首先,我尝试了堆栈溢出中给出的几乎所有解决方案,但我没有成功实现全局变量,我什至做了一个分步教程,但仍然得到同样的错误。
问题来了:
我有一个带有多个视图的程序,我想在所有视图上使用变量,所以我使用了全局变量,
我有:
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
我将文件包含在类中(连接到视图控制器):在 .h 文件下我添加了#import "GlobalVars.h
我可以从整个应用程序访问farmerlist
和truckBoxes
,但无法访问fName
或farmerCardNumber
。
我可以写入farmerCardNumber
并从同一视图读取,但是如果我稍后尝试从另一个视图访问它,我会得到
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
实现全局变量、管理它们的生存期(即它们被初始化)甚至提供全局方法的一种方法是实现一个公开这些变量/方法的类并使用单例模式:
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
然后,您可以像这样使用这些全局变量,例如:
GlobalVars *globals = [GlobalVars sharedInstance];
globals.fName = @"HelloWorld.txt";
[globals.farmerList addObject:@"Old Macdonald"];
[self processList:[globals farmerList]];
但是,请考虑:
- 你不需要像这样使用全局变量;你应该能够创建一个模型对象,该对象是根据需要创建的,并将对它的引用传递给视图。 这是MVC。
- 您还发布了一个不相关问题的堆栈跟踪,这在Objective-C中非常常见;一旦您意识到此错误是什么,只有您可以修复此错误。
该错误与全局变量无关。错误消息
-[__NSArrayM length]: unrecognized selector sent to instance 0x8b7fbc0
表示您在代码中的某处分配了NSMutableArray
以farmerCardNumber
而不是NSString
.
例如,如果您执行类似
farmerCardNumber = [someDictionary objectForKey:@"someKey"];
[someDictionary objectForKey:@"someKey"]
恰好是一个数组而不是一个字符串,然后farmerCardNumber
指向该数组,即使它被声明为指针一个字符串。
我正在我所有的项目中使用并且工作正常。
全球资源.h
#import <Foundation/Foundation.h>
@class GlobalResource;
extern GlobalResource * R;
@interface GlobalResource : NSObject
{
NSString *myVar;
}
+ (void) loadGlobalResources;
@property (strong, nonatomic, readwrite) NSString *myVar;
@end
全球资源
#import "GlobalResource.h"
GlobalResource *R;
@implementation GlobalResource
@synthesize myVar;
- (void) loadGlobalResources
{
R = [[GlobalResource alloc] init];
}
- (id)init
{
self = [super init];
if (self) {
myVar = @"My Value";
}
return self;
}
@end
如何使用
#import "GlobalResource.h"
//then access value as bellow
[GlobalResource loadGlobalResource];
NSLog(@"%@",R.myVar); //value will print here
你为什么不尝试这样的事情:
#import "GlobalVars.h"
NSArray *farmerlist;
NSArray *truckBoxes;
NSString *farmerCardNumber = nil;
NSString *fName = nil;
@implementation GlobalVars
{
}
@end
或
#import "GlobalVars.h"
NSArray *farmerlist;
NSArray *truckBoxes;
NSString *farmerCardNumber = @"";
NSString *fName = @"";
@implementation GlobalVars
{
}
@end
而且似乎您已将可变数组传递给字符串变量,这就是您收到该错误的原因。
删除该行
#import "GlobalVars.h"
来自GlobalVars.m.
你不能把 extern 变量放到 *.h 文件中。
所以在 GlobalVariables.m 中,你有:
extern NSArray *farmerlist;
NSArray *farmerlist;
和:
@interface GlobalVars : NSObject
{
}
@end
@implementation GlobalVars
{
}
@end
不需要
[编辑]
例如:
其他.m
#import "GlobalVars1.h"
GlobalVars1.h
extern NSArray *truckBoxes;
extern NSArray *farmerlist;
extern NSString *farmerCardNumber;
extern NSString *fName;
GlobalVars.h
#import <UIKit/UIKit.h>
@interface GlobalVars : NSObject
{
}
@end
GlobalVars.m
#import "GlobalVars.h"
NSArray *farmerlist;
NSArray *truckBoxes;
NSString *farmerCardNumber;
NSString *fName;
@implementation GlobalVars
{
}
@end