I'm having trouble creating a nice way of passing a collection around to different view controllers. For example, I created a custom class called Message with a bunch of attributes. I want to have a global NSMutableArray of those stored in a global variable of sorts called messages that I can add to or get from anywhere. Everyone on Stackoverflow says not to use your delagate class to store global variables so I created a singleton class called Shared. In there I created a property for the NSMutableArray called messages like this:
@interface Shared : NSObject {
}
@property (nonatomic, retain) NSMutableArray *messages;
+(Shared *) sharedInstance;
@end
And my .h file is (the important part):
#import "Shared.h"
static Shared* sharedInstance;
@implementation Shared
@synthesize messages;
static Shared *sharedInstance = nil;
-(id) init {
self = [super init];
if (self != nil){
}
return self;
}
-(void) initializeSharedInstance {
}
+ (Shared *) sharedInstance{
@synchronized(self) {
if (sharedInstance == nil){
sharedInstance = [[self alloc] init];
[sharedInstance initializeSharedInstance];
}
return (sharedInstance);
}
}
In my other view controller, I first import "Shared.h", then try this:
[[Shared sharedInstance].messages addObject:m];
NSLog([NSString stringWithFormat:@"Shared messages = %@", [Shared sharedInstance].messages]);
It keeps printing null instead of the the collection of m objects. Any thoughts?
You need to have a static variable.
In .h:
@interface Shared : NSObject
{
NSMutableArray *messages;
}
@property (nonatomic, retain) NSMutableArray *messages;
+ (Shared*)sharedInstance;
@end
in .m:
static Shared* sharedInstance;
@implementation Shared
@synthesize messages;
+ (Shared*)sharedInstance
{
if ( !sharedInstance)
{
sharedInstance = [[Shared alloc] init];
}
return sharedInstance;
}
- (id)init
{
self = [super init];
if ( self )
{
messages = [[NSMutableArray alloc] init];
}
return self;
}