>
#class GraphView;
#protocol GraphViewDataSource
- (id)programToGraph;
#end
#interface GraphView : UIView
#property (nonatomic, weak) IBOutlet id <GraphViewDataSource> dataSource;
#end
So it looks like the GraphViewController instance is being deallocated, which will nil out the dataSource property.
So you should go back and look at how you are creating and managing that GraphViewController. A common mistake is to create a view controller like that, then borrow its view and throw it into some other view controller's view hierarchy, and then let the original view controller just go away.
I would look at that, and if you don't see it there, post the code where you create and present the GraphViewController.
Oh, and where are you calling initWithFrame: from?? It almost looks like you could also have two different instances of GraphView floating around. Try logging 'self' along with self.datasource to check that also.