First of all, I tried almost all the solutions given in stackoverflow but I didn't succeed in implement global vars, I even did a step by step tutorial and still I get the same errors.
heres the issue:
I have a program with severals views, I'd like to use variables on all of the views, so I used global variables,
I have:
GlobalVars.h
#import <UIKit/UIKit.h>
extern NSArray *truckBoxes;
extern NSArray *farmerlist;
extern NSString *farmerCardNumber;
extern NSString *fName;
@interface GlobalVars : NSObject
{
}
@end
GlobalVars.m
#import "GlobalVars.h"
NSArray *farmerlist;
NSArray *truckBoxes;
NSString *farmerCardNumber;
NSString *fName;
@implementation GlobalVars
{
}
@end
I include the file in the class (that is connected to the view controller):
under the .h file I add #import "GlobalVars.h
I can access farmerlist and truckBoxes from all over the app, but cant access fName or farmerCardNumber.
I can write to farmerCardNumber and read from the same view, but if I try to access it later on from another view I get
2013-10-26 11:11:45.612 C3Cms[10427:70b] Branch : 11558
2013-10-26 11:11:59.459 C3Cms[10427:70b] -[__NSArrayM length]: unrecognized selector sent to instance 0x8b7fbc0
2013-10-26 11:11:59.463 C3Cms[10427:70b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayM length]: unrecognized selector sent to instance 0x8b7fbc0'
*** First throw call stack:
(
0 CoreFoundation 0x02a3b5e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x014d58b6 objc_exception_throw + 44
2 CoreFoundation 0x02ad8903 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
3 CoreFoundation 0x02a2b90b ___forwarding___ + 1019
4 CoreFoundation 0x02a2b4ee _CF_forwarding_prep_0 + 14
5 Foundation 0x00f0db2d -[NSConcreteMutableAttributedString replaceCharactersInRange:withString:] + 39
6 Foundation 0x00f0e79a -[NSConcreteMutableAttributedString initWithString:attributes:] + 293
7 UIKit 0x001e8116 -[UILabel _setText:] + 97
8 UIKit 0x001e82d4 -[UILabel setText:] + 40
9 C3Cms 0x00001c1d -[printForm viewDidLoad] + 77
10 UIKit 0x0014e9a8 -[UIViewController loadViewIfRequired] + 696
11 UIKit 0x0014ec44 -[UIViewController view] + 35
12 UIKit 0x00168a72 -[UINavigationController _startCustomTransition:] + 778
13 UIKit 0x00175757 -[UINavigationController _startDeferredTransitionIfNeeded:] + 688
14 UIKit 0x00176349 -[UINavigationController __viewWillLayoutSubviews] + 57
15 UIKit 0x002af39d -[UILayoutContainerView layoutSubviews] + 213
16 UIKit 0x000a5dd7 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 355
17 libobjc.A.dylib 0x014e781f -[NSObject performSelector:withObject:] + 70
18 QuartzCore 0x030d772a -[CALayer layoutSublayers] + 148
19 QuartzCore 0x030cb514 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 380
20 QuartzCore 0x030cb380 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 26
21 QuartzCore 0x03033156 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 294
22 QuartzCore 0x030344e1 _ZN2CA11Transaction6commitEv + 393
23 QuartzCore 0x03034bb4 _ZN2CA11Transaction17observer_callbackEP19__CFRunLoopObservermPv + 92
24 CoreFoundation 0x02a0353e __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 30
25 CoreFoundation 0x02a0348f __CFRunLoopDoObservers + 399
26 CoreFoundation 0x029e13b4 __CFRunLoopRun + 1076
27 CoreFoundation 0x029e0b33 CFRunLoopRunSpecific + 467
28 CoreFoundation 0x029e094b CFRunLoopRunInMode + 123
29 GraphicsServices 0x029979d7 GSEventRunModal + 192
30 GraphicsServices 0x029977fe GSEventRun + 104
31 UIKit 0x0003b94b UIApplicationMain + 1225
32 C3Cms 0x00002882 main + 130
33 libdyld.dylib 0x019bc70d start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
One way to implement global variables, and to manage their lifetime (i.e. that they are initialized) and even to provide global methods is to implement a class exposing those variables/methods and to use the singleton pattern:
GlobalVars.h:
#import <Foundation/Foundation.h>
@interface GlobalVars : NSObject
{
NSMutableArray *_truckBoxes;
NSMutableArray *_farmerlist;
NSString *_farmerCardNumber;
NSString *_fName;
}
+ (GlobalVars *)sharedInstance;
@property(strong, nonatomic, readwrite) NSMutableArray *truckBoxes;
@property(strong, nonatomic, readwrite) NSMutableArray *farmerList;
@property(strong, nonatomic, readwrite) NSString *farmerCardNumber;
@property(strong, nonatomic, readwrite) NSString *fName;
@end
GlobalVars.m:
#import "GlobalVars.h"
@implementation GlobalVars
@synthesize truckBoxes = _truckBoxes;
@synthesize farmerList = _farmerList;
@synthesize frameCardNumber = _frameCardNumber;
@synthesize fName = _fName;
+ (GlobalVars *)sharedInstance {
static dispatch_once_t onceToken;
static GlobalVars *instance = nil;
dispatch_once(&onceToken, ^{
instance = [[GlobalVars alloc] init];
});
return instance;
}
- (id)init {
self = [super init];
if (self) {
_truckBoxes = [[NSMutableArray alloc] init];
_farmerlist = [[NSMutableArray alloc] init];
// Note these aren't allocated as [[NSString alloc] init] doesn't provide a useful object
_farmerCardNumber = nil;
_fName = nil;
}
return self;
}
@end
You can then use these global variables like this, for example:
GlobalVars *globals = [GlobalVars sharedInstance];
globals.fName = @"HelloWorld.txt";
[globals.farmerList addObject:@"Old Macdonald"];
[self processList:[globals farmerList]];
However, please consider: