Cocoa-touch – Storing custom objects in an NSMutableArray in NSUserDefaults


I've recently been trying to store the search results of my iPhone app in the NSUserDefaults collection. I also use this to save user registration info successfully, but for some reason trying to store my NSMutableArray of custom Location classes always comes back empty.

I tried converting the NSMutableArray to a NSData element as of this post but I get the same result (Possible to save an integer array using NSUserDefaults on iPhone?)

The code samples I have tried are:


[prefs setObject:results forKey:@"lastResults"];
[prefs synchronize];


NSData *data = [NSData dataWithBytes:&results length:sizeof(results)];
[prefs setObject:data forKey:@"lastResults"];


NSData *data = [NSKeyedArchiver archivedDataWithRootObject:results];
[prefs setObject:data forKey:@"lastResults"];


lastResults = (NSMutableArray *)[prefs objectForKey:@"lastResults"];


NSData *data = [prefs objectForKey:@"lastResults"];
memcpy(&lastResults, data.bytes, data.length);  


NSData *data = [prefs objectForKey:@"lastResults"];
lastResults = [NSKeyedUnarchiver unarchiveObjectWithData:data];

After following advice below I have also implemented NSCoder in my object (ignore the overuse of NSString its temporary):

#import "Location.h"

@implementation Location

@synthesize locationId;
@synthesize companyName;
@synthesize addressLine1;
@synthesize addressLine2;
@synthesize city;
@synthesize postcode;
@synthesize telephoneNumber;
@synthesize description;
@synthesize rating;
@synthesize priceGuide;
@synthesize latitude;
@synthesize longitude;
@synthesize userLatitude;
@synthesize userLongitude;
@synthesize searchType;
@synthesize searchId;
@synthesize distance;
@synthesize applicationProviderId;
@synthesize contentProviderId;

- (id) initWithCoder: (NSCoder *)coder
    if (self = [super init])
        self.locationId = [coder decodeObjectForKey:@"locationId"];
        self.companyName = [coder decodeObjectForKey:@"companyName"];
        self.addressLine1 = [coder decodeObjectForKey:@"addressLine1"];
        self.addressLine2 = [coder decodeObjectForKey:@"addressLine2"]; = [coder decodeObjectForKey:@"city"];
        self.postcode = [coder decodeObjectForKey:@"postcode"];
        self.telephoneNumber = [coder decodeObjectForKey:@"telephoneNumber"];
        self.description = [coder decodeObjectForKey:@"description"];
        self.rating = [coder decodeObjectForKey:@"rating"];
        self.priceGuide = [coder decodeObjectForKey:@"priceGuide"];
        self.latitude = [coder decodeObjectForKey:@"latitude"];
        self.longitude = [coder decodeObjectForKey:@"longitude"];
        self.userLatitude = [coder decodeObjectForKey:@"userLatitude"];
        self.userLongitude = [coder decodeObjectForKey:@"userLongitude"];
        self.searchType = [coder decodeObjectForKey:@"searchType"];
        self.searchId = [coder decodeObjectForKey:@"searchId"];
        self.distance = [coder decodeObjectForKey:@"distance"];
        self.applicationProviderId = [coder decodeObjectForKey:@"applicationProviderId"];
        self.contentProviderId = [coder decodeObjectForKey:@"contentProviderId"];

- (void) encodeWithCoder: (NSCoder *)coder
    [coder encodeObject:locationId forKey:@"locationId"];
    [coder encodeObject:companyName forKey:@"companyName"];
    [coder encodeObject:addressLine1 forKey:@"addressLine1"];
    [coder encodeObject:addressLine2 forKey:@"addressLine2"];
    [coder encodeObject:city forKey:@"city"];
    [coder encodeObject:postcode forKey:@"postcode"];
    [coder encodeObject:telephoneNumber forKey:@"telephoneNumber"];
    [coder encodeObject:description forKey:@"description"];
    [coder encodeObject:rating forKey:@"rating"];
    [coder encodeObject:priceGuide forKey:@"priceGuide"];
    [coder encodeObject:latitude forKey:@"latitude"];
    [coder encodeObject:longitude forKey:@"longitude"];
    [coder encodeObject:userLatitude forKey:@"userLatitude"];
    [coder encodeObject:userLongitude forKey:@"userLongitude"];
    [coder encodeObject:searchType forKey:@"searchType"];
    [coder encodeObject:searchId forKey:@"searchId"];
    [coder encodeObject:distance forKey:@"distance"];
    [coder encodeObject:applicationProviderId forKey:@"applicationProviderId"];
    [coder encodeObject:contentProviderId forKey:@"contentProviderId"];


Best Solution

For loading custom objects in an array, this is what I've used to grab the array:

NSUserDefaults *currentDefaults = [NSUserDefaults standardUserDefaults];
NSData *dataRepresentingSavedArray = [currentDefaults objectForKey:@"savedArray"];
if (dataRepresentingSavedArray != nil)
    NSArray *oldSavedArray = [NSKeyedUnarchiver unarchiveObjectWithData:dataRepresentingSavedArray];
    if (oldSavedArray != nil)
        objectArray = [[NSMutableArray alloc] initWithArray:oldSavedArray];
        objectArray = [[NSMutableArray alloc] init];

You should check that the data returned from the user defaults is not nil, because I believe unarchiving from nil causes a crash.

Archiving is simple, using the following code:

[[NSUserDefaults standardUserDefaults] setObject:[NSKeyedArchiver archivedDataWithRootObject:objectArray] forKey:@"savedArray"];

As f3lix pointed out, you need to make your custom object comply to the NSCoding protocol. Adding methods like the following should do the trick:

- (void)encodeWithCoder:(NSCoder *)coder;
    [coder encodeObject:label forKey:@"label"];
    [coder encodeInteger:numberID forKey:@"numberID"];

- (id)initWithCoder:(NSCoder *)coder;
    self = [super init];
    if (self != nil)
        label = [[coder decodeObjectForKey:@"label"] retain];
        numberID = [[coder decodeIntegerForKey:@"numberID"] retain];
    return self;