In the following example, is the line NSObject *_propertyName; required?
.h
#interface ClassName
{
NSObject *_propertyName;
}
#property (nonatomic, retain) NSObject *propertyName;
#end
.m
#implementation ClassName
#synthesize propertyName = _propertyName;
#end
I find that if I exclude NSObject *_propertyName; but keep #synthesize propertyName = _propertyName; everything works. Here's an example of what I'm talking about:
.h
#interface ClassName
#property (nonatomic, retain) NSObject *propertyName;
#end
.m
#implementation ClassName
#synthesize propertyName = _propertyName;
#end
I've tested and seen that the property still works. I nearly always see code that includes the line NSObject *_propertyName;. Is there something I'm missing here?
You're not missing anything. Starting with the newer runtimes (newer iOS Simulator, x86_64 and ARM) you no longer need to manually declare an ivar. Prior to that on i386 and PPC you had to manually declare your ivars.
Related
I am getting new warning on my old OSX app. I am using OSX 10.10 and I am not quite sure where the problem is. Can someone help?
The actual warning is Property type 'id is incompatible with type id inherited from NSTextField
#import <Cocoa/Cocoa.h>
#import "HyperlinkTextFieldDelegate.h"
#interface HyperlinkTextField : NSTextField <NSTextFieldDelegate>
#property (assign) id <HyperlinkTextFieldDelegate> delegate; <--- warning showing up here
#end
The main implementation is
#interface HyperlinkTextField ()
#property (nonatomic, readonly) NSArray *hyperlinkInfos;
#property (nonatomic, readonly) NSTextView *textView;
- (void)_resetHyperlinkCursorRects;
#end
#define kHyperlinkInfoCharacterRangeKey #"range"
#define kHyperlinkInfoURLKey #"url"
#define kHyperlinkInfoRectKey #"rect"
#implementation HyperlinkTextField
#synthesize delegate;
And the delegate file is
#import <Foundation/Foundation.h>
#protocol HyperlinkTextFieldDelegate <NSObject>
- (void) barLinkClicked: (id) sender;
#end
NSTextField already has a delegate property, and it is typed as id<NSTextFieldDelegate>. Thus, your HyperinkTextField, which is a subclass of NSTextField, inherits this property, just as the error message clearly tells you. You cannot override this inherited property and type it as id<HyperlinkTextFieldDelegate> where that is a different type.
So I'm trying to access the property isPortClosed(BOOL) in SerialPortController and its giving me an error, I'm kinda new to objective-c. I feel like this should work as I've got a reference to the class with *port. Here is a link to the project.
Error messages: ~/GroundStation/GroundStation/ViewController.m:16:22: Property 'isPortClosed' not found on object of type 'SerialPortController *'
#import <Cocoa/Cocoa.h>
#import "SceneView.h"
#import "SerialPortController.h"
#interface ViewController : NSViewController
#property (strong) IBOutlet SerialPortController *port;
#property (weak) IBOutlet SceneView *accelSceneView;
#end
#import "ViewController.h"
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
while(!self.port.isPortClosed) {
}
}
- (void)setRepresentedObject:(id)representedObject {
[super setRepresentedObject:representedObject];
// Update the view, if already loaded.
}
#end
SerialPortController.h class
#import <Foundation/Foundation.h>
#import <ORSSerial/ORSSerial.h>
#interface SerialPortController : NSObject <ORSSerialPortDelegate>
#property (nonatomic, strong) ORSSerialPort *serial;
#property (nonatomic, strong) ORSSerialPortManager *serialPortManager;
#property (nonatomic) NSInteger xAngle;
#property (nonatomic) NSInteger yAngle;
#property (nonatomic) NSInteger zAngle;
#property (nonatomic) NSString *stringBuffer;
#property (nonatomic) BOOL isPortClosed;
#end
From the downloaded project I see that you have two SerialPortController class definitions (one at the root directory, and one in /GroundStation/), and the latter doesn't have any public properties. You should have only one SerialPortController class definition linked in your project (the one with the public properties).
I've just starting out with obj-c and I created 2 files, a .h and a .m file. The .h file is..
#import <Foundation/Foundation.h>
#interface CardUnit : NSObject
{
#private
NSString *_name;
NSString *_gold;
}
#property (nonatomic, assign) NSString *name;
#property (nonatomic, assign) NSString *gold;
#end
and the .m file is
#import "CardUnit.h"
#implementation CardUnit
#synthesize gold = _gold;
#synthesize name = _name;
#end
But it's giving me 2 errors on the #synthesize lines, which are...
"Existing ivar "_gold" for property gold with assign attribute must be __unsafe retained" and the same for name.
From the error i see you are using ARC, Automatic Reference Counting .
Basically you can get rid of all the #synthesize statements and even the private declarations of the ivar's name and gold is not necessary.
All you need is the CardUnit.h to be like this :
#interface CardUnit : NSObject
#property (assign) NSString *name;
#property (assign) NSString *gold;
#end
The Xcode compiler will take care of the rest.
See also this reply on SO
In the superclass MyClass:
#interface MyClass : NSObject
#property (nonatomic, strong, readonly) NSString *pString;
#end
#implementation MyClass
#synthesize pString = _pString;
#end
In the subclass MySubclass
#interface MySubclass : MyClass
#end
#implementation MySubclass
- (id)init {
if (self = [super init]) {
_pString = #"Some string";
}
return self;
}
The problem is that the compiler doesn't think that _pString is a member of MySubclass, but I have no problem accessing it in MyClass.
What am I missing?
The instance variable _pString produced by #synthesize is private to MyClass. You need to make it protected in order for MySubclass to be able to access it.
Add an ivar declaration for _pString in the #protected section of MyClass, like this:
#interface MyClass : NSObject {
#protected
NSString *_pString;
}
#property (nonatomic, strong, readonly) NSString *pString;
#end
Now synthesize the accessors as usual, and your variable will become accessible to your subclass.
I am familiar with this problem. You synthesize the variable in your .m class, so it is not imported along with the header since the _pString variable will be created as part of the implementation, and not the interface. The solution is to declare _pString in your header interface and then synthesize it anyway (it will use the existing variable instead of creating a private one).
#interface MyClass : NSObject
{
NSString *_pString; //Don't worry, it will not be public
}
#property (nonatomic, strong, readonly) NSString *pString;
#end
The given answer works perfectly fine. This is an alternative answer, that apparently Apple likes a bit more.
You can define a private extension of your class, a MyClass+Protected.h file, which needs to be included in MyClass.m and MySubclass.m.
Then, in this new file, you redefine the property as readwrite.
#interface MyClass ()
#property (strong, readwrite) NSString * pString;
#end
This alternative allows you to use the accessor self.pString rather than the ivar _pString.
Note: you still need to keep the definition of pString in your MyClass.h as is.
I want to use my class as a property in my project. The idea is that i have a class which contains all list ellements. The basic idea i show below in graph:
So i have a myContainerClass object, and i want to do in some other class:
#property (strong,nonatomic) MyContainerClass *obj;
and here i have error! I figure out that i can only use Foundations type as a #property. But Why? What is replacement for doing that (passing an object)?
No, you can use any class you like as a property
#property (nonatomic, strong) MyContainerClass* obj;
is perfectly legal provided that the compiler knows that MyContainerClass is a class. To do that in the header file, the best way is to use an #class forward declaration:
#class MyContainerClass;
#interface SomeOtherClass : NSObject
// method an property declarations
#property (nonatomic, strong) MyContainerClass* obj;
#end
And then include the header file in the implementation:
#import "MyContainerClass.h"
#implementation SomeOtherClass
#synthesize obj;
// other stuff
#end
What is the error you are getting? May be you are not importing MyContainerClass to where you want to use it.
#import "MyContainerClass.h"
Declare a category for an object that you want to add your property to:
#interface NSObject (MyContainerClassAdditions)
#property (nonatomic, strong) MyContainerClass *myContainerClass
#end
Then implement the setter and getter methods using objective c associated object trick:
#import <objc/runtime.h>
#implementation NSObject (MyContainerClassAdditions)
- (void)setMyContainerClass:(MyContainerClass *)myContainerClass {
objc_setAssociatedObject(self, "myContainerClass", myContainerClass, OBJC_ASSOCIATION_ASSIGN);
}
- (MyContainerClass *)myContainerClass {
return objc_getAssociatedObject(self, "myContainerClass");
}
#end