在Objective-C中使用全局变量

First of all, I tried almost all the solutions given in * but I didn't succeed in implement global vars, I even did a step by step tutorial and still I get the same errors.

首先，我尝试了几乎所有在*中给出的解决方案，但我没有成功实现全局变量，我甚至做了一步一步的教程，但我仍然得到相同的错误。

heres the issue:

继承人的问题：

I have a program with severals views, I'd like to use variables on all of the views, so I used global variables,

我有一个包含多个视图的程序，我想在所有视图上使用变量，所以我使用了全局变量，

I have:

我有：

GlobalVars.h

GlobalVars.h

#import <UIKit/UIKit.h>
extern NSArray *truckBoxes;
extern NSArray *farmerlist;
extern NSString *farmerCardNumber;

extern NSString *fName;

@interface GlobalVars : NSObject
{
}

@end

GlobalVars.m

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

我将该文件包含在类中（连接到视图控制器）：在.h文件下我添加#import“GlobalVars.h

I can access farmerlist and truckBoxes from all over the app, but cant access fName or farmerCardNumber.

我可以从应用程序的各个位置访问farmerlist和truckBoxes，但无法访问fName或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

我可以写到farmerCardNumber并从同一视图中读取，但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

6 个解决方案

#1

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:

实现全局变量并管理它们的生命周期（即它们被初始化）甚至提供全局方法的一种方法是实现暴露这些变量/方法并使用单例模式的类：

GlobalVars.h:

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:

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:

然后，您可以使用这样的全局变量，例如：

GlobalVars *globals = [GlobalVars sharedInstance];
globals.fName = @"HelloWorld.txt";
[globals.farmerList addObject:@"Old Macdonald"];
[self processList:[globals farmerList]];

However, please consider:

但请考虑：

• You don't need to use global variables like this; you should be able to create a model object which is created as necessary and reference to it passed to the views. This is MVC.
• 你不需要像这样使用全局变量;您应该能够创建一个模型对象，该对象是根据需要创建的，并引用它传递给视图。这是MVC。
• You also posted a stack trace of an unrelated issue which is extremely common with Objective-C; only you can fix this error, once you realize what it is.
• 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;一旦你意识到它是什么，只有你能解决这个错误。

#2

The error has nothing to do with global variables. The error message

该错误与全局变量无关。错误消息

-[__NSArrayM length]: unrecognized selector sent to instance 0x8b7fbc0

indicates that you somewhere in your code assigned a NSMutableArray to farmerCardNumber instead of a NSString.

表示您在代码中的某个位置将NSMutableArray分配给farmerCardNumber而不是NSString。

For example, if you do something like

例如，如果你做了类似的事情

farmerCardNumber = [someDictionary objectForKey:@"someKey"];

and [someDictionary objectForKey:@"someKey"] happens to be an array and not a string, then farmerCardNumber points to that array, even if it was declared as pointer to a string.

并且[someDictionary objectForKey：@“someKey”]恰好是一个数组而不是一个字符串，那么farmerCardNumber指向该数组，即使它被声明为指向字符串的指针。

#3

Why donot you try something like:

为什么不尝试类似的东西：

#import "GlobalVars.h"

NSArray *farmerlist;
NSArray *truckBoxes;
NSString *farmerCardNumber = nil;
NSString *fName = nil;
@implementation GlobalVars
{

}
@end

or

要么

#import "GlobalVars.h"

NSArray *farmerlist;
NSArray *truckBoxes;
NSString *farmerCardNumber = @"";
NSString *fName = @"";
@implementation GlobalVars
{

}
@end

AND it seems like you have passed mutable array to your string varibale, that is why you are getting that error.

似乎你已经将可变数组传递给你的字符串varibale，这就是你得到那个错误的原因。

#4

I am using in all my project and working fine.

我在我的所有项目中使用并且工作正常。

GlobalResource.h

GlobalResource.h

#import <Foundation/Foundation.h>

@class GlobalResource;

extern GlobalResource * R;

@interface GlobalResource : NSObject
{
    NSString *myVar;
}
+ (void) loadGlobalResources;

@property (strong, nonatomic, readwrite) NSString *myVar;

@end

GlobalResource.m

GlobalResource.m

#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

How to use

如何使用

#import "GlobalResource.h"

//then access value as bellow

[GlobalResource loadGlobalResource];
NSLog(@"%@",R.myVar); //value will print here

#5

Remove the line

删除该行

#import "GlobalVars.h"

from GlobalVars.m.

来自GlobalVars.m。

#6

You can't put extern variables to *.h file.

您不能将外部变量放入* .h文件。

So in GlobalVariables.m you have:

所以在GlobalVariables.m中你有：

extern NSArray *farmerlist;
NSArray *farmerlist;

And:

和：

@interface GlobalVars : NSObject
{
}

@end

@implementation GlobalVars
{

}
@end

are not needed

不需要

[edit]

[编辑]

for example:

例如：

Other.m

Other.m

#import "GlobalVars1.h"

GlobalVars1.h

GlobalVars1.h

extern NSArray *truckBoxes;
extern NSArray *farmerlist;
extern NSString *farmerCardNumber;

extern NSString *fName;

GlobalVars.h

GlobalVars.h

#import <UIKit/UIKit.h>

@interface GlobalVars : NSObject
{
}

@end

GlobalVars.m

GlobalVars.m

#import "GlobalVars.h"

NSArray *farmerlist;
NSArray *truckBoxes;
NSString *farmerCardNumber;
NSString *fName;
@implementation GlobalVars
{

}
@end