- (IBAction)button:(id)sender {
struct label.text =
}
Whats the problem?
Why does Xcode say:
"Expected identifier or '('?"
Hopefully you have hooked up your button correctly, are you using storyboards? If you are just drag a button and a label out to the storyboard. Open the assistant editor, it's a button that looks like a tux up in the right hand corner. You need to declare what your items will do. In the assistant open your .h file. Control drag from the label to the .h and select outlet. Call it label it you wish. Then control drag from the button and select action. Call that button if you wish. This is what your .h file should look like.
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *label;
- (IBAction)button:(id)sender;
#end
Then in your .m file you should make it look like.
import "ViewController.h"
#interface ViewController ()
#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)button:(id)sender {
_label.text = #"Hello";
}
#end
I did this and when I touched the button the text changed from label to Hello. You also forgot the colon at the end.
You need to go back to your resources where you learned Objective-C and Cocoa, what you have is wrong in fundamental ways that show you don't understand the language at all
struct label.text =
This looks like just random tokens.
It looks like XCode is simply getting confused because the syntax of your statement is wrong. It looks like the line struct label.text = is trying to define a variable of type struct with the name label.text.
In Objective-C, the dot operator lets you access a method or property of an object. Trying to do this in the name of the variable doesn't make sense.
Related
I watched a video on how to make a button spin in Objective-C. I entered all the code exactly like in video except I got some syntex errors/ "!". I am very new to Xcode and only know some of the basics to javascript. Please help have been trying to figure this out for too long.
This is what I did in ViewController.h:
// ViewController.h
#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
#import <AVFoundation/AVFoundation.h>
This part in the code I get "!", it doesn't seem to like the "()". when I take that part out it's fine but the button doesn't seem to be recognized when it is called later on in ViewController.m. I'll explain what each "!" says to the write of the code where I'm getting each error. to separate it from the code ill put 2 "//" next to it.
#interface ViewController : UIViewController( // ! Method type specifier must start with '-' or '+'
I get 3 error messages on this next line of code.
IBOutlet UIButton *button; //! IBOutlet attribute ignored when parsing type, Expected selector for Objective-C method, and Expected ')'
) //! Expected identifier or '('
- (IBAction)spin:(id)sender;
#end
Now here's what I did in ViewController.m
// ViewController.m
#import "ViewController.h"
#interface ViewController ()
#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)spin:(id)sender {
CABasicAnimation *fullRotation = [CABasicAnimation
animationWithKeyPath:#"transform.rotate" ];
fullRotation.fromValue = [NSNumber numberWithFloat:0];
fullRotation.toValue = [NSNumber numberWithFloat:((360*M_PI)/180)];
fullRotation.duration = 2.0;
fullRotation.repeatCount = 300;
in this part of the code I get the "!" again no matter what I do to change it
[button.layer addAnimation:fullRotation forKey:#"360"]; //! Use of undeclared identifier 'button'
}
#end
UIViewController( should not have the ( on the end.
just use:
// ViewController.h
#interface ViewController : UIViewController
#property(nonatomic, weak) UIButton *button;
- (IBAction)spin:(id)sender;
It's recommended to use #property since it generates getter/setter and you can set weak reference.
and in the implementation file add self.
[self.button.layer addAnimation:fullRotation forKey:#"360"]
I'm using Xcode to write an app in objective c. I am trying to pass data from a container view controller to the parent view controller using delegation. I have successfully passed the data to the parent view controller, but all of the documentation sets what I have sent to the .h header file in the .m implementation file using viewDidLoad or viewDidAppear. I was wondering, since the view is already present, if there is a way to detect that data has been changed in a view and automatically run a method or code to update the view with the new information. Something along the idea of didReceiveNewData or didEditExistingValues (of course those arent real methods). Thank you for your help!
Edit: What I have done so far:
I want to pass the data from MainFeedTableViewController to MainFeedViewController (The first is in a container inside of the second). I want to set the title of the custom navigation bar in MainFeedViewController to something described in the MainFeedTableViewController.
In the MainFeedTableViewController.m (the view sending data) I have:
#import "MainFeedTableViewController.h"
#import "FeedViewController.h"
#interface MainFeedTableViewController ()
#end
#implementation MainFeedTableViewController
- (IBAction)swipeLeftDetected:(UIGestureRecognizer *)sender {
UIStoryboard *mc = self.storyboard;
FeedViewController *fv = [mc instantiateViewControllerWithIdentifier:#"FeedViewController"];
fv.navigationBarTitleToSet = #"HOPING TO SET TITLE TO THIS";
[self performSegueWithIdentifier:#"MainToLocalFeed" sender:self];
}
and some other unrelated stuff..
In the MainFeedTableViewController.h I have:
#import <UIKit/UIKit.h>
#interface MainFeedTableViewController : UITableViewController
#end
In the MainFeedViewController.m (the one receiving the data) I have:
#import "FeedViewController.h"
#interface FeedViewController () <UINavigationBarDelegate>
#property (weak, nonatomic) IBOutlet UINavigationBar *navigationBar;
#end
#implementation FeedViewController
- (void)viewDidLoad {
[super viewDidLoad];
}
- (void)setNavigationBarTitle:(NSString *)navigationBarTitle{
self.navigationItem.title = navigationBarTitle;
}
And in the MainFeedViewController.h I have:
#import <UIKit/UIKit.h>
#interface FeedViewController : UIViewController
#property NSString *navigationBarTitleToSet;
#end
I want to run the setNavigationBarTitle method with either data from the .h (navigationBarTitleToSet) or just from the sending view controller, if possible to run a method with delegation. Thanks a ton and I hope this is possible :)
It turns out I needed to add a second navigation bar to account for the container view, allowing me to navigate around the current stack with the parentViewController method and then navigationItem.title. For anyone who happens to find this with a container, make sure you add one immediately after the embed segue. I'm still not sure if you can use methods through delegation, but I can't ponder any situations where it would be necessary anymore, due to viewDidLoad. Thanks to #Tander for the help!
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).
For some reason, i'm not able to change or add text in my UITextView from code.
I have made Outlet and connected (All in IB) - nothing happens.
Even tried to add -setNeedsDisplay
Do i need to set some property ? - This i driving me nuts....
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController <UITextViewDelegate> {
UITextView *textInfoView;
}
#property (nonatomic, retain) IBOutlet UITextView *textInfoView;
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
textInfoView.text = #"Test";
}
-(void)viewDidAppear:(BOOL)animated{
textInfoView.text = #"Test";
textInfoView.text = [textInfoView.text stringByAppendingString:#"Line2"];
[textInfoView setNeedsDisplay];
It seems, really strange that this code doesn't update the text inside the UITextView. I have tried and it works for me ... I think that you don't have correctly linked the Outlet in interface builder, or you don't have associated your view controller to your view ...
UPS - Got it...
Forgot to #synthesize...
For some reason i did not get warning or "setter error" in Xcode 4.4, maybe it's a version bug ?
I'm trying to create a simple Quiz app (I'm a beginner), when I launch the app I want a UILabel to show the first question (of an array of questions). I'm having some trouble with setting the initial value.
I've done a couple of attempts, whiteout success. I my QuizAppDelegate.h file I declare my UILabel like this:
IBOutlet UILabel * questionField;
In my main .m file I have tried the following:
- (id)init {
[super init];
questions = [[NSMutableArray alloc] init];
// Not working
questionField = [[UILabel alloc] init];
[questionField setText:#"Hello"];
// Working
NSLog(#"Hello");
[self defaultQuestions];
// [self showQuestion];
return self;
}
Another thing I have tried is the following in QuizAppDelegate:
#property (nonatomic, retain) IBOutlet UILabel *questionField;
- (void)changeTitle:(NSString *)toName;
And in the .m file:
#synthesize questionField;
- (id)init {
[super init];
questions = [[NSMutableArray alloc] init];
// Not working
[self changeTitle:#"Hello"];
// Working
NSLog(#"Hello");
[self defaultQuestions];
// [self showQuestion];
return self;
}
-(void)changeTitle:(NSString *)toName {
[questionField setText:toName];
}
Any tips on how to solve this would be great!
// Anders
Hopefully you're not actually putting code into main.m. On iOS, you rarely modify that file.
Since you're doing everything in the AppDelegate, let's keep it there (as opposed to creating a new UIViewController). Let's start with the basics.
Adding the Label as an instance variable
You're doing this correctly—inside the curly braces of the .h file, put the line
IBOutlet UILabel * questionField;
Then, declare the corresponding property, and make sure to synthesize it in the .m file.
#property (nonatomic, retain) IBOutlet UILabel *questionField;
#synthesize questionField // in the .m file
Adding the UILabel in Interface Builder
Open up MainWindow.xib. Drag a UILabel from the Library to the Window that represents your app's window. Then Control-Drag from the AppDelegate object (the third icon on the left in Xcode 4; it'll be labelled in the Document window in IB 3). You'll see a little black window come up—select the option called questionField to make the connection.
See this link for screenshots and how to make connections in IB. The same applies in Xcode 4.
Changing the text
You don't need a separate method to change the text—just modify the label's text property.
Pick a method that'll be called when the app launches (applicationDidFinishLaunching:WithOptions: is a good place to do it in), and put the following code:
questionField.text = #"Hello";
And that's it!
Code
QuizAppDelegate.h
#import <UIKit/UIKit.h>
#interface QuizAppDelegate : NSObject <UIApplicationDelegate> {
IBOutlet UILabel *questionField;
}
#property (nonatomic, retain) IBOutlet UIWindow *window;
#property (nonatomic, retain) IBOutlet UILabel *questionField;
#end
QuizAppDelegate.m
#import "QuizAppDelegate.h"
#implementation QuizAppDelegate
#synthesize window=_window;
#synthesize questionField;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Override point for customization after application launch.
// Add the tab bar controller's current view as a subview of the window
[self.window addSubview:self.questionField];
[self.window makeKeyAndVisible];
self.questionField.text = #"Hello";
return YES;
}
- (void)dealloc
{
[_window release];
[questionField release];
[super dealloc];
}
#end
If you're creating the label programmatically, then you have to add the label to the view:
[self.view addSubview:questionField];
This assumes that you have a ViewController. If not, and you're doing this directly in the AppDelegate (a very bad idea, by the way), then do
[self.window addSubview:questionField];
If you're creating it in the IB, make sure you set up the connections.
You should not both add the UILabel in the IB and instantiate it programmatically. Only call alloc if you are creating it programmatically. Otherwise, if using the IB, skip that part. You created it already with the xib.
I suspect that you have either not created your Interface Builder layout properly - either you have missed the control out all together or more likely you have not connected that control to the questionField outlet in yout header file.
You need to drag a UILabel view into the main view and then connect it to the correct line in your header file.
You shouldn't be using your main.m like that at all. In fact, you should almost certainly never do anything with it. Try creating a UIViewController subclass and practicing your quiz with that. (Add the UILabel to the IB file and then connect the outlet.) Perhaps use the View-Based Application template while you are practicing.
This is a good answer:
"You're doing this correctly—inside the curly braces of the .h file, put the line
IBOutlet UILabel * questionField;"
I was trying to change the value of mylabel.text and the screen didn't update the label with this.value. I included the {IBOutlet UILabel * mylabel} and it works like a charm!
So this answer is valid to change the text of a label programmatically!
Thanks