IBOutlet control is nil - cocoa

Question

I am trying to set text of a NSTextField from a different class..
This is what i have:
Preferences.h
#interface Preferences : NSObject
{
IBOutlet NSTextField *selectionPointX;
}
#property (nonatomic, unsafe_unretained) IBOutlet NSTextField *dateTimeFormatPreview;
- (void)getSelection:(NSPoint)point :(NSSize)size;
#end
Preferences.m (only what's needed)
#import "Preferences.h"
#implementation Preferences
NSUserDefaults *userDefaults = nil;
int cPx;
int cPy;
int cSw;
int cSh;
- (void)getSelection:(NSPoint)point :(NSSize)size{
cPx = (int) point.x;
cPy = (int) point.y;
cSw = (int) size.width;
cSh = (int) size.height;
[self saveSelection];
}
- (void)saveSelection{
NSPoint p;
p.x = cPx;
p.y = cPy;
NSSize s;
s.width = cSw;
s.height = cSh;
[userDefaults setObject:NSStringFromPoint(p) forKey:#"selectionPoint"];
NSLog(#"Saved Window Position: X: %i Y: %i", cPx, cPy);
[userDefaults setObject:NSStringFromSize(s) forKey:#"selectionSize"];
NSLog(#"Saved Window Size: W: %i H: %i", cSw, cSh);
[userDefaults synchronize];
[selectionPointX setIntegerValue:cPx]; // selectionPointX is nil
}
#end
I call getSelection from a different class, passing values to it.
In the Interface Builder, i have a NSObject with class Preferences, and from it i have connected the Outlet to the controller.
But when debugging selectionPointX is nil and so not updating my TextField.
I'm new to objective-c so probably i'm doing it wrong.
I have searched a lot but can't find a solution.
Any help appreciated, thank you.
EDIT: I think i have found the problem. Since i call the method from a different class, i create another instance of that class, and so all connections are not hooked up.
I did that:
Preferences *prefs = [[Preferences alloc] init];
[prefs getSelection:(NSPoint)wPos :(NSSize)wSize];
How i can call the same method, but using the current instance of Preferences that is loaded by the XIB?

Answer 1

I have a LocalSettingsController which is similiar to what you want here. In order to use the same Preferences instance all the time implement the Singleton pattern. Here's the code:
#implementation LocalSettingsController
+ (id)alloc
{
return self.sharedSettings;
}
+ (id)allocWithZone: (NSZone *)zone
{
return self.sharedSettings;
}
+ (instancetype)sharedSettings
{
static LocalSettingsController* singleton = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
singleton = [[self localAlloc] localInit];
});
return singleton;
}
- (id)init
{
return self;
}
+ (id)localAlloc
{
return [super allocWithZone: NULL];
}
- (id)localInit
{
return [super init];
}
In code you can use the sharedSettings member, in IB you'd place an NSObject in your xib and change its instance type to LocalSettingsController (or in your case Preferences).