Instance variable 'variable' accessed in class method error

Question

I have a variable declared in the header file :

@interface

int _nPerfectSlides;

and

@property (nonatomic, readwrite) int _nPerfectSlides;

and I have a method that I declared in the header :

+ (void) hit;

The method has the following code in it :

+ (void) hit {
    NSLog(@"hit");
    _nPerfectSlides = 0;
    [_game showHit];
}

now for some reason I get the error "Instance variable '_nPerfectSlides' accessed in class method" error and it seems like I cant access any variables inside the method. What am I doing wrong?

Answer 1

1. For + (void)hit:Only have access to the self object.

--Step 1: Remove follwing line from header file

@property (nonatomic, readwrite) int _nPerfectSlides;

--Step 2:

• Add int _nPerfectSlides in your class file globally..
• That means declare before @implementation

Eg: In .m File

#import "Controller.h"
int _nPerfectSlides // Add like this before @implementation

@implementation Controller

---

2. For - (void)hit:Only have access to the instance methods

Answer 2

If you meant to make this an instance method, change that + to -.

Answer 3

An instance variable is, as its name suggests, only accessible in the instance methods (those declared with -). Class methods (declared with +) have no access to instance variable, no more than they have access to the self object.

Answer 4

I know this is old, but it still comes up. Try making it a static. Here's I'm altering the code a bit to make it increment.

// Hit.h

#import <Foundation/Foundation.h>
@interface Hit : NSObject
+ (void)hit;
@end

// Hit.m

#import "Hit.h"
@implementation Hit
static int val = 0;
+ (void)hit {
    val += 1;
    [self showHit];
}
+ (void)showHit {
    NSLog(@"hit value: %d", val);
}
@end

//main.m

#import <Foundation/Foundation.h>
#import "Hit.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        [Hit hit];
        [Hit hit];
        [Hit hit];
    }
    return 0;
}