I am a relative novice who is teaching himself Objective-C on Xcode to develop some simple iPhone game apps. I have done some reading on this but fear I'm missing something basic and obvious.
I made a simple "Hello, World" and, based on opinions in various forums, I decided to do a Tic Tac Toe. I found a nice video and built a version based on that, which ran fine. However, my own interpretation is already running into trouble.
I'm using Xcode 4.0.2 on Snow Leopard. I chose a View-Based Application template and pulled a large image view onto the layout to hold a PNG called board. I put nine small image views on the large one to hold individual cells for X and O (and created some PNGs for the images). I just attached board.png to the big image view through IB so that works fine.
Next I tried to associate cell 1 with x.png by assigning it to a variable called ximg. This is all set up in the view controller's viewDidLoad method like so -- "ximg = [UIImage imageNamed:#"x.png"];". I then used the code "cell1.image = ximg;" -- also in viewDidLoad. X appeared on the board when I built and ran.
My next step was cell 2. I wanted to use a variable in a custom method this time, so I could change it in the future. I declared a method "- (void)setcell2" (bad camelCase, I know). I put the following method into my view controller implementation file:
-(void)setcell2 {
cell2.image = ximg;
}
I also added the following message to viewDidLoad -- "[self setcell2];"
As you'd guess, I was figuring that when the app loaded, viewDidLoad would send that message to setcell2, which would attach another X in the second box, but this didn't happen.
If someone could give me some idea of what I'm overlooking, I'd be gratified. Example code is appreciated but I can figure that out with time. This is not homework. Thanks for reading!
Most likely you haven't set your cell up properly in Interface Builder. Make sure you have connected the property to the outlet.
Related
I am following a personal learning path for macOS development, learning the basics of C and Objective-C before moving on to Swift (which I already know a bit, but felt the need to learn where all that came from). I am aware there are better, more modern and functional APIs, so please do not suggest learning that or SwiftUI. The point of this question is knowing what is not working in my example.
I closely followed this tutorial, whose source code can be downloaded from here. My code is available here, instead.
The first thing I noticed while following the tutorial is that Xcode (v 13.3.1 on macOS
12.3.1) doesn't add a Collection View Item and a View to the xib's workbench when dragging out a Collection View from the Object Library to the main window. I worked around it by manually adding a Collection View Item and a Custom View to design the UI as the tutorial showed. I triple-checked and connected all outlets as instructed then pressed Cmd-R to build and run. The app crashed, bringing me to main.m at the return NSApplicationMain(argc, argv); line with the following error:
I understand part of this error, but do not know how to "register one item nib or class", while dataSource is not covered in this tutorial.
Comparing with the source code I noticed that an extra outlet was added from the Collection View, connecting its itemPrototype to the CollectionViewItem. I did just that and, this time, Xcode refused to build throwing this error:
Do you know how to make this work? I would also appreciate any and every explanation on the first error.
Thank you for your patience and help.
NSOutlineView changed quite a bit in macOS 10.11 and isn't compatible with the tutorial. NSOutlineView can be used in legacy mode by choosing layout Content Array (Legacy) in IB.
I'm working on an alternate version of a program I already wrote, it's mostly for the sake of understanding a little more.
In x-Code (Objective-C), I have a ViewController that calls out a UIView (GraphicsView) that draws a line from the center to the touch point. This sub-view is smaller than the larger ViewController.
The view controller has a label that outputs the coordinates of the touched point.
So far I was able to get everything working, so that if you touch inside the sub-view you get the line AND the coordinates updated and if you touch outside the sub-view you only get the coordinates updated. I did this using delegates which was a little complicated.
I've been reading some books and I learned about using the extern feature and global variables (which are supposed to be bad practice) and I wanted to try the same app but using global variables.
I declared my externCGPoint in the ViewController.h and imported it on the GraphicsView.m file and in the method touches began I put the definition of myGlobalPoint = touchedpoint; followed by an NSLog that displays the coordinates. So far it works. (However it does not update the coordinates)
However whenever I touch outside the sub-view, into the main view the app crashes with a EXC_BAD_ACCESS message. From what I understand the main View cannot access the global variable if it's declared in another class ?
I've read many there stack overflows about this and I;ve tried it in the methods suggested but I keep getting this error.
i have a subclass of UIViewController, and when it is called from another class the app just freezes - i used the Xcode debugger and figured that when I'm trying to access the class's view property the app freeze. another weird thing is that when i type in the debugger control panel: "po objectOfTheProblematicClass.view" the debugger stops responding.
the code I used was similar to this:
UIStoryboard *sb = [UIStoryboard storyboardWithName:#"Main" bundle:[NSBundle mainBundle]];
WTStickyViewController *stickyVC = [sb instantiateViewControllerWithIdentifier:#"WTStickyViewController"];
stickyVC.sticky = sticky;
// Setup view controller containment:
[self.parentViewController addChildViewController:stickyVC];
self.containerView = self.parentViewController.view;
[self.containerView addSubview:stickyVC.view];
WTStickyViewController is the subclass of UIViewController. the app freezes when it reaches
[self.containerView addSubview:stickyVC.view];
but it's because this is the first time that stickyVC.view is called.
if for example i would put somewhere in the code
UIView *viewForExample = stickyVC.view;
the app would freeze there.
the exact same app works fine when compiled on a device with iOS 8 but has this problem with iOS 9.
if anyone knows why is this happening and if there is a solution it will be great. thank you.
I was having a similar issue and it was absolutely maddening. The CPU went to around 100% in the resource monitor during debug as the app deadlocked. Printing to console or just generally accessing the view controller's view property caused this behavior. Ultimately, what 'fixed' it for me was removing it from the base localization file. I know that doesn't make sense, but I'll elaborate as best as I can.
I'm maintaining a legacy universal app that has 2 'main' storyboards called Main_iPhone and Main_iPad, which as you can probably guess are the loaded dynamically based on what device you're launching on. I noticed that only the iPhone nib view was deadlocking as described, and iPad was loading fine. The only thing I could tell as that the iPhone storyboard had localization enabled while the iPad storyboard had not. So here's the steps I took loosely to remove it from base localization (you may want to do this in a separate branch/sandbox to make sure this works before deleting project references):
Right click the problematic view and/or storyboard in question, show in finder. For me it was inside the Base.lproj folder as expected.
[Re]move the file to a different directory so Xcode can not find the link the project (file goes red in file browser). Press delete to remove the file from the project file's reference from the project itself.
Add the file back at the new location in your repository/project structure so Xcode picks it up as a new file. Ensure all of your references to the file are updated to the new location.
Verify your storyboard/xib file is not localized anymore, clean project, re-run and see if the issue is still there (see image).
You can also just update the file location using the update location button in the file properties view on the right side (see other image).
Don't know if this will fix it, but I thought I'd share what helped me in the chance that it helps others as well.
A bug report was sent to apple and hopefully it will be fixed soon - the problem is indeed with Xcode 7.
If you are encountering a similar problem, it can be solved by doing one of the following:
1) Use Xcode 6.4, at least until apple fixes this bug.
2) Rebuild the problematic view in the storyboard.
I will post the radar link once I got a chance to speak with my manager about it...
I feel i am totally out of my depth here, im very new to objective c but have been asked to design an iphone app as part of my uni course. I designed a sinple quiz before, but I was hoping to design a more advanced quiz game with 3 levels (each level will have a different quiz).
I dont know how to use the UIViews and I have tried a tutorial online to help me code a navigation controller. It allows gives me 3 options to go into subview 1, 2 or 3. All the subviews have the same screen though, with one label and a button.
I have 3 classes so far, RootViewController, BasicNavigationAppDelegate and SubViewOneController.
I really dont understand the code at all, im familiar with Java but this objective c is nothing like it. Could someone maybe take a minute to help out a person in distress and explain if i am doing this right by using the navigation controller to display my levels? When i check the xib interface files i dont see the button or label, or dont know where to add the quiz interface objects!! I really am confused by all this. Could anyone help?
You should search google for sample source code, and see how some of the views can be handled. There are many ways you can handle a view, whether its by a UINavigationController, UITabBarController, etc. If you are new to Objective-C, then your not really going to get an answer to this question that will instruct you on what exactly to do.
Interface Builder + View Controllers
Here's a good one for you: View Controllers Programming Guide
(Apple's) View Controller Reference Guide
Some Code Samples
Getting Started Sample Code
I recommend Head First iPhone Development: A Learner's Guide to Creating Objective-C Applications for the iPhone. Within a few chapters you'll know everything you need to build this app and you'll actually understand what you're doing.
(I don't know the authors or the publisher, I just think it's a great book for quickly getting up to speed.)
for a 3 level quiz, UINavigationController is definitely an option.
if you need to find out how to use a class, in xcode, type its name, then press -alt- and double click the class name, this will bring up a short description, with two icons, one will take you to the header file, and the other to the documentation.
to add elements to the nib/xib files, you will need to open the library window, where you will find labels, buttons etc. to use a button, you will need to define an action in your header file, and hook it up in IB, to be able to interact with UIElements in your code, you want to set up outlets in the header file, and hook them up in IB.
something you need to decide on, is how you are going to present the questions, and will also depend if the answer will be true/false, multiple choice, or text entry.
if you arent familiar with obj-c and xcode, it is probably worth picking up an ebook from someone like http://www.pragprog.com. they have an iPhone one up there by Bill Dudney which is quite good(i believe he now works for apple.)
for the standard slide out transition you could use this.
//you would probably want to call this something like level1NavBarItemWasPushed: instead
- (IBAction)lvl1pushNavBarItem:(id)sender {
//create instance of AnswersViewController class.
AnswersViewController *level1AnswersVC= [[Level1AnswersViewController alloc] init];
//pass it some kind of identifier so it can tell which quiz/question it is dealing with and pull in the answers, so that you can reuse the view
[level1AnswersVC setAnswersObject:<<insert object dictionary here>>];
//push the view controller onto the navigationController's view stack
[self.navigationController pushViewController:level1AnswersVC animated:TRUE];
//pushing it onto the view stack has given it +1 retain, so we can now release it without worrying about it disappearing prematurely.
[level1AnswersVC release];
}
for the page flip transition you could use this.
- (IBAction)lvl1pushNavBarItem:(id)sender {
//create instance of AnswersViewController class.
AnswersViewController *level1AnswersVC= [[Level1AnswersViewController alloc] init];
//pass it some kind of identifier so it can tell which quiz/question it is dealing with and pull in the answers, so that you can reuse the view
[level1AnswersVC setAnswersObject:<<insert object dictionary here>>];
//set the current viewController as the delegate, so that it can call back to us when its done
level1AnswersVC.delegate = self;
//set the modal transition style
level1AnswersVC.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
//show answers as modal view, which has been setup to use the page flip transition.
[self presentModalViewController:level1AnswersVC animated:YES];
//pushing it onto the view stack has given it +1 retain, so we can now release it without worrying about it disappearing prematurely.
[level1AnswersVC release];
}
I'm trying to set a subclassed NSOpenGLView in an unusual way and I am running into some problems. Basically, I am writing a program to perform a bioengineering simulation for my PhD and I need to be able to compile it under both MacOSX and Unix (my machine is a Mac, but the sim will eventually run on a more powerful Unix machine). Since the code will get longer and longer over the next year and a half I'd rather not have to keep track of two completely different versions of the program. So, I'm hoping to be able to compile the ObjectiveC code under Unix by avoiding ObjectiveC-2.0 and keeping the interface optional (it will mostly be there to perform setup before the long simulations and monitor things for the short ones during development).
The current version works well without the interface - the simulation is performed correctly and the program is capable of rendering OpenGL frames and exporting them into image and video files without any problems. Since I am now adding the interface (right now just a simple window with an NSOpenGLView subclass and a "start" button") on top of that (so that I can run the code with an alternate version of main() without it) I have to "wire" OpenGL together in a weird way, since the drawing code is not in the drawRect function, or even anywhere in the subclassed view, but instead in the "basic" program.
What I've done so far is this:
The main program (using an object called "Lattice") performs all the simulations and rendering, correctly outputing images and video to files. This also contains the NSOpenGLContext and calls [renderContext flushBuffer];
A subclass of NSOpenGLView called PottsView contains an instance of a lattice, which is initialized together with the view like this:
- (id)initWithFrame:(NSRect)frame {
if(![super initWithFrame:frame])
return nil;
// code
frameSize.width = WIN_WIDTH;
frameSize.height = WIN_HEIGHT;
[self setFrameSize:frameSize];
init_genrand64(time(0));
latt = [Lattice alloc];
if (SEED_TYPE) {
[latt initWithRandomSites];
} else {
[latt initWithEllipse];
}
[[latt context] makeCurrentContext];
return self;
}
drawRect() is empty.
PottsController is the object instanced in the InterfaceBuilder which connects the start button to the view. The start button simply tells the lattice to run for a number of steps.
Now, pressing start results in the simulation running correctly (i.e. output to files and terminal), but the PottsView is not working correctly. It remains white, but if I cmd+tab parts if it change to sections of a rendered frame. Same if I press Expose (F3).
I've tried several combinations of flushing, setNeedsDisplay, etc, but frankly speaking I'm lost. I haven't done any programming before this April and with this being (as far as I can tell) a completely backwards way of using NSOpenGLView I'm out of ideas. I'm hoping someone can suggest how I can make the current setup work or how to completely rewire the program (while still keeping the interface optional).
It's not clear how you think that you have 'wired' the context and the view together. You can have as many openglContexts as you like - just by drawing into one won't make it's contents show up in a random NSOpenGLView. Apologies if i have missed something.
NSOpenGLView is a fairly simple subclass of NSView that creates the context and pixel format. As you already have those you can do away with NSOpenGLView and use a custom NSView subclass.
You should look at this instruction.. http://developer.apple.com/library/mac/#documentation/GraphicsImaging/Conceptual/OpenGL-MacProgGuide/opengl_drawing/opengl_drawing.html
To draw to the screen you must flush the graphics context from -drawRect:
This will block the main thread while the gpu processes your instructions, this could be a problem if you have many instructions. It also can not happen more than 50fps.
If you are already rendering your frames to files woudn't you be better observing the output directory and drawing the image each time a new one is added, no opengl required?