How to add object in singleton NSMutableArray - ios

Question

I used to store the array data downloaded from the server.
But I can not save them in the singleton array.
It seems without access to the object.
Why ulatitude, ulongitude, uaccuracy, uplacename is nil?...
in .h file
#import <Foundation/Foundation.h>
#interface LocationData : NSObject
{
NSMutableArray *ulatitude;
NSMutableArray *ulongitude;
NSMutableArray *uaccuracy;
NSMutableArray *uplacename;
}
#property (nonatomic, retain) NSMutableArray *ulatitude;
#property (nonatomic, retain) NSMutableArray *ulongitude;
#property (nonatomic, retain) NSMutableArray *uaccuracy;
#property (nonatomic, retain) NSMutableArray *uplacename;
+ (LocationData*) sharedStateInstance;
#end
in .m file
#import "LocationData.h"
#implementation LocationData
#synthesize uaccuracy;
#synthesize ulatitude;
#synthesize ulongitude;
+ (LocationData*) sharedStateInstance {
static LocationData *sharedStateInstance;
#synchronized(self) {
if(!sharedStateInstance) {
sharedStateInstance = [[LocationData alloc] init];
}
}
return sharedStateInstance;
}
#end
use
[manager POST:urlStr parameters:params success:^(AFHTTPRequestOperation *operation, id responseObject)
{
NSLog(#"%#",responseObject);
// json response array
if ([responseObject isKindOfClass:[NSArray class]]) {
NSArray *responseArray = responseObject;
NSDictionary *responseDict = [[NSDictionary alloc] init];
LocationData* sharedState = [LocationData sharedStateInstance];
for(NSUInteger i=0; i < responseArray.count; i++)
{
responseDict = [responseArray objectAtIndex:i];
double dlat = [[responseDict objectForKey:#"lat"] doubleValue];
double dlng = [[responseDict objectForKey:#"lng"] doubleValue];
[[sharedState ulatitude] addObject:[NSString stringWithFormat:#"%f",dlat]];
[[sharedState ulongitude] addObject:[NSString stringWithFormat:#"%f",dlng]];
[[sharedState uaccuracy] addObject:[responseDict objectForKey:#"rad"]];
[[sharedState uplacename] addObject:[responseDict objectForKey:#"place_name"]];
}

Answer 1

You always need to initialize your arrays. You should do somewhere before you try to add something to them:
arrayName = [[NSMutableArray alloc] init];
otherwise you'll always get error because they have not been initialized.
In your case you should override your LocationData init function like this:
- (instancetype)init {
self = [super init];
if (self) {
self.yourArrayName = [[NSMutableArray alloc] init];
// And so on....
}
return self;
}

Answer 2

You need to initialize your object properly. Basically your member variables ("ivars") are pointing to nothing ("nil").
This initializer added to your .m file code do the job.
-(instancetype)init {
if ((self = [super init])) {
self.accuracy = [NSMutableArray array];
self.latitude = [NSMutableArray array];
self.longitude = [NSMutableArray array];
self.uplacename = [NSMutableArray array];
}
return self;
}
As a singleton pattern, I'd prefer the following:
+ (LocationData*) sharedStateInstance {
static LocationData *sharedStateInstance = nil;
static dispatch_once_t onceToken = 0;
dispatch_once(&onceToken, ^{
sharedStateInstance = [[LocationData alloc] init];
});
return sharedStateInstance;
}
Although singletons might not be as bad they are often said to be, I don't thing that this is a good usage for them. Your specific problem has nothing to do with that design choice, though.

Answer 3

Try this code. Write getters for your NSMutableArrays.
#import <Foundation/Foundation.h>
#interface LocationData : NSObject
#property (nonatomic, retain) NSMutableArray *ulatitude;
#property (nonatomic, retain) NSMutableArray *ulongitude;
#property (nonatomic, retain) NSMutableArray *uaccuracy;
#property (nonatomic, retain) NSMutableArray *uplacename;
+ (LocationData*) sharedStateInstance;
#end
#import "LocationData.h"
#implementation LocationData
#synthesize uaccuracy = _uaccuracy;
#synthesize ulatitude = _ulatitude;
#synthesize ulongitude = _ulongitude;
+ (LocationData*) sharedStateInstance {
static LocationData *sharedStateInstance;
#synchronized(self) {
if(!sharedStateInstance) {
sharedStateInstance = [[LocationData alloc] init];
}
}
return sharedStateInstance;
}
-(NSMutableArray*)uaccuracy
{
if(_uaccuracy == nil)
{
_uaccuracy = [[NSMutableArray alloc]init];
}
return uaccuracy;
}
-(NSMutableArray*)ulongitude
{
if(_ulongitude == nil)
{
_ulongitude = [[NSMutableArray alloc]init];
}
return ulongitude;
}
-(NSMutableArray*)ulatitude
{
if(_ulatitude == nil)
{
_ulatitude = [[NSMutableArray alloc]init];
}
return ulatitude;
}
-(NSMutableArray*)uplacename
{
if(_uplacename == nil)
{
_uplacename = [[NSMutableArray alloc]init];
}
return uplacename;
}
#end

Answer 4

you don't allocate/init any array...
you can create them in your singleton creation method
+ (LocationData*) sharedStateInstance {
static LocationData *sharedStateInstance;
#synchronized(self) {
if(!sharedStateInstance) {
sharedStateInstance = [[LocationData alloc] init];
sharedStateInstance.ulatitude = [[NSMutableArray alloc] init];
// (add others...)
}
}
return sharedStateInstance;
}

Answer 5

Replace your LocationData.m file with below code , this will work . As you have to alloc and init the array then only you can add object in array
+ (LocationData*) sharedStateInstance {
static LocationData *sharedStateInstance;
#synchronized(self) {
if(!sharedStateInstance) {
sharedStateInstance = [[LocationData alloc] init];
uaccuracy = [[NSMutableArray alloc]init];
ulatitude = [[NSMutableArray alloc]init];
ulongitude = [[NSMutableArray alloc]init];
uplacename = [[NSMutableArray alloc]init];
}
}
return sharedStateInstance;
}