I have an custom UIVIewController that is the base class for other controllers and has an instance of a custom UIView variable that is accessed by inherited the classes.
BaseViewController.h
#interface BaseViewController : UIViewController {
UIView *_vwHeader;
}
#end
BaseViewController.m
#import "BaseViewController.h"
#implementation BaseViewController
-(void)loadView {
[super loadView];
_vwHeader = [[UIView alloc] init];
}
#end
CustomViewController.h
#import "BaseViewController.h"
#interface CustomViewController : BaseViewController
#end
CustomViewController.m
#import "CustomViewController.h"
#implementation CustomViewController
- (void)loadView
{
[super loadView];
[_vwHeader setHidden:NO];
}
#end
The problem is that when I am running it on the simulator everything works perfectly fine, but when I change to the device I have an error on the [_vwHeader setHidden:NO]; line which says: '_vwHeader' undeclared (first use in this function)
I already tried to do:
Comment this line of code, but then it gives me an error in another class using a variable from the base class the same way (It only returns one error at a time), so it seems that it is not an specific error in the view or the controller class as the error occurs in other clases with different types, such as UIView and NSObject types
Change target compiler configuration, such as: architectures (all of them), base sdk (all above 4.0) didn't change anything
What seem to solve the problem, but not completely
Creating a property for _vwHeader and accessing it by self._vwHeader or super._vwHeader seems to work, but having to create a property just to access a variable does not make me confortable, specially because I would have to do it for all variables in the same situation inside my project.
changed C/C++ compiler version: using Apple LLVM Compiler 2.1 makes the compilation error goes away, but gives a bunch of other problems with other libraries being used in the project. So, it is not a definitive solution, but might be a clue of what the problem is.
EDIT:
I tried to create another variable that is not a pointer, a BOOL instead of the UIView * and then used it in the inherited class: the problem also occurs
EDIT (2):
I have no properties whatsoever in any of my classes and I still get the error.
I just added the properties for test porpouses, to see if a property in a parent class caused the same behaviour, and apparently it doesn't.
Something that is also weird is that when I get the error in the variable, I checked with my intellisense and it finds it...
In order to refer to an instance variable within any object other than self, including super, you must use the structure pointer operator (->). The default scope of an instance variable is protected, which means it can only be accessed within the class it is defined in or a subclass of that class. Since CustomViewController is a subclass of BaseViewController, this scope is sufficient to access the variable using self->_vwHeader, but if the second class you were trying to do this from is not a subclass you will also need to change the scope to either #public or #package.
In summary, change your method call to:
[self->_vwHeader setHidden:NO];
and it should work for any subclasses of the base view controller.
Do a clean and build, and also make sure you are not specifying a specific framework search path in the build settings. If you leave it empty you should get the correct libraries.
well I don't know, should work.
BaseViewController.h
#interface BaseViewController : UIViewController {
UIView *_vwHeader;
}
#property(nonatomic,retain)UIView *_vwHeader;
#end
BaseViewController.m
#synthesize _vwHeader;
CustomViewController.m
#import "CustomViewController.h"
#implementation CustomViewController
- (void)loadView
{
[super loadView];
[self._vwHeader setHidden:NO];
}
#end
I faced similar problem as you. In my case the reason was (strangely!) wrong synthesization of properties in subclass.
Example:
In .h file of subclass you have following declaration
BOOL _flag;
...
#property (nonatomic, assign) BOOL flag;
while in you synthesize the property in the wrong way:
#synthesize flag;
instead of
#synthesize flag = _flag;
Strangely, the compiler does not complain about the wrong synthesization (the properties even work fine!), but raises an error, when I try to access protected fields declared in base class.
Detailed explanation
Here is what my code look like
I have base class (excerpt):
#interface BaseEditionModalController : NSObject
{
DataContext *_dataContext;
}
And I have subclass of it (excerpt):
#interface LocationModalController : BaseEditionModalController
{
MCLocation *_readLocation;
LocationCommModel *_oldLocationCommModel;
}
//This is MCLocation for reading only - from the main application context
#property (nonatomic, retain) MCLocation *readLocation;
#property (nonatomic, retain) LocationCommModel *oldLocationCommModel;
#end
And in the LocationModalController.m I have following wrong declarations:
#implementation LocationModalController
#synthesize readLocation;
#synthesize oldLocationCommModel;
Trying to access _dataContext in LocationModalController produced the error that _dataContext is undeclared.
Changing the synthesization of properties to:
#implementation LocationModalController
#synthesize readLocation = _readLocation;
#synthesize oldLocationCommModel = _oldLocationCommModel;
MAGICALLY SOLVES THE PROBLEM!
Regards
I just stumble upon your method declaration
-(void)loadView { ... }
In a view the first point you can rely that everything is fully initialized is after -(void)viewDidLoad was called. Maybe your code works on the simulator because your Mac is fast enough to cope this speed issue - but your mobile device isn't.
Maybe try this coding:
Your BaseViewController.h file:
#interface BaseViewController : UIViewController {
UIView *_vwHeader;
}
#end
Your BaseViewController.m file:
#import "BaseViewController.h"
#implementation BaseViewController
-(void)viewDidLoad {
[super viewDidLoad];
_vwHeader = [[UIView alloc] init];
}
Your CustomViewController.h file:
#interface CustomViewController : BaseViewController {
}
#end
Your CustomViewController.m file:
#import "CustomViewController.h"
-(void)viewDidLoad {
[super viewDidLoad];
[_vwHeader setHidden:NO];
}
Now your CustomViewController can rely on every instance variable in BaseViewController is correctly instantiated.
The error says that _vwHeader undeclared.
So try by modifying the code in:
CustomViewController.m
#import "CustomViewController.h"
#implementation CustomViewController
- (void)loadView
{
[super loadView];
if(!_vwHeader)
{
_vwHeader = [[UIView alloc]init];
}
[_vwHeader setHidden:NO];
}
#end
It is possible that when you compile for target and for simulation the data members are either protected or private. Probably for target are private by default and this seems to cause the problem. Try out playing with the #private and #protected keywords.
However, I strongly suggest that you use properties even between your super/sub-classes. Having a complex structure is a bit hard to debug. Setting up a property will transfer the access to the data through the getter/setter methods (a breakpoint on #synthesize also works) and you will be able to see in the call stack who is accessing what.
Especially, the syntax #synthesize propertyName = prefixDataNameSufix; allows you to easily adjust your class interface style without having to modify your coding habits.
I had the exact same problem and it turns out that I did not remove an unused iVar/property in the SUBCLASS. Let's call it session. I removed _session from the iVar but I forgot to remove it from the properties, then in the .m file I had this synthesize session = _session. Once I removed them all, I can compile for iOS device without problems.
If you think your superclass is fine, look into your subclass, check your iVars and properties and synthesize section in the .m file
I had this exact problem.
In my case, I was relying on ivar synthesis of a property. That is, I did NOT declare UITextView *textView_, but I did #synthesize textView = textView_;
This builds fine on my iOS Simulator. However, my iOS device build fails, regardless of whether I use llvm or gcc.
When I add the declaration back to my interface:
#interface MyTableViewController : BaseTableViewController {
#private
UITextView *textView_; // this line is important!
}
Everything works fine!
See the answer from tc above. This is a bug in the compiler shipped with sdk 4.2.
Specifically I have seen the same error and if on the same machine I have sdk 4.2 and sdk 4.3 installed the error disappears (even if I compile for 4.2).
If anyone is having this issue after upgrading their tools and devices to iOS10, I had it and found that declaring them as weak, nonatomic in the .h file was the issue. I had never encountered this when doing so before but after removing (weak, nonatomic) from the property declaration, everything worked fine again.
Related
Since xcode 4.4 you don't need to #synthesize properties anymore (see here), the compiler does it for you. So, why does the compiler complain
use of the undeclared identifier _aVar
in my viewDidLoad method of ViewControllerSubclass:
#interface ViewController : UIViewController
#property (assign, nonatomic) int aVar;
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.aVar = 5;
NSLog(#"Super value: %d", _aVar);
}
#end
#interface ViewControllerSubclass : ViewController
#end
#interface ViewControllerSubclass ()
#property (assign, nonatomic) int aVar;
#end
#implementation ViewControllerSubclass
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(#"Subclass value: %d", _aVar);
}
#end
If I move everything to the one file instead of 4 separate files for the respective interfaces and implementations, the compiler instead complains that _aVar is private. But _aVar should have been automatically synthesized in my ViewControllerSubclass.
Still keeping everything in 1 file, if I move the initial property declaration to a class extension:
#interface ViewController ()
#property (assign, nonatomic) int aVar;
#end
The build still fails saying that _aVar is private.
If I go back to the 4 file setup for the respective interfaces and implementations xcode builds without even a warning.
If I then run the code:
[[[ViewControllerSubclass alloc] init] view];
the log statements in the above examples print out the following:
Super value: 0
Subclass value: 5
It makes sense that NSLog(#"Super value: %d", _aVar); produced a result of 0 because this variable is supposed to be private to the superclass. But then, why does NSLog(#"Subclass value: %d", _aVar); produce a result of 5??
This is all very odd.
You are confusing several different issues, and I'm somewhat confused when you talk about jumping between files and you don't specify where your errors are happening.
Anyway, there is the issue of instance variable visibility. If you declare your iVars within the interface scope, they are, by default, protected.
#interface Foo : NSObject {
int protectedInt;
#private
int privateInt;
#public
int publicInt;
}
#end
When you synthesize iVars, the instance variables themselves are private, unless you explicitly specify them.
Methods will always fire on the most derived implementation.
Now, when you call this...
[[[ViewControllerSubclass alloc] init] view];
You will allocate a subclass, initialize, and cause the view to be loaded. This code will execute...
#implementation ViewControllerSubclass
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(#"Subclass value: %d", _aVar);
}
#end
The first thing it does is call the base class implementation...
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.aVar = 5;
NSLog(#"Super value: %d", _aVar);
}
#end
Of course, it calls super, but that part's not important here. The next line assigns 5 to self.iVar. But, which iVar? It calls the property setter method on this object. What type is this instance? It's a ViewControllerSubclass. Since you have given both your base class and its subclass the same name (and declared the property as part of the class extension), they each have their own private-scope instance variable .
However, a method is called on the most derived implementation. Thus, self.iVar will set the instance variable of the subclass. The instance variable for the base class remains unchanged.
When you NSLog the value, you are accessing the private instance variable of the base class, which has not been changed.
Now, after the base class viewDidLoad finishes, we get the code running for the subclass. It logs the value of its private instance variable, which was changed as a result of the base class calling the property setter. So, it will now print it's value, which is 5.
When you make the superclass declaration public, the compiler won't attempt to re-synthesize the property; it assumes that's been taken care of in the superclass. Thus, _aVar is not in scope anywhere in the subclass. It's private anyway, so even when you put them all in the same file that's why you see those errors.
However when you make the superclass property declaration inside the class extension, the compiler will auto-synthesize the property for both the superclass and the subclass. This ends up with both classes having private instance variables _aVar (with two distinct addresses). However, when the superclass viewDidLoad method sets the property, the method invokes the subclass's accessors, which set the value of the subclass's private _aVar variable, and not the superclass's. So that explains why you see the superclass value not changing.
Hope this helps!
I just tested your setup and could replicate your error. I came to the following conclusion:
You need to declare your #property in a .h file. If you want a private variable, declare it in .m in the category #interface (the one with the parentheses).
I got SO questions also same as this and I tried with solution but still its not working for mine so asked this again.
This is my VCWithProtocol.h
#protocol mydemoDelegate
#optional
-(void)demoDelegateMethodWithSuccess:(BOOL)yesOrNo;
#end
#interface VCWithProtocol : UIViewController
{
id<mydemoDelegate>mydelegate;
}
#property (nonatomic,assign)id<mydemoDelegate>mydelegate;
VCWithProtocol.m
`#synthesize mydelegate`
This is my class where I am trying to use my Delegate
#class VCWithProtocol;
#interface VCTOUseDelegate : UIViewController <mydemoDelegate> //here is where it shows error with cannot find protocol declaration
VCTOUseDelegate.m
VCWithProtocol *obj = [[VCWithProtocol alloc] init];
obj.mydelegate = self;
I tried with Importing VCWithProtocol but not working as well
Instead of #class VCWithProtocol; write #import VCWithProtocol.h
And some good practice Use capital letter for first character of any class name and protocol.
e.g. MyDemoDelegate and avoid retaining delegate use
#property (nonatomic,assign)id<mydemoDelegate>mydelegate;
Synthesize your mydelegate, and call
[self mydelegate];
You need to add #import "VCWithProtocol.h" to the top of your .m file.
#property (nonatomic,**weak**)id<mydemoDelegate>mydelegate;
delegate always needs weak link
I don't like warnings lying around and this one has been bothering me. Any ideas on what I am doing wrong? I have tons of properties using this same approach and none of them are giving me warnings. Why doesn't Xcode recognize this one?
While the app works as expected, Xcode gives me the following compile time warning:
'OnlinePeerBrowser' may not respond to '-setMyParent:'
My property declaration in OnlinePeerBrowser.h
#import "WelcomeViewController.h"
#interface OnlinePeerBrowser : UIViewController <UITableViewDelegate, UITableViewDataSource, NSNetServiceBrowserDelegate> {
WelcomeViewController *_myParent;
}
#property (nonatomic, assign) WelcomeViewController *myParent;
OnlinePeerBrowser.m has
#synthesize myParent=_myParent;
I am getting the warning on setMyParent in WelcomeViewController.m here...
#import "WelcomeViewController.h"
#import "OnlinePeerBrowser.h"
#implementation WelcomeViewController
- (void)peerPickerController:(GKPeerPickerController *)picker didSelectConnectionType:(GKPeerPickerConnectionType)type {
...
OnlinePeerBrowser *controller = [[OnlinePeerBrowser alloc]
initWithNibName:#"OnlinePeerBrowser" bundle:nil];
[controller setMyParent:self];
}
Also, what is weird is that I can not use the dot syntax here either.
controller.myParent = self;
gives me the following error:
/Users/vesselhead/Development/iPhone/DJBox/WelcomeViewController.m:254: error: request for member 'myParent' in something not a structure or union
I feel like I must be missing something very simple.
The code you've posted looks correct. That means that the compiler is pulling in another declaration of the OnlinePeerBrowser class from somewhere.
Check for circular imports.
Check if you have multiple copies of the OnlinePeerBrowser.h file.
Add the line #warning Testing to your OnlinePeerBrowser.h file. That warning should then appear in the log when you compile. If that warning doesn't appear then that file isn't being picked up by the compiler.
If it's a circular import then don't import "WelcomeViewController.h" in "OnlinePeerBrowser.h". Instead, use a forward declaration in OnlinePeerBrowser.h, e.g. #class WelcomeViewController , and import "WelcomeViewController.h" in OnlinePeerBrowser.m
Sometimes Circular Imports create an issue with the compiler.
Instead of using
#import "WelcomeViewController.h"
in OnlinePeerBrowser.h move that line to the OnlinePeerBrowser.m and add
#class WelcomeViewController
to the OnlinePeerBrowser.h
this will allow you to set the Class of myParent and _myParent to WelcomeViewController and not have the Circular Import.
Alternatively:
you may want to use a #protocol that the WeclomeViewController would have to adhere to. Then you would only have to import the Classes in one direction.
the implementation for a Protocol property would be as Follows
//#import "WelcomeViewController.h"
#protocol OnlinePeerBrowserParent <NSObject>
#required
- (NSString*) informationFromParent;
#end
#interface OnlinePeerBrowser : UIViewController <UITableViewDelegate, UITableViewDataSource, NSNetServiceBrowserDelegate> {
id<OnlinePeerBrowserParent> _myParent;
}
#property (nonatomic, assign) id<OnlinePeerBrowserParent> myParent;
notice the Protocol is on the OnlinePeerBrowser.h so you can import the OnlinePeerBrowser.h and get the Protocol by default.
finally you implement the Protocol in the WelcomeViewController as so
#implementation WelcomeViewController<OnlinePeerBrowserParent>
- (NSString*) informationFromParent
{
return #"My Parental Info";
}
...... etc
I am in the process of cleaning my code and testing for bugs, when I came across this build error: ['xmlEntity' is not an Objective-C class name or alias]. Here is a shorten version of my class .h file.
#interface PMXMLParser : NSXMLParser {
NSMutableDictionary *xmlEntity;
NSMutableDictionary *collectionDict;
}
#property (nonatomic, retain) NSMutableDictionary *xmlEntity;
#property (nonatomic, retain) NSMutableDictionary *collectionDict;
#end
Here is the .m file.
#implementation PMXMLParser
#synthesize xmlEntity, collectionDict
- (void) dealloc
{
// this builds correctly, with no issues.
[collectionDict release];
// 1. This works
//self.xmlEntity = nil;
// 2. This causes the build error: 'xmlEntity' is not an Objective-C class name or alias
//[xmlEntity release];
[super dealloc];
}
#end
Now to me these example 1 and 2 do the same thing, just with a little bit more work is done for number 1.
Does anyone know why I am getting this build error for number 2?
Edit: 07/30/2010 - The code presented here will compile correctly, this is just a shorten version of my whole class. But my current class does not compile. I will post the whole class later when I taken out private code.
Thanks.
Is that really your implementation? You need to have a separate #implementation section in a ".m" source file, and you need to #synthesize those properties before you can use them. Also, your dealloc function needs to go in the #implementation section. But, those issues aside, if you can use the expression self.xmlEntity but not xmlEntity it means there is a scoping issue (probably because you aren't in the #implementation section) which can be fixed by using:
[self.xmlEntity release];
That said, I would address the aforementioned issues properly.
I found out that the program I was working on included the framework libxml2.dylib. Which had an structure called xmlEntity. What lead me to the problem was the syntax color for the item xmlEntity, which was a light purple color.
So I'm still very new to this whole objective C think and I ran into a problem I'm not sure the root cause for.
My h file looks basically like this :
#interface DrinkDetailViewController : UIViewController<UITextFieldDelegate>
{
UITextField* nameTextField;
UITextField* activeView;
}
#property (nonatomic,retain) IBOutlet UITextField* nameTextField;
In my m file i'm implementing the delegate function :
-(BOOL) textFieldShouldBeginEditing:(UITextField*) textField
{
activeView = textField;
return YES;
}
The thing is that if i'm declaring activeView to be a property as well (meaning adding property, synthesize and the all deal), then when i'm leaving the view (it's a navigation based project) my app crashes. However, if I live it as a non property everything seems to work fine. Why is that ???
because it's a property you need to call it this way:
self.activeView = textField;
That way the correct memory management rules will be applied and also the KVO notifications will be done for you.
are you synthesing activeView in your implementation file:
#synthesize activeView;