I have put together a simple quote generator, storing the quotes in an array. Following are the quote view controller interface and implementation files:
ViewController.h
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
#property(nonatomic, retain)NSArray *myQuotes;
#property(nonatomic, retain)NSMutableArray *movieQuotes;
#property (nonatomic, retain) IBOutlet UITextView *quote_text;
-(IBAction)quote_btn_touch:(id)sender;
#end
ViewController.m
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize myQuotes;
#synthesize movieQuotes;
#synthesize quote_text;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.myQuotes = [NSArray arrayWithObjects:
#"Live and let live",
#"Don't cry over spilt milk",
#"Always look on the bright side of life",
#"Nobody's perfect",
#"Can't see the woods for the trees",
#"Better to have loved and lost than not loved at all",
#"The early bird catches the worm",
#"As slow as a wet week",
nil];
quote_text = nil;
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
-(IBAction)quote_btn_touch:(id)sender {
// 1 - Get number of rows in array
int array_tot = [self.myQuotes count];
// 2 - Get random index
int index = (arc4random() % array_tot);
// 3 - Get the quote string for the index
NSString *my_quote = [self.myQuotes objectAtIndex:index];
// 4 - Display the quote in the text view
self.quote_text.text = [NSString stringWithFormat:#"Quote:\n\n%#", my_quote];
}
#end
In the xib file, I connected the text view and button to the File's Owner, using quote_text and quote_btn_touch respectively.
Trouble is that when I click on the button, nothing happens. Any idea what I missed?
Thanks in advance!
your setting quote text to nil on viewDidLoad. If you get rid of that your code should work as long as you correctly bound the button to the viewcontroller function
quote_text = nil;
Related
I am trying to update the contents of an NSTextView that is connected to myViewController as a referencing outlet to the Files Owner which is the subclass myViewController.
When I use an IBAction from a button, or use the viewDidLoad method of the controller, I can update the text fine. However, when I try run the method from another class (referred to in this example as anotherViewController), it runs the method, but the textview does not change.
myViewController.h:
#import <Cocoa/Cocoa.h>
#import "anotherViewController.h"
#interface myViewController : NSViewController { }
#property (unsafe_unretained) IBOutlet NSTextView *outText;
#property (weak) IBOutlet NSButton *updateMeButton;
- (void)updateTextView:(NSString *)argText;
- (void)updateTextViewWithoutArg;
#end
myViewController.m:
#import "myViewController.h"
#interface myViewController ()
#end
#implementation myViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.outText.string = #"I work successfully";
}
- (IBAction)updateMeButton:(id)sender {
self.outText.string = #"I am updated text! I also work!";
}
- (void)updateTextView:(NSString *)argText {
self.outText.string = #"I don't make it to the NSTextView :(";
NSLog(#"Should have updated text view");
}
- (void)updateTextViewWithoutArg {
self.outText.string = #"I don't make it to the NSTextView :(";
NSLog(#"Should have updated text view");
}
#end
In anotherViewController.m , which has all the relevant imports, I call this:
myViewController *viewtask = [[myViewController alloc] init];
[viewtask updateTextViewWithoutArg];
Nothing happens. The method runs and logs that it should have updated, but no text updates. I have tried many different approaches, including textstorage and scrollrange methods, they all work the already working sections, but make no difference in the sections not working.
I've also tried just for fun:
myViewController *viewtask;
[viewtask updateTextViewWithoutArg];
Also using the instance variable _outText
Also using [self.outText setString:#"string"];
Also using [_outText setString:#"string"];
Again, they work but only in the already working sections.
This should be simple but isn't logical to me. In swift all I need to do is
self.outText.string = "I update whenever I'm called!"
Views you create in Interface Builder are lazily created, so if you access them before viewDidLoad is called they are nil.
If your case, calling
myViewController *viewtask = [[myViewController alloc] init];
does not cause the views to be created so when you call
[viewtask updateTextViewWithoutArg];
self.outText is nil.
You can see that this is what is happening by updating your code as below:
- (void)updateTextView:(NSString *)argText {
NSAssert(self.outText != nil, #"self.outText must not be nil");
self.outText.string = #"I don't make it to the NSTextView :(";
NSLog(#"Should have updated text view");
}
you should see the assert fire.
I appear to have found a solution by making myViewController a singleton class and using sharedInstance. For this particlar app, myViewController is a debug output window and will never need to be placed in another view.
I won't accept this answer yet, as it's not the best one I'm sure. There may still be a proper solution presented that allows finding the applicable myViewController instance, and modifying the outText property attached to it. Using this singleton makes subclassing tedious as I would have to make a new class for every instance if I wanted to be able to address say 10 View Controllers.
Anyway - the way I've been able to satisfy my simple requirement:
myViewController.h:
#import <Cocoa/Cocoa.h>
#import "anotherViewController.h"
#interface myViewController : NSViewController { }
#property (unsafe_unretained) IBOutlet NSTextView *outText;
#property (weak) IBOutlet NSButton *updateMeButton;
- (void)updateTextView:(NSString *)argText;
- (void)updateTextViewWithoutArg;
+ (id)sharedInstance;
#end
myViewController.m:
#import "myViewController.h"
#interface myViewController ()
#end
#implementation myViewController
static myViewController *sharedInstance = nil;
+ (myViewController *)sharedInstance {
static myViewController *sharedInstance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [[myViewController alloc] init];
});
return sharedInstance;
}
- (void)viewDidLoad {
[super viewDidLoad];
sharedInstance = self;
}
- (void)viewDidUnload {
sharedInstance = nil;
}
- (void)viewDidLoad {
[super viewDidLoad];
self.outText.string = #"I work successfully";
}
- (IBAction)updateMeButton:(id)sender {
sharedInstance.outText.string = #"Button Pressed";
}
- (void)updateTextView:(NSString *)argText {
sharedInstance.outText.string = argText;
}
- (void)updateTextViewWithoutArg {
sharedInstance.outText.string = #"I make it to the TextView now";
}
#end
Now when I use this code from within anotherViewController.m it updates the right instance:
[myViewController.sharedInstance updateTextView:#"Updating with this string"];
Im new to programming with objective C and am working on moving data between View controllers. I am wondering if Bi-directional flow of data (variables) between ViewControllers is possible.
I can move data backwards (to the presentingViewController / sourceViewController) however i cannot move data forward (to the presentedViewController / destinationViewController).
I have made a simple case scenario (involving strings to get a principle of the idea) of this and it involves updating a UItextField on the destinationViewController using a UILabel in the sourceViewController and vice-versa.
I CANNOT update the UITextField using the UILabel, but can update the UILabel using the UITextField.
I have made Logs of different statements to track the variable values however when I switch ViewControllers the variables Data returns to null even if they are marked as strong.
Can you please offer any guidance, its been tearing away at my mind, or am I missing something obvious? I don't get why I keep getting a (null) value (in my NSLog) when I switch ViewControllers.
My sourceViewController / presentingViewController is named "ViewController."
My destinationViewController / presentedViewController is named "Gears2ViewController".
I have attached my code files below:
ViewController.h:
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
#property (strong, nonatomic) IBOutlet UILabel *outputLabel;
- (IBAction)ExitToHere:(UIStoryboardSegue *)sender;
#end
ViewController.m:
#import "ViewController.h"
#import "Gear2ViewController.h"
#interface ViewController ()
- (IBAction)changeItem:(id)sender;
#end
#implementation ViewController
- (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)changeItem:(id)sender {
Gear2ViewController *G2VC=[[Gear2ViewController alloc] init];
G2VC.peterSido=[NSString stringWithFormat:#"%#",self.outputLabel.text];
[self performSegueWithIdentifier:#"toGear2" sender:self];
NSLog(#"ViewController UILabel reads %#",G2VC.peterSido);
}
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
}
- (IBAction)ExitToHere:(UIStoryboardSegue *)sender {
}
#end
Gears2ViewController.h:
#import <UIKit/UIKit.h>
#import "ViewController.h"
#interface Gear2ViewController : UIViewController
#property (strong, nonatomic) NSString *peterSido;
#end
Gears2ViewController.m:
#interface Gear2ViewController ()
#property (strong, nonatomic) IBOutlet UITextField *updatedOutput;
- (IBAction)updateOutput:(id)sender;
#end
#implementation Gear2ViewController
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
NSLog(#"Gears2ViewController ViewDidAppear reads %#",self.peterSido);
}
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(#"Gears2ViewController ViewDidLoad responds %#",self.peterSido);
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)updateOutput:(id)sender {
self.peterSido = self.updatedOutput.text;
((ViewController *)self.presentingViewController).outputLabel.text = self.peterSido;
NSLog(#"Gears2View Controller updating ViewController UILabel reads %#",self.peterSido);
}
#end
NSLog:
2015-06-29 18:52:58.798 testerBeta[21735:645772] Gears2ViewController ViewDidLoad responds (null)
2015-06-29 18:52:58.799 testerBeta[21735:645772] ViewController UILabel reads I like Pie
2015-06-29 18:52:59.317 testerBeta[21735:645772] Gears2ViewController ViewDidAppear reads (null)
2015-06-29 18:53:12.651 testerBeta[21735:645772] Gears2View Controller updating ViewController UILabel reads No I dont
Quite Lengthy but Thanks in Advance!!!
You want to pass the data in prepareForSegue:, like so:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)__unused sender
{
if ([[segue identifier] isEqualToString:#"toGear2"])
{
Gear2ViewController *controller = (Gear2ViewController *)segue.destinationViewController;
controller.peterSido = self.outputLabel.text;
}
}
The reason why is that the segue instantiates the presented view controller for you, and you then set the property of the instantiated view controller which the segue will present.
To pass the data back, you can use an unwind segue, which can get the value from the presented view controller's property.
- (IBAction)unwindFromGear2:(UIStoryboardSegue *)segue
{
Gear2ViewController *controller = (Gear2ViewController *)segue.sourceViewController;
self.outputLabel.text = controller.peterSido;
}
This is the proper way to pass data back and forth via segues. Gear2ViewController shouldn't be setting properties on its presentingViewController.
Update:
The preferred way to test that a property isn't nil is like this:
if (self.peterSido)
{
self.updatedOutput.text = self.peterSido;
}
else // No need for if test here
{
self.updatedOutput.text = #"";
}
That's the long form, but the assignment and if test can be more concisely written as:
self.updatedOutput.text = self.peterSido ?: #"";
When you declare any variable as #property then you need to synthesize it in .m file .
You have declared your outputLabel as #property but you missed to synthesize it in .m file.
When you synthesize any variable then it allows you to get and set the values to it .
Do it it will help you.
Thank you.
I know this has been posted many times but I cannot get it to work, there are no errors in my code (found by Xcode), but what I'm trying to do isn't working.
1- Setup: I have 2 classes, ViewController (UIViewController) and GraphView (UIView)
2- What I am trying to do: I have a BOOL type variable plotPressedVC in ViewController that takes an initial value NO.
Once a button is pressed (this IBAction is located in the ViewController.m file) plotPressedVC = YES. From this, in my GraphView.m file I have an if statement whose condition is met if pressed = YES.
3- My code:
ViewController.h
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController {
#public BOOL plotPressedVC;
}
- (IBAction)plot:(id)sender;
#end
ViewController.h
#import "ViewController.h"
#import "GraphView.h"
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
plotPressedVC = YES;
}
- (IBAction)plot:(id)sender {
plotPressedVC = YES;
GraphView *plotPress = [[GraphView alloc] init];
plotPress.plotPressed = plotPressedVC;
}
#end
GraphView.h
#import <UIKit/UIKit.h>
#interface GraphView : UIView {
BOOL plotPressed;
}
#property (nonatomic) BOOL plotPressed;
#end
GraphView.m
#import "GraphView.h"
#import "ViewController.h"
#implementation GraphView
- (void)drawLineGraphWithContext:(CGContextRef)ctx {
if (plotPressed == YES) {
NSLog(#"yep");
}
// Other code that I want to be in if statement
}
#end
4- Question: What have I done wrong for the if statement's condition to not have been met when pushing the button plot?
EDIT: added NSlog at the end of the plot action, I am getting values 80, -64, -128...
- (IBAction)plot:(id)sender {
plotPressedVC = YES;
NSLog(#"%hhd",plotPressedVC);
GraphView *plotPress = [[GraphView alloc] init];
plotPress.plotPressed = plotPressedVC;
NSLog(#"%hhd",plotPress);
}
New Question: How come plotPress is receiving other numbers than 0 or 1?
It's been asked many times and it usually has the same answer.
The problem is here:
GraphView *plotPress = [[GraphView alloc] init];
plotPress.plotPressed = plotPressedVC;
Here you create a new graph view, set the value on it, and then do nothing else with it. You need to have an outlet or property to the existing graph view and set the plotPressed value on that.
Currently that graph view is never added to another view, and under ARC will be immediately deallocated at the end of the method.
I'm quite new to Cocoa and I am trying to setup a table view backed by an array. I've setup the app delegate as the datasource for the tableview, and implemented NSTableViewDataSource protocol.
When I run the app, I get the following log output:
2012-06-23 18:25:17.312 HelloWorldDesktop[315:903] to do list is nil
2012-06-23 18:25:17.314 HelloWorldDesktop[315:903] Number of rows is 0
2012-06-23 18:25:17.427 HelloWorldDesktop[315:903] App did finish
launching
I thought that when I called reloadData on the tableView it would call numberOfRowsInTableView:(NSTableView *)tableView again to refresh the view, but that doesn't seem to be happening. What have I missed?
My .h and .m listings are below.
AppDelegate.h
#import <Cocoa/Cocoa.h>
#interface AppDelegate : NSObject <NSApplicationDelegate, NSTableViewDataSource>
#property (assign) IBOutlet NSWindow *window;
#property (assign) IBOutlet NSTableView * toDoListTableView;
#property (assign) NSArray * toDoList;
#end
AppDelegate.m
#import "AppDelegate.h"
#implementation AppDelegate
#synthesize window = _window;
#synthesize toDoList;
#synthesize toDoListTableView;
- (void)dealloc
{
[self.toDoList dealloc];
[super dealloc];
}
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
NSLog(#"App did finish launching");
// Insert code here to initialize your application
// toDoList = [[NSMutableArray alloc] init];
toDoList = [[NSMutableArray alloc] initWithObjects:#"item 1", #"item 2", nil];
[self.toDoListTableView reloadData];
// NSLog(#"table view %#", self.toDoListTableView);
}
//check toDoList initialised before we try and return the size
- (NSInteger) numberOfRowsInTableView:(NSTableView *)tableView {
NSInteger count = 0;
if(self.toDoList){
count = [toDoList count];
} else{
NSLog(#"to do list is nil");
}
NSLog(#"Number of rows is %ld", count);
return count;
}
-(id)tableView:(NSTableView *)tableView objectValueForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row {
NSLog(#"in objectValueForTable");
id returnVal = nil;
NSString * colId = [tableColumn identifier];
NSString * item = [self.toDoList objectAtIndex:row];
if([colId isEqualToString:#"toDoCol"]){
returnVal = item;
}
return returnVal;
}
#end
The first thing that I'd check is that you're NSTableView IBOutlet is still set in applicationDidFinishLaunching.
NSLog(#"self.toDoListTableView: %#", self.toDoListTableView)
You should see output like:
<NSTableView: 0x178941a60>
if the outlet is set properly.
If you see 'nil' rather than an object, double check to ensure that your NSTableView is connected to your outlet in the XIB editing mode of Xcode. Here's a documentation link for assistance connecting outlets.
I fixed it - I'd set the appDelegate as the datasource and the delegate for the tableView but ctrl-dragging from the tableView to the appDelegate, but I hadn't ctrl-dragged the other way to actually link up the outlet I'd declared with the table view. It's working now. Thanks for your help though Jeff.
Ok, so I'm a relative noob with Objective-C/iOS programming, so hopefully someone with more knowledge here can help me out.
I have an iPad application using the SplitViewController template (with Core Data). I created another UIViewController (with xib file) called PlayerViewController. This View has several UILabel components on it.
I have a list of players that show up in the RootViewController (UITableView) and when you select a player, I programmatically create a PlayerViewController (in DetailViewController), pass it the NSManagedObject that was passed to the DetailViewController, try to set the text of one of the labels on the PlayerViewController's view, and then add it as a subview to the DetailViewController.
All of this works great except for the setting the text of the label on the PlayerViewController's view. I'm not sure what I'm doing wrong. I have used NSLog to confirm that the NSManagedObject is not nil and that the NSManagedObject property I'm trying to use has the correct text.
I'm at a loss here. Any help would be greatly appreciated. (Code follows):
This method is in the DetailViewController.m file:
- (void)configureView {
// Update the user interface for the detail item.
PlayerViewController *player = [[PlayerViewController alloc] init];
player.player = detailItem;
[self.view addSubview:player.view];
}
This method is called when the user selects an item from the RootViewController (This functionality, calling of configureView, is setup by the template and I haven't changed it).
Setting the player property of the PlayerViewController to object detailItem is handled in the setPlayer method of that class.
- (void)setPlayer:(NSManagedObject *)managedObject {
if (player != managedObject) {
[player release];
player = [managedObject retain];
// Update the view.
[self configureView];
}
}
I then have a configureView method as well in PlayerViewController that sets the text of the label:
- (void)configureView {
nickName.text = [[player valueForKey:#"Nickname"] description];
NSLog(#"Nickname %#", [[player valueForKey:#"Nickname"] description]);
NSLog(#"Nickname %#", nickName.text);
}
Ok, so the first NSLog statement prints the desired value, but the text of the UILabel (called nickName) returns nil.
The following is the full PlayerViewController.h & .m files:
PlayerViewController.h:
#import <UIKit/UIKit.h>
#import <CoreData/CoreData.h>
#interface PlayerViewController : UIViewController {
NSManagedObject *player;
IBOutlet UILabel *nickName;
IBOutlet UILabel *goalCount;
IBOutlet UILabel *assistCount;
IBOutlet UILabel *timeInGame;
}
#property (nonatomic, retain) IBOutlet UILabel *nickName;
#property (nonatomic, retain) IBOutlet UILabel *goalCount;
#property (nonatomic, retain) IBOutlet UILabel *assistCount;
#property (nonatomic, retain) IBOutlet UILabel *timeInGame;
#property (nonatomic, retain) NSManagedObject *player;
#end
PlayerViewController.m:
#import "PlayerViewController.h"
#implementation PlayerViewController
#synthesize nickName, goalCount, assistCount, timeInGame, player;
#pragma mark -
#pragma mark Managing the detail item
/*
When setting the player item, update the view
*/
- (void)setPlayer:(NSManagedObject *)managedObject {
if (player != managedObject) {
[player release];
player = [managedObject retain];
// Update the view.
[self configureView];
}
}
- (void)configureView {
nickName.text = [[player valueForKey:#"Nickname"] description];
NSLog(#"Nickname %#", [[player valueForKey:#"Nickname"] description]);
NSLog(#"Nickname %#", nickName.text);
}
/*
// The designated initializer. Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {
// Custom initialization
}
return self;
}
*/
/*
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
[super viewDidLoad];
}
*/
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Overriden to allow any orientation.
return YES;
}
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload {
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (void)dealloc {
[super dealloc];
}
#end
I'm sure I'm just missing something trivial, but I can't figure it out, and haven't been able to find any answers searching the web.
Thanks for any help!
Ok, so after playing with this for a bit and searching and searching around, I have gotten the answer to my problem. It turns out all the code I had was fine except the location of one statement. My call to configureView in PlayerViewController.m needed to be in viewDidLoad() not in the setPlayer() method. It all works great now.
Change the configureView method to that :
- (void)configureView {
nickName.text = (NSString*)[player valueForKey:#"Nickname"];
}
Yes, better place to call method is
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self configureView];
}
(void)setPlayer:(NSManagedObject *)managedObject called before your nib files loaded.