How to use Static Variable to save a string in objective-c?

Question

I want to use Static Var to save a NSString. So I define a Static Var in a .h file like this:

#ifndef GlobalParameters_h
#define GlobalParameters_h

//access token
static NSString *applicationToken;

#endif

In class A, I change the static var like this:

#import "ClassA.h"
#import "GlobalParameters.h"

extern NSString *applicationToken;

@implementation ClassA

+ (void)parseResponse:(NSString *)response
{
    NSDictionary *responseDic = [response objectFromJSONString];

    NSString *token = [responseDic objectForKey:@"token"];

    applicationToken = [token copy];

    NSLog(@"%@",applicationToken);
}

When the debugger run to

applicationToken = [token copy];

I found the "applicationToken" is nil,but the next sentence

NSLog(@"%@",applicationToken);

can output the right value in console! And in ClassB , the "applicationToken" is nil too. I don't know why the static var is nil. I think the compiler will find the definition of "applicationToken" in GlobalParameters.h.But why I can't modify the static value?

Thanks for your help:)

Cy-4AH · Accepted Answer · 2014-10-08 09:33:18Z

2

static global variable mean that it's own for every object-file it's used. So there is willbe own applicationToken for ClassA, ClassB.

To create global variable for all object-files you need this:

In GlobalParameters.h:

#ifndef GlobalParameters_h
#define GlobalParameters_h

//access token
extern NSString *applicationToken;

#endif

In GlobalRarameters.m:

#import "GlobalParameters.h"

NSString *applicationToken;

P.S. I hope you use ARC, because if not, then applicationToken = [token copy]; will cause memory leaks.

answered Oct 8, 2014 at 9:33

Cy-4AH

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5 Comments

Tsich'i Over a year ago

Thanks for your help.But,I use the keyword "extern". I remember that "extern" could expand the scope of the var.

Cy-4AH Over a year ago

@Tsich'i, ok. use extern, just don't use static.

Tsich'i Over a year ago

In GlobalParameters_h , I modify "staic NSString *applicationToken" to "NSString *applicationToken" . Then in ClassA ,"applicationToken" can be modified correctly. Is there any posibilities the "applicationToken" be released during MyApp is running? @Cy-4AH

Tsich'i Over a year ago

I hope "applicationToken" can be used during MyApp is running.

Cy-4AH Over a year ago

@Tsich'i, I have already wrote in which file how should be defined yours variable, why you doesn't use it?

Injectios · Accepted Answer · 2014-10-08 09:58:15Z

0

Hey Its working fine , I am checking like this

Once check the are you getting "responseDic" (or) not , Check the The dictionary have token key

   static NSString *applicationToken;
   applicationToken = @"srinivas";
   NSLog(@"%@",applicationToken);

   NSDictionary *responseDic = [NSDictionary dictionaryWithObject:@"static" forKey:@"token"];

   NSString *token = [responseDic objectForKey:@"token"];

   applicationToken = [token copy];

   NSLog(@"%@",applicationToken);
       [AppDelegate parseResponse:responseDic];

edited Oct 8, 2014 at 9:58

Injectios

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answered Oct 8, 2014 at 9:44

srinivas n

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1 Comment

Tsich'i Over a year ago

Yes, I check the value. The "token" has the correct value. But when I set the value to the static "applicationToken" , it's failure.

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