单例 全局变量

// MyCommon.h:
@interface MyCommon
class MyCommon : NSObject
{
    int user;
};
@property(assign) int user;
+ (MyCommon *)singleton;
@end
// MyCommon.m:
@implementation MyCommon
static MyCommon * MyCommon_Singleton = nil;
+ (MyCommon *)singleton
{
    if (nil == MyCommon_Singleton)
    {
        MyCommon_Singleton = [[MyCommon_Singleton alloc] init];
    }
    return MyCommon_Singleton;
}
@end
The MyCommon singleton is then used anywhere in my application as follows:

int user = [MyCommon singleton].user;