//非线程安全写法

static UserHelper * helper = nil;

+ (UserHelper *)sharedUserHelper {

if (helper == nil) {

helper = [[UserHelper alloc] init];

}

 return helper;

}

//线程安全写法1

static UserHelper * helper = nil;

+ (UserHelper *)sharedUserHelper {

 @synchronized(self) {

  

  if (helper == nil) {

   helper = [[UserHelper alloc] init];

  }

 }

 return helper;

}

+ (void)initialize {

 

 if ([self class] == [UserHelper class]) {

  helper = [[UserHelper alloc] init];

 }

}

//线程安全写法3（苹果推荐，主要用这个）

static UserHelper * helper = nil;

+ (UserHelper *)sharedUserHelper {

 

static dispatch_once_t onceToken;

 dispatch_once(&onceToken, ^{

  helper = [[UserHelper alloc] init];

 });

 

 return helper;

}

#import <Foundation/Foundation.h>

#import "UserHelper.h"

 

void func() {

 

 static dispatch_once_t onceToken;

 dispatch_once(&onceToken, ^{

 NSLog(@"haha");

 });

}

 

int main(int argc, const char * argv[]) {

 @autoreleasepool {

 

// [UserHelper logout];

 

 if ([UserHelper isLogin]) {

  

  UserHelper * helper = [UserHelper sharedUserHelper];

  NSLog(@"username = %@ password = %@",helper.userName,helper.password);

  

 } else {

  

  char name[20];

  char pwd[20];

  NSLog(@"请输入用户名");

  scanf("%s",name);

  NSLog(@"请输入密码");

  scanf("%s",pwd);

  

  NSString * userName = [[NSString alloc] initWithUTF8String:name];

  NSString * password = [[NSString alloc] initWithUTF8String:pwd];

  

  if (userName && password) {

  

  [UserHelper loginWithUserName:userName password:password];

  

  UserHelper * helper = [UserHelper sharedUserHelper];

  NSLog(@"username = %@ password = %@",helper.userName,helper.password);

  

  }

 }

 

// UserHelper * help1 = [UserHelper sharedUserHelper];

// help1.userName = @"dahuan";

// help1.password = @"123456";

// NSLog(@"%p",help1);

// NSLog(@"%@",help1.userName);

// NSLog(@"%@",help1.password);

//

// 

// UserHelper * help2 = [UserHelper sharedUserHelper];

// help2.password = @"zxc";

// NSLog(@"%p",help2);

// NSLog(@"%@",help1.userName);

// NSLog(@"%@",help1.password);

 

 }

 return 0;

}

 //class.h

#import <Foundation/Foundation.h>

 

@interface UserHelper : NSObject

 

//1、创建类方法，返回对象实例 shared default current

 

+ (UserHelper *)sharedUserHelper;

 

@property (nonatomic, copy) NSString * userName;

 

@property (nonatomic, copy) NSString * password;

 

+ (BOOL)isLogin;

 

+ (void)loginWithUserName:(NSString *)userName password:(NSString *)password;

 

+ (void)logout;

 

@end

 

// class.m

#import "UserHelper.h"

 

//2、创建一个全局变量

 

#define Path @"/Users/dahuan/Desktop/data"

 

static UserHelper * helper = nil;

 

@implementation UserHelper

 

//+ (void)initialize {

// 

// if ([self class] == [UserHelper class]) {

// helper = [[UserHelper alloc] init];

// }

//}

 

+ (UserHelper *)sharedUserHelper {

 

 //3、判断对象是否存在，若不存在，创建对象

 //线程安全

// @synchronized(self) {

// 

// if (helper == nil) {

//  helper = [[UserHelper alloc] init];

// }

// }

 

 //gcd 线程安全

 static dispatch_once_t onceToken;

 dispatch_once(&onceToken, ^{

 helper = [[UserHelper alloc] init];

 });

 

 return helper;

}

 

- (instancetype)init {

 

 if (self = [super init]) {

 

 NSString * data = [NSString stringWithContentsOfFile:Path encoding:NSUTF8StringEncoding error:nil];

 if (data) {

  NSArray * array = [data componentsSeparatedByString:@"-"];

  _userName = array[0];

  _password = array[1];

 }

 }

 return self;

}

 

+ (BOOL)isLogin {

 

 UserHelper * helper = [UserHelper sharedUserHelper];

 if (helper.userName && helper.password) {

 return YES;

 }

 return NO;

}

 

+ (void)loginWithUserName:(NSString *)userName password:(NSString *)password {

 

 UserHelper * helper = [UserHelper sharedUserHelper];

 helper.userName = userName;

 helper.password = password;

 

 NSArray * array = @[userName,password];

 NSString * data = [array componentsJoinedByString:@"-"];

 [data writeToFile:Path atomically:YES encoding:NSUTF8StringEncoding error:nil];

}

 

+ (void)logout {

 

 NSFileManager * fm = [NSFileManager defaultManager];

 

 if ([fm fileExistsAtPath:Path]) {

 [fm removeItemAtPath:Path error:nil];

 }

}

 

@end