I am at my wits end with a property declaration in a iOS class. In my .h file I have the following declaration :
#property (strong, nonatomic)NSString *sessionID;
In my .m file I have this code :
- (void)setSessionID:(NSString *)aSessionID
{
_sessionID = aSessionID;
// Custom code to set this in a global context
}
This is all fine and compiles with no issues. Now I need to have the sessionID return a default value if nothing is set, however the moment I add this line :
- (NSString *)sessionID
{
return _sessionID ? _sessionID : #"defaultSession";
}
then the first line in the setSessionID:
_sessionID = aSessionID;
causes an error with "Use of undeclared function _sessionID. Did you mean aSessionID", I am at my wits end to figure out what is causing it.. I have so many classes with variables and have never seen this before... what is causing this? I restarted Xcode, cleaned out the project and no luck.. If I remove the - (NSString *)sessionID method, then it stops complaining.. but the moment I add the method declaration the Xcode marks it as an error.
Anypointers accepted! :)
Edit: I also noticed, that in this class if I add any property accessor method it complains about the ivar.. e.g. I have another property declared
#property (strong, nonatomic) NSString *userEmail
The moment I add -(NSString *)userEmail, the ivar _userEmail usage above it all becomes undeclared.. :(
If you override both the setter and getter of a property, the compiler will not automatically synthesize the backing ivar for you. You need to do a manual synthesis,
#synthesize sessionID = _sessionID;
Related
I was able to see an interesting case using
Estimote nearables SDK
They have a class ESTNearable with property called zone.
// ENUM
typedef NS_ENUM(NSInteger, ESTNearableZone ) {
ESTNearableZoneUnknown = 0,
ESTNearableZoneImmediate,
ESTNearableZoneNear,
ESTNearableZoneFar,
};
// CLASS
#interface ESTNearable : NSObject <NSCopying, NSCoding>
// ...
#property (nonatomic, assign, readonly) ESTNearableZone zone;
// ...
#end
So when I try to use this method in Swift, compiler fails with that error:
As I understand there is some kind of compiler bug and for some reason it believes that I want to use old zone method from NSObject - (struct _NSZone *)zone OBJC_ARC_UNAVAILABLE; I can use other specific properties of that class without any problems.
As I use an SDK I can not change the name of the zone method. I believe I can write some kind of obj-c category, add some new method there, which will return value of original one, but I do not want to add obj-c classes in my project.
Is there any possibility to call this method from swift as I believe correct zone method will be called for class instances?
Thanks in advance!
Here I found the same question. I answered more deeply there. I could not find something more good, so I went ahead with my old assumptions.
I Added this category to Bridging Header. It worked fine.
#import <EstimoteSDK/EstimoteSDK.h>
#interface ESTNearable (Ex)
/// Solving the compiler problem that "zone" method is unavailable in Swift
#property (readonly) ESTNearableZone nearableZone;
#end
// Implementation
#implementation ESTNearable (Ex)
- (ESTNearableZone)nearableZone
{
return self.zone;
}
#end
After that I just used nearableZone method in Swift
var zone = someNearable.nearableZone
Having an Objective c base class:
#interface ObjcClass : NSObject {
NSString *aVariable_;
}
And a swift sub-class:
class SwiftClass : ObjcClass {
func init() {
// aVariable_ can't be accessed here. An Objective-c derived
// class has direct access to it's super's instance variables!
}
}
How do I access ObjcClass aVariable_ from within SwiftClass?
Great query. We have tried to hard to get this done. The only working solution I found
get value by using self.valueForKey("aVariable_")
set value using self.setValue("New Value", forKey: "aVariable_")
Hope that helps. Possible solution without altering super class.
I couldn't find a "proper" way to do this, but I needed badly for it to work. My solution was to create a simple getter method in my Objective C superclass, like this:
header file
#interface ObjcClass : NSObject {
NSString *myVariable;
}
- (NSString *)myVariable;
in the implementation file
- (NSString *)myVariable {
return myVariable;
}
I'd love to hear of a better way of doing it, but this at least works.
I've searched a lot for this.
Eventually I changed my code from:
#interface PrjRec : NSObject {
#public
NSString* name;
}
#end
To:
#interface PrjRec : NSObject {
}
#property NSString* name;
#end
similar to #JasonTyler solution.
Then I can access to my object property from Swift code with simple dot notation <object instance>.name,
But I needed to change all existing objective-c references from
<object instance>->name
To:
<object instance>.name
or
_name
if inside class unit.
I hope for a better solution too.
This worked as a pretty neat solution for me, just adding a Swift variable like:
var myInstanceVar: String {
return self.value(forKey: "myInstanceVar") as! String
}
If you are willing to have a property, then you can create the property to fit your needs.
#interface ObjcClass : NSObject {
NSString *aVariable_;
}
#property (nonatomic) NSString *aVariable_;
...
#implementation ObjcClass
#synthesize aVariable_ = aVariable_;
This allows the variable to be accessed as inst->aVariable_ or as inst.aVariable_. In the Objective C class the variable can be accessed as aVariable_ or self.aVariable_.
I seriously don't know why anyone does instance variables anymore (for one, they're private by default) vs properties. See Giorgio Calzolato's answer on this (apart from his last line about looking for a better solution - that IS the best solution :) ).
In my case I already had a property and was extra perplexed over why it didn't work. But I realized that the property had a custom time and it needed to be added into my SDK-Bridging-Header.h file.
So if your property is set to a custom type like this:
#property (nonatomic, weak) IBOutlet SDKMyCustomObject *customObject;
...then remember to add it to the bridging header.
I am making a simple app and this piece of code has been giving me issues.
Here is my property.
In ConverisonCalculator.h
#property (strong, nonatomic)NSString *startingUnit;
In Viewcontroller.m I am using this code and everytime I NSLog it I am getting (null)
_calculator.startingUnit = #"FPS";
Also here is my lazy instantiation of the object.
- (ConversionCalculator *)calculator{
if (!_calculator) _calculator = [[ConversionCalculator alloc]init];
return _calculator; }
I hope this is enough for you to answer my question. I am not override the default setter either.
Here is my logging.
NSLog(#"%#", [_calculator startingUnit]);
_calculator.startingUnit = #"FPS";
This is not using your property. This is direct access to the instance variable, so your lazy loading code is never called.
If you define properties, always access them through the property:
self.calculator.startingUnit = #"FPS";
Otherwise, you might as well be using instance variables. The only exception is inside the accessor methods themselves, or in init or dealloc methods (in some cases).
the strangest thing happened. Although I don't think I touched anything in that class, suddenly it started telling me it couldn't find an array in a class...
Here are the errors:
basically it cannot access the mutable array in baseobject (custom Car.h type)
(semantic issue: property objectReadyForCoreDatabase not found in object of type CarPacket (false, because it is declared))
if([baseObject.objectsReadyForCoreDataBaseInput count]<kLenght )
{
}
car packet .h
#import <Foundation/Foundation.h>
#import "ResponsePacket.h"
#interface CarPacket : ResponsePacket
#property (nonatomic, copy) NSString *objectID;
#property (nonatomic, retain) NSMutableArray *objectsReadyForCoreDataBaseInput;
#property (nonatomic, assign) NSInteger timeStamp;
#end
It is weird because on the same page where I get the error if I type object.objectID it recognizes that but not object.objectReadyForCoreDataBaseInput (also it just suddenly stopped working)
Please let me know if you have any ideas... Thank you
I tried restoring to previous snapshots and it had no effect... it still showed the error (even though I know on that date it didn't)
You haven't shared much about the context of where you're making the call (and seeing the error). That said, my guess would be one of two things: The calling class isn't familiar with the receiving class (CarPacket), or, the calling class doesn't know that baseObject is a CarPacket.
Where are you calling from? Make sure the calling class imports the headers. Since I don't know where you're calling from, let's say it's from within UnknownClass:
UnknownClass.m
#import UnknownClass.h
#import CarPacket.h // This should make your class familiar
#implementation UnknownClass
The other thing is that you need to make sure that at the time you're touching the baseObject, your UnknownClass instance knows that it is dealing with a CarPacket instance, e.g.:
- (void)someMethodOfUnknownClass
{
CarPacket *baseObject = (CarPacket *)baseObject; // Cast baseObject if it hasn't been declared as a CarPack in scope...
if([baseObject.objectsReadyForCoreDataBaseInput count]<kLenght )
{
}
}
please i got errors when i try to read the content of a variable in view2 which was initialized in view1, i explain :
view1 is named RechercherViewController
view2 is named StationsSurLaCarteViewController
RechercherViewController.h :
#property (nonatomic,copy) NSString *typeCarburantChoisi;
RechercherViewController.m :
#synthesize typeCarburantChoisi;
StationsSurLaCarteViewController.h
#import "RechercherViewController.h"
#interface StationsSurLaCarteViewController : UIViewController {
IBOutlet AideStationsSurLaCarteViewController *aideStationsSurLaCarteViewController;
IBOutlet UITextField *textField;
}
#end
StationsSurLaCarteViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
textField.text=RechercherViewController.typeCarburantChoisi;
}
when building the app, i got actually two errors :
error: expected specifier-qualifier-list before 'StationsSurLaCarteViewController'
and
error: accessing unknown 'typeCarburantChoisi' class method
thx for help :)
First of all you have defined an instance property typeCarburantChoisi but in your StationsSurLaCarteViewController.m code you are trying to access kind of a class property (btw, there is no such thing in Objective-C). You will instead need a reference to your RechercherViewController instance and ask it for the property – this will resolve the second compiler error.
Regarding the first error I am not really sure what happened here. Maybe you have an error in your RechercherViewController.h file?
In any case, you should rather not import the interface file into StationsSurLaCarteViewController.h. Instead, use
#class RechercherViewController;
and import the full declaration in your implementation file StationsSurLaCarteViewController.m only.
Also, did you mix up AideStationsSurLaCarteViewController and RechercherViewController in your example?