I have recently started to learn iOS with obj-c from "iOS Programming The Big Nerd Ranch Guide 4th Edition". This edition was released in 2014 and is written with Xcode 5.
I am trying to make a simple app with two buttons and two labels. The labels are connected to two arrays and when a button is pressed an object from the corresponding array is shown in the corresponding text label (it's the Quiz app in chapter 1).
I created the project as a Single View app in Xcode 6, and put all my objects in the view controller class. I have two labels two buttons two arrays and an int to keep track of the object that has to be displayed from the array.
In the book it says that I should initialize the arrays in the initWithNibName method. I tried that but for some reason it never gets called. So I changed the initialization of the arrays to the init method. They initialize fine but when they are called from another method they are nil. Do you have any idea why this is happening?
The second issue I'm having is that I can't manage to get the contents of the storyboard on screen. It says that I'm supposed to make an instance of the ViewController inside the AppDelegate and make it the root window controller but all I get is a white window (or black in case I don't set the color).
UPDATE: I changed the intialization of the arrays from the init method to the viewDidLoad method and now they seem to be working fine. Nothing on the screen though.
It sounds like you're initializing your UIViewController from the app delegate AND a storyboard. If you create a new project in XCode, a "Single view application", you won't have to touch the app delegate at all in order to get something on the screen.
I believe both your problems are related to this, since it sounds like you're seeing an empty UIViewController on the screen (the one you create in the app delegate)
As for the initialization of your array, viewDidLoad is a popular place to do this.
If you are using storyboards, the method initWithNibNameOrNil will not be called. In the BNR book, it teaches you to use XIB files, which do use this method. If you are trying to follow the tutorials, I would suggest using XIB files.
For use of a book, I would suggest downloading whatever version of Xcode is being used for that book -- otherwise you will be running into a lot of confusing problems while learning.
If you would like to download previous version of Xcode, refer to this post:
How to download Xcode DMG or XIP file?
Related
I am having difficulty with something that seems to be trivial. I am following this project https://github.com/eppz/iOS.Blog.UIView_from_Xib and trying to implement the decoupled way of loading a view from a nib file. I was not able to get the desired result in my app (nothing shows up and I get no crashes either) so I did the following:
I took the project from Github https://github.com/eppz/iOS.Blog.UIView_from_Xib
I then proceeded to duplicate the files in the "decoupled" group and name it something trivial like "decoupled2". Basically I am creating a whole new class that stands on its own with its own nib file.
I then changed all of the internal tags and class references. Then I made sure that all of the new references were pointing to this new class.
At this point I added a 6th button to the main VC and made sure to call the right method for my new "decoupled2" class when this 6th button is pressed.
PROBLEM: Everything runs but the view from nib does not show up. Debugging view hierarchy shows nothing. Clicking the 5th button still works, so I didn't break the existing code. Why won't the newly created nib file show up?
This seems rather simple, just duplicate what already works in a project that already works and it will work...or not. What am I missing? Thank you for your help.
I have spent a few days on the problem already. Lots of research but nothing of use so far.
I re-did the task and it worked this time.
Maybe restarting Xcode 8.0 was the key or something else that is under the hood.
I am a developer in training and have been working extensively with storyboard in order to create a fairly simple TabBarController based application. I have assigned tags (values 0-10) to 11 different views in the tab, and am trying to figure out how to make it so that the position of the views in the tabBar are saved when edited by the user. Right now, every time the app is started the, position of the tabs resets, even if changed by the user under the "more" tab automatically added by Xcode. I have started out by adding
func tabBarController(_tabBarController: UITabBarController!, didEndCustomizingViewControllers viewcontrollers: [AnyObject]!, changed: Bool){
if changed{
}
to my app delegate. I am not sure how I would implement such a seemingly simple feature, and would appreciate any help. I am programming in Xcode 6.1.1, on Mac OS 10.10.2, and coding in swift.
Thanks
I have an iPad app that has been running fine until iOS7. This issue seems to be only on ipad 2nd gen models and earlier when iOS7 is installed. Anyway, I've been tearing my hair out trying to figure out where this error is coming from, but have had no luck. The console in xcode (5) reports the following error after I perform a logged in segue:
2013-11-18 11:17:31.768 MyApp[400:60b] *** -[UIToolbar backdropView:willChangeToGraphicsQuality:]: message sent to deallocated instance 0x18ec23e0
I can't lookup the address for more info (image lookup -a 0x18ec23e0) it just returns nothing.
In instruments running zombies, it reports that a message was sent to a UIToolbar like so:
When I inspect the instance, I get the following:
How do I debug this? I have no idea where this call is being made and it seems dependent upon a physical deivce (doesn't happen on the iPad mini or ipad 3/4)
I was struggling with a very similar error, also with a UIToolbar, that I couldn’t figure out until a couple hours ago. I also had to use and try to understand the zombies’ instrument but without any luck.
What I did was to pay a close attention to the call stack that was presented when the Exception Breakpoint was activated as described in the following tutorial:
http://www.raywenderlich.com/10209/my-app-crashed-now-what-part-1
Even though the call stack didn’t point me to the exact code line, I noticed that the app was trying to add a UIToolbar to a ViewController. Turns out that what I was doing was creating a local UIToolbar inside of a method and adding it to the presented UIView. After have modified this behavior, I stopped having the annoying sudden crash. It was difficult for me to find the issue because looking at the code of the ViewController that caused the crash, there was no code that created or used a UIToolbar; however this VC included a custom view that did exactly that, as I explained before.
Have said all of this I recommend you to closely inspect the VC that generates the crash. If you need to create a UIToolbar programmatically I recommend you to declare it as a strong property to maintain the memory reference as long as needed.
I hope this helps you.
I struggled with this for a while today. I had two storyboards, one for login/signup (set as the main storyboard for the project) and another with the rest of the application. The app delegate would detect if a user was logged in and instantiate the root view controller of the other storyboard. The root view controller of the login storyboard is a navigation controller and after after some investigation with instruments I realized there was a UIToolbar being instantiated from the nib. Opening up the storyboard file revealed an off-screen UIToolbar object in the root view controller. I deleted it and I'm not crashing any more.
I should also mention this crash was only occurring when I was using MKMapView.
I'm new to using a mac and iOS development. Today I followed this tutorial on to a how to bind data to a table view by making use of Prototype cells and the Story Board. I've got up to the part of the tutorial where I should be able to run the app so the bound data shows up in the UITableView like this:
My app compiles fine, but as soon as it starts running it hits a runtime error:
[ViewController viewControllers]: unrecognized selector sent to instance
I have tried going through the tutorial several times now. I've followed the tutorial exactly as it says and have even created 3 different projects from scratch to make sure that nothing is going wrong. Can anybody help me fix the error? I've spent hours trying to work out what's going wrong, and I don't want to give up now as iOS development seems so exciting compared to other platforms!
Unrecognized selector means that there is an undefined method being called.
One thing to do is to see if there are any compiler warnings. Does it give you any? Have a look, it may give you a clue what is undefined.
The tutorial refers to ViewController class. It looks like that this class is used briefly at the start of the tutorial but then it is replaced with another class. You may remove this class later on altogether. Check if you wire tab bar controller properly. have you set it to be "an entry point"?
Check the storyboard. Where does an incoming arrow point to? Compare two images below. First has the entry arrow pointing to ViewController (my guess), second - the arrow point to Tab Bar Controller
.
At some point (without the code is hard to tell where) you are getting a reference to a ViewController, treating it as a UITabBarViewController.
viewControllers is a method of UITabBarViewController but you are invoking it on a ViewController.
You probably have something like
UITabBarViewController *tabBarVC = (UITabBarViewController *)[something aMethod];
tabBarVC.viewControllers...
So it compiles fine, but it rightfully crashes at runtime.
Update:
Thanks for all the tips, everyone. The tutorial mentions that a XIB file is provided (which I don't have) so I'm doing something wrong in how I'm creating the the project.
I am following Apple's Core Data Tutorial for iOS. This tutorial has not been updated for ARC—apparently for Xcode 4, since it asks to "create a new project using the Window-Based Application template in the iOS section."
Since that option doesn't exist under Xcode 4.4.1, I looked around Stack Overflow and read that I should create an empty application. As per the tutorial instructions, I created no Storyboard or NIB file.
Other than updating the code for ARC (using strong in place of retain and not implementing the provided dealloc method), I'm confident that the code in my project matches that of the tutorial up to the end of the chapter "The Table View Controller." At this point, the tutorial says I should be able to run the project and get a view.
Instead, I get a blank, black screen.
Maybe my problem is too vague to solve here, but should I perhaps be using a different project template? Which one?
I have only two classes: a RootViewController and an AppDelegate. AppDelegate imports RootViewController and contains a UIWindow property. Again, there is no Storyboard or NIB in the project.
I can provide any code too if there's someplace specific to look.
If you want to check if your setup is correct do the following:
add a background color to your window
self.window.backgroundColor = [UIColor whiteColor];
make sure you tell the window to display itself
[self.window makeKeyAndVisible];
make sure your view controller is the window's rootViewController
self.window.rootViewController = myViewControllerInstance;
Choose Single View Application, and uncheck 'Use storyboards" field. The rest should go the same.