Static和Extern关键字理解

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.view.backgroundColor = [UIColor whiteColor];
    [self test];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    
    NSLog(@"---------- viewWillAppear -------------");
    [self test];
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    
    NSLog(@"---------- viewDidAppear -------------");
    [self test];
}

- (void)test {
    NSString *normalString;
    static NSString *staticString;
    
    NSLog(@"normal = %p, static = %p", &normalString, &staticString);
}

@end

static NSInteger age;