How to create a key per initiated object using NSUserdefaults - objective-c

Question

I have a custom NSObject and I instantiate this object using a manager.
My NSObjets are passed into a mutable array so that I can access their properties(name) via uipickerview once save method is initialised.
When I close my app, all my objects disappear as expected.
I would like to save my objects in the NSUserDefaults so I have implemented the NSUserdefaults in my manager. This is to save my objects so that they are loaded when the application is launched in the uipickerviewcontroller.
However my application crashes when I load the uipickerviewcontroller.
Here is the log after the crash:
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[PacsServer encodeWithCoder:]: unrecognized selector sent to instance 0x7fd0a2e7fa20'
PacsServer.h
#import <Foundation/Foundation.h>
#interface PacsServer : NSObject
#property ( nonatomic) NSString *pacsName;
#property (nonatomic) NSString*username;
#property ( nonatomic) NSString*password;
#property (nonatomic) NSString *wadoUrl;
#property ( nonatomic) NSString *apiDirectory;
#property ( nonatomic) NSString *dataArrayIncludesUsernamePasswordWadoLoginWebServiceAndSecurity;
#end
pacsserver.m
#import "PacsServer.h"
#implementation PacsServer
#end
manager.h
#import <Foundation/Foundation.h>
#interface PacsServerManager : NSObject
+(instancetype)pacsManager ;
#property NSMutableArray *pacsServers;
#end
Manager.m
#import "PacsServerManager.h"
#import "PacsServer.h"
#implementation PacsServerManager
+(instancetype)pacsManager {
static id instance;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
instance = [[self alloc] init];
});
return instance;
}
-(id) init {
if(self =[super init]){
PacsServer *server= [[PacsServer alloc] init];
_pacsServers = [NSMutableArray arrayWithObjects:server, nil];
NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];
NSData *serverData = [NSKeyedArchiver archivedDataWithRootObject:_pacsServers];
[standardUserDefaults setObject:serverData forKey:#"server"];
[standardUserDefaults setObject:_normalArray forKey:#"Servers" ];
[standardUserDefaults synchronize];
}
return self;
}
#end
Here in the save method below I get the username, password and other fields from the text fields. To be able to save all these into keychain.
-I first save these in an array then pass this array to NSData using datawithJsonObject.
Then save this array as NSString into keychain
Add nsobjects via manager
#import "AddPACSViewController.h"
#import "PacsServerManager.h"
#import "PacsServer.h"
#import <KeychainItemWrapper.h>
#interface AddPACSViewController ()
#end- (void)saveForAddPacs:(id)sender {
.
.
.
.
NSString *pacsDataArray = [keychain objectForKey:(__bridge id)kSecValueData];
PacsServer *newPacsServer = [[PacsServer alloc] init];
newPacsServer.pacsName= pacsNameFromAddPacsView;
newPacsServer.dataArrayIncludesUsernamePasswordWadoLoginWebServiceAndSecurity = pacsDataArray;
[[PacsServerManager pacsManager].pacsServers addObject:newPacsServer];
[self performSegueWithIdentifier:#"Save" sender:self];
}
Access the objects in uipickerview
pickerviewcontroller.m
- (NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component{
NSLog(#"Pacs data in settingsview:%#", [PacsServerManager pacsManager].pacsServers);
PacsServer *server = [[PacsServerManager pacsManager].pacsServers objectAtIndex:row];
NSString *name = server.pacsName;
NSLog(#"Servername:%#, and the data %#", server.pacsName, server.dataArrayIncludesUsernamePasswordWadoLoginWebServiceAndSecurity);
NSLog(#"%#", [[NSUserDefaults standardUserDefaults] dictionaryRepresentation]);
return name;
}
Any help would be appreciated.
Thank you.

Answer 1

You need to address a couple of things here.
1) The exception is caused because of this line:
NSData *serverData = [NSKeyedArchiver archivedDataWithRootObject:_pacsServers];
When you archive any object, that object needs to implement the <NSCoding> protocol. When you archive aggregate objects (like NSArray and NSSet) each of the objects that are contained in the array or set need to implement the <NSCoding> protocol also. In this case PacsServer is being sent an encodeWithCoder: message which it doesn't implement.
See this tutorial on NSCoding.
2) Is it really a good idea to be persisting these objects in the NSUserDefaults? NSUserDefaults is really designed for small bits of information like whether you should show a help item, or is this the first time the user has launched your app. Perhaps you'd be better off saving this data in a separate .dat file or even using a different method like CoreData or sqlite (if you have a large amount of data).