I've been trying to make this work for a while now with no chance, every time I change from view to view, the view's variables and content are reset to 'default' e.g if in a view I changed a label's text field from the default 'Label' to 'Hello, and then change views, once I come back to the same view, the text will be 'Label' again.
The only way I've gotten around this so far is to set a static string and then change Label.text to string in viewDidLoad. I just KNOW that this isn't the way to do it. I have a hunch that it's to do with how I transition from view to view, (allocating and initiating etc.)
Current way I transition:
FirstView.h:
#interface FirstView : Engine
#property(nonatomic, readwrite) MainGameDisplay *secondView;
FirstView.m:
#implementation FirstView
- (IBAction)StartGame:(id)sender
{
if (! self.secondView)
self.secondView = [[MainGameDisplay alloc] initWithNibName:nil bundle:nil];
[self presentViewController: self.secondView animated:YES completion:NULL];
}
And MainGameDisplay:
MainGameDisplay.h:
#class ViewController;
#interface MainGameDisplay : Engine
#property (strong) ViewController *firstPage;
MainGameDisplay.m:
#implementation MainGameDisplay
- (IBAction)returnToHome:(id)sender {
if (!self.firstPage)
self.firstPage = [[ViewController alloc] initWithNibName:nil bundle:nil];
[self presentViewController: self.firstPage animated:YES completion:NULL];
}
What I would like is to not have to set all of the values again through viewDidLoad, I just cant see it as being a good programming style.
You're right in your suspicions about what's gone wrong. Although you call your method returnToHome: you aren't really returning anywhere but rather stacking a new copy of ViewController on top of whatever you already have.
To actually go back, the opposite of presentViewController: is dismissViewControllerAnimated:. Try using that inside your MainGameDisplay class when the button is pressed to go back.
Related
I have a NSViewController and a corresponding .xib file.
In the nib file, there's a NSPanel.
I link the NSPanel to the ViewController:
#property (strong) IBOutlet NSPanel *panel;
However, when I wanted to pass panel to my AppDelegate and show on screen, my code didn't work well.
This is part of my code:
//MainViewController.m
-(NSPanel *)passPanel{
if(!self.panel){
NSLog(#"panel is nil");
self.panel = [[NSPanel alloc] init]; //breakpoint
return self.panel;
}else{
NSLog(#"panel is not nil");
return self.panel; //breakpoint
}
}
//AppDelegate.m
MainViewController* vc = [[MainViewController alloc] init];
self.window = [vc passPanel];
I think when I initiate vc, the panel should be initiate as what it's like in the nib file because I've set it as a property.
But why it is always nil?
I've also set breakpoints to debug, I found it not working as I wanted.
In order not to make the question seem confusing, I paste all my code in MainViewController.m below:
#import "MainViewController.h"
#interface MainViewController ()
#end
#implementation MainViewController
#synthesize panel;
- (void)viewDidLoad {
[super viewDidLoad];
// Do view setup here.
}
-(NSPanel*)passPanel{
NSLog(#"passing panel to sender...");
if(!self.panel){
NSLog(#"panel is nil");
self.panel = [[NSPanel alloc] init];
return self.panel;
}else{
NSLog(#"panel is not nil");
return self.panel;
}
}
#end
EDIT
As the code doesn't show clear about the question, I put some screenshots below.
MainMenu.xib
MainViewController.xib
The MainMenu.xib is the default nib file created when the project is created. In this nib file I have a window to show other views. In the MainViewController.xib, I have a NSPanel which is a subclass of NSWindow. Actually I'm not sure it's proper to use a ViewController(MainViewController) to control a window. Now I want to show this NSPanel object. So I assign this panel to my window in MainMenu.xib. It did work(although I felt it's not a good way).
My question is, I think after the window is assigned a NSPanel, the panel would automatically load its view. However, it didn't.
In the passPanel method, it turned out that self.view is nil. So what appear on screen is a blank window.
What I want it to show:
but it shows
I'm showing an NSPopover in an NSView, originating from a point on an NSBezierPath. I'm able to show the popover without a problem, but I can't seem to set the string value of the two text fields in it. The popover and the content view are both a custom subclass of NSPopover and NSViewController, respectively. The NSPopover subclass is also the NSPopover's delegate, although I don't implement any delegate methods, so I'm not sure I even need to do that.
Here is my subclass of NSViewController:
#import <Cocoa/Cocoa.h>
#interface WeightPopoverViewController : NSViewController
#end
#import "WeightPopoverViewController.h"
#interface WeightPopoverViewController ()
#end
#implementation WeightPopoverViewController
- (id)init {
self = [super initWithNibName:#"WeightPopoverViewController" bundle:nil];
if (self) {
}
return self;
}
#end
And my subclass of NSPopover:
#import <Cocoa/Cocoa.h>
#interface WeightPopoverController : NSPopover <NSPopoverDelegate> {
NSTextField *dateLabel;
NSTextField *weightLabel;
}
#property (strong) IBOutlet NSTextField *dateLabel;
#property (strong) IBOutlet NSTextField *weightLabel;
#end
#import "WeightPopoverController.h"
#implementation WeightPopoverController
#synthesize weightLabel;
#synthesize dateLabel;
#end
This is the code in my NSView subclass that opens up the popover:
#interface WeightGraphViewController () {
WeightPopoverController *popover;
WeightPopoverViewController *vc;
}
...
-(void)mouseEntered:(NSEvent *)theEvent {
// initialize the popover and its view controller
vc = [[WeightPopoverViewController alloc] init];
popover = [[WeightPopoverController alloc] init];
// configure popover
[popover setContentViewController:vc];
[popover setDelegate:popover];
[popover setAnimates:NO];
// set labels
for (id key in (id)[theEvent userData]) {
[popover.weightLabel setStringValue:[(NSDictionary*)[theEvent userData] objectForKey:key]];
[popover.dateLabel setStringValue:key];
}
// set the location
(redacted, irrelevant)
// show popover
[popover showRelativeToRect:rect ofView:[self window].contentView preferredEdge:NSMaxYEdge];
}
-(void)mouseExited:(NSEvent *)theEvent {
[popover close];
popover = nil;
}
In WeightPopoverViewController.xib, I've set the File's Owner to WeightPopoverViewController and connected the view to the custom NSView. In this xib I also have an Object set to WeightPopoverController with the dateLabel and weightLabel connected to their text fields and the contentViewController set to File's Owner.
I think where I am going wrong is likely related to how I have configured my class / instance variables for the NSPopover, but from the research I've done and documentation I've read I can't seem to crack where I've gone wrong. Any help would be appreciated.
UPDATE:
I removed the NSPopover subclass from code and from IB. I put my outlets in my NSViewController and connected them in IB. However, I'm still not able to set the string values. The following won't compile with the error "Property 'weightLabel' not found on object of type NSPopover*'".
#interface WeightGraphViewController () {
NSPopover *popover;
...
}
-(void)mouseEntered:(NSEvent *)theEvent {
vc = [[WeightPopoverViewController alloc] init];
popover = [[NSPopover alloc] init];
[popover setContentViewController:vc];
[popover.dateLabel setStringValue:#"test"];
}
I have the property definition exactly as I had it in my NSPopover subclass, but now in my NSViewController. This is actually what I had before, and since I wasn't able to set the properties from the NSViewController, I figured I needed to do it through a subclass of NSPopover. This is why I thought I am having an issue with how I have configured my class / instance variables.
You seem to be creating two popovers, one in code (popover = [[WeightPopoverController alloc] init]) and one in Interface Builder (In this xib I also have an Object set to WeightPopoverController). Have a think about what you’re trying to achieve.
I would also advise against subclassing NSPopover. I believe this is causing confusion and is unnecessary. Instead, put the outlets to your dateLabel and weightLabel in the popover’s content view controller.
I've experienced something that I think is similar. The root problem is that the "outlets" connecting your view (XIB) to your controller are not initialized until after the view has been displayed. If the controller tries to set properties on any UI controls in the view before the popover has been opened, those changes are ignored (since all the controls will be nil).
Luckily, there's an easy solution (as mentioned in this answer): just invoke the view getter on your controller, and it will force the view to initialize sooner.
In other words:
popover = [NSPopover new];
myController = [[MyViewController alloc] initWithNibName:#"MyView" bundle:nil];
popover.contentViewController = myController;
[myController view]; // force view to initialize
...set some values on myController... // works because view is now loaded
[popover showRelativeToRect: ...];
I'm trying to make a button take me to a new UIViewController based on the content of a textField, but when I run it and hit the button (with the right condition in the text field to take me to the new UIViewController), the screen blacks out. This is what I wrote in my .h and .m files. Can anyone help me (Im using storyboards)
#interface ViewController : UIViewController
- (IBAction)boton:(id)sender;
#property (strong, nonatomic) IBOutlet UITextField *texto;
#end
#import "ViewController.h"
#import "ViewController2.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize texto;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)boton:(id)sender {
if ([texto.text isEqualToString:#"1"]) {
ViewController2 *vc1=[[ViewController2 alloc]init];
[self presentViewController:vc1 animated:YES completion:nil];
}
}
#end
As you say the screen is blacking out, I expect your viewController is getting initialised without a view.
To initialise with a view hierarchy from a xib(nib) file:
- (id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)nibBundle
where nibName can be nil if it shares it's name with the View Controller, and nibBundle can be nil it the nib is in the main bundle.
i.e....
ViewController2 *vc2;
vc2 = [[ViewController2 alloc] initWithNibName:nil
bundle:nil];
where the xib file is named ViewController2.xib
To initialise from a storyboard:
UIStoryboard *storyboard = self.storyboard;
vc2 = [storyboard instantiateViewControllerWithIdentifier:#"ViewController2"];
(you need to set up a viewController in storyboard and give it a matching identifier)
To initialise with neither storyboard or xib, you should override your view controller's - (void)loadView, create a view and assign it to self.view.
Update
In answer to your comment - the UIStoryboard... and ViewController2 *vc2= ... code would go into your button code (in your case it you would replace / adapt the line containing vc1=.... It would look like this:
- (IBAction)boton:(id)sender {
if ([texto.text isEqualToString:#"1"]) {
ViewController2 *vc2;
UIStoryboard *storyboard = self.storyboard;
vc2 = [storyboard instantiateViewControllerWithIdentifier:#"ViewController2"];
[self presentViewController:vc2 animated:YES completion:nil];
}
You will need to have created a storyboard scene in your storyboard with a viewController whose custom class is ViewController2 and identifier is "ViewController2". The identifier name is arbitrary, but must match the identifier string you use in your code.
As you are using storyboards, an alternative way to do this is to create a modal segue from the 'ViewController' scene to a 'ViewController2' scene, give it an identifier, and use performSegueWithIdentifier in your button method.
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 know similiar questions have been asked before, but please bear with me as I am totally new at Objective C (have good knowledge on C).
My case is that I have a tab bar controller with two windows. When I press a button in "second" I change a variable changeName. I want to use the value of changeName in my "first" view controller but stumbled on to some problems:
To reach the other viewcontroller I found this from SO (unfortunately I forgot where):
-(NSString *)newName{
// Create a UIStoryboard object of "MainStoryBoard_iPhone" named storyboard
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:(NSString *)#"MainStoryBoard_iPhone" bundle:(NSBundle *)nil];
// Create a UIViewController object of the wanted element from MainStoryBoard_iPhone
UIViewController *secondview = [storyboard instantiateViewControllerWithIdentifier:(NSString *)#"secondBoard"];
return secondview.changeName;
}
Which I have in my first.m. MainStoryBoard_iPhone is the name of the .xib/storyboard-file.
but no. Error says
Property 'changeName' not found on object of type 'UIViewController *'
In my second.h I have
#property (readwrite, retain) NSString *changeName;
and in second.m
#synthesize changeName;
All help is appreciated, but please keep in mind that I have only used OOP for two days.
Thank you all in advance
EDIT: And what input should I have here?
- (void)viewDidLoad
{
[super viewDidLoad];
mylabel.text = Name; // or [mylabel.text Name] or something?
}
You need to cast the view controller returned to your customized second view controller (as UIViewController does not have the property changeName).
So do the following :
// Create a UIViewController object of the wanted element from MainStoryBoard_iPhone
SecondViewController *secondview = (SecondViewController *)[storyboard instantiateViewControllerWithIdentifier:(NSString *)#"secondBoard"];
I assume SecondViewController is the name of your second controller.
In my case I wanted to pass a string from FirstViewController to set a text field in SecondViewController, so:
1- In SecondViewController.h
#property (strong, nonatomic) IBOutlet UITextField *someTextField;// this is linked to a UITextField
2- In FirstViewController.m:
#import "SecondViewController.h"
3- I will do this after a press of a button in the FirstViewController:
SecondViewController *SecondView = [[SecondViewController alloc]
initWithNibName:#"SecondViewController" bundle:nil];
//set fields values
SecondView.someTextField.text = #"HeLLO from First";
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController: SecondView];
//show AdView
[self.navigationController presentViewController:nav animated:YES completion:nil];
4- This is it!
5- There is a case, if I'm in FirstViewController and wanted to set a string property in the SecondViewController with the same way, the string won't get the value till you press a some kinda button in SecondViewController, it won't get it like in viewDidLoad for example! don't know why.