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:
Save:
[prefs setObject:results forKey:@"lastResults"];
[prefs synchronize];
or
NSData *data = [NSData dataWithBytes:&results length:sizeof(results)];
[prefs setObject:data forKey:@"lastResults"];
or
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:results];
[prefs setObject:data forKey:@"lastResults"];
Load:
lastResults = (NSMutableArray *)[prefs objectForKey:@"lastResults"];
or
NSData *data = [prefs objectForKey:@"lastResults"];
memcpy(&lastResults, data.bytes, data.length);
or
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"];
self.city = [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"];
}
Solution 1:
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];
else
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;
}
Solution 2:
I think you've gotten an error in your initWithCoder method, at least in the provided code you don't return the 'self' object.
- (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"];
self.city = [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"];
}
return self; // this is missing in the example above
}
I use
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:results];
[prefs setObject:data forKey:@"lastResults"];
and
NSUserDefaults *currentDefaults = [NSUserDefaults standardUserDefaults];
NSData *dataRepresentingSavedArray = [currentDefaults objectForKey:@"lastResults"];
if (dataRepresentingSavedArray != nil)
{
NSArray *oldSavedArray = [NSKeyedUnarchiver unarchiveObjectWithData:dataRepresentingSavedArray];
if (oldSavedArray != nil)
objectArray = [[NSMutableArray alloc] initWithArray:oldSavedArray];
else
objectArray = [[NSMutableArray alloc] init];
}
and it works perfect for me.
With regards,
Stefan