iOS-----线程同步与线程通信

LCAccount.h

@interface LCAccount : NSObject

// 封装账户编号、账户余额两个属性

@property （nonatomic， copy）NSString* accountNO；// 账户编号

@property （nonatomic， readonly）CGFloat balance；// 账户余额

- （id）initWithAccountNo：（NSString*）accountNo  balance：（CGFloat）balance；

- （void）draw：（CGFloat）drawAmount；

@end

该LCAccount类还需要提供一个draw：方法，该方法用于从该账号中取钱。

LCAccount.m

@implementation LCAccount

- (id)initWithAccountNo:(NSString *)aAccount balance:(CGFloat)aBalance

{

self = [super init];

if(self)

{

_accountNo = aAccount;

_balance = aBalance;

}

return self;

}

// 提供了一个draw方法来完成取钱操作

- (void)draw:(CGFloat)drawAmount

{

// 账户余额大于取钱数目

if(self.balance >= drawAmount)

{

// 吐出钞票

NSLog(@”%@取钱成功!吐出钱票:%g”, [NSThread currentThread].name , drawAmount);// ①

//  [NSThread sleepForTimeInterval:0.001 ];

// 修改余额

_balance = _balance – drawAmount;

NSLog(@”\t 余额为:%g”, self.balance);

}

else

{

NSLog(@”%@取钱失败!余额不足!”,  [NSThread currentThread].name);// ②

}

}

- (NSUInteger) hash

{

return [self.accountNo hash];

}

- (BOOL)isEqual:(id)anObject

{

if(self == anObject)

return YES;

if(anObject != nil

&& [anObject class] == [LCAccount class])

{

LCAccount* target = (LCAccount*)anObject;

return [target.accountNo isEqualToString:self.accountNo];

}

return NO;

}

@end

LCViewController.m

@implementation LCViewController

LCAccount* account;

- (void)viewDidLoad

{

[super viewDidLoad];

// 创建一个账号

account = [[LCAccount alloc] initWithAccountNo:@”321231” balance: 1000.0 ];

}

- (IBAction)draw:(id)sender

{

// 创建第1个线程对象

NSThread* thread1 = [[NSThread alloc] initWithTarget:self

selector:@selector(drawMethod:)

object:[NSNumber numberWithInt:800]];

// 创建第2个线程对象

NSThread* thread2 = [[NSThread alloc] initWithTarget:self

selector:@selector(drawMethod:)

object:[NSNumber numberWithInt:800]];

// 启动两条线程

[thread1 start];

[thread2 start];

}

- (void)drawMethod:(NSNumber *)drawAmount

{

// 直接调用accont对象的draw方法来执行取钱操作

[account draw:drawAmount.doubleValue];

}

@end

// 提供一个线程安全的draw方法来完成取钱操作

- (void) draw:(CGFloat)drawAmount

{

// 使用self作为同步监视器,任何线程进入下面的同步代码块之前

// 必须先获得self账户的锁定----其他线程无法获得锁,也就无法修改它

// 这种做法符合”加锁 →修改→释放锁”的逻辑

@synchronized(self)

{

// 账户余额大于取钱数目

if(self.balance >= drawAmount)

{

// 吐出钞票

NSLog(@”%@取钱成功! 吐出钞票:%g”, [NSThread currentThread].name , drawAmount);

[NSThread  sleepForTimeInterval:0.001];

// 修改余额

_balance = _balance – drawAmount;

NSLog(@”\tyue为: %g”, self.balance);

}

else

{

NSLog(@”%@取钱失败!余额不足!”, [NSThread currentThread].name);

}

}// 同步代码块结束,该线程释放同步锁

}

LCAccount.m

@implementation LCAccount

NSCondition* cond；

BOOL flag；

- （id）init

{

self = [super init];

if(self)

{

cond = [[NSCondition alloc] init];

}

return self;

}

-(id)initWithAccountNo:(NSString*)aAccount balance:(CGFloat)aBalance

{

self = [super init];

if(self)

{

cond = [[NSCondition alloc] init];

_accountNo = aAccount;

_balance = aBalance;

}

return self;

}

// 提供一个线程安全的draw方法来完成取钱操作

- (void)draw:(CGFloat)drawAmount

{

// 加锁

[cond lock];

// 如果flag为NO,则表明账户中还没有人存钱进去,取钱方法阻塞

if(!flag)

{

[cond wait];

}

else

{

// 执行取钱操作

NSLog(”%@ 取钱:%g”, [NSThread currentThread].name,    drawAmount);

_balance -= drawAmount;

NSLog(@”账户余额为:”%g”, self.balance);

// 将标识账户是否已有存款的旗标设为NO

flag = NO;

// 唤醒其他线程

[cond broadcast];

}

[cond unlock];

}

- (void)deposit:(CGFloat)depositAmount

{

[cond lock];

// 如果flag为YES,则表明账户中已有人存钱进去了,存钱方法阻塞

if(flag)// 1

{

[cond wait];

}

else

{

// 执行存款操作

NSLog(@”%@ 存款:%g”, [NSThread currentThread].name, depositAmount);

_balance += depositAmount;

NSLog(@”账户余额为:%g”, self.balance);

// 将标识账户是否已有存款的旗标设为YES

flag = YES;

// 唤醒其他线程

[cond broadcast];

}

[cond unlock];

}

// 此处省略了hash和isEqual:方法

…

@end

ViewController.m

@implementation ViewController

LCAccount* account;

- (void)viewDidLoad

{

[super viewDidLoad]；

// 创建一个账号

account = [[LCAccount alloc] initWithAccountNo：@”321321” balance:1000.0];

}

- (IBAction)depositDraw:(id)sender

{

// 创建 启动3个存钱者线程

[NSThread detachNewThreadSelector:@selector(drawMethod:) toTarget:self withObject:[NSNumber numberWithDouble:800.0]];

[NSThread detachNewThreadSelector:@selector(drawMethod:) toTarget:self withObject:[NSNumber numberWithDouble:800.0]];

[NSThread detachNewThreadSelector:@selector(drawMethod:) toTarget:self withObject:[NSNumber numberWithDouble:800.0]];

// 创建，启动取钱者线程

[NSThread detachNewThreadSelector:@selector(depositMethod:) toTarget:self withObject:[NSNumber numberWithDouble:800.0]];

}

- (void)drawMethod:(NSNumber*)drawAmount

{

[NSThread currentThread].name = @”甲”;

// 重复100次执行取钱操作

for(int i = 0;i < 100; i++)

{

[account draw:drawAmount.doubleValue];

}

}

- (void)depositMethod:(NSNumber*) depositAmount

{

[NSThread currentThread].name = @”乙”;

// 重复100次执行存款操作
for(int i = 0; i < 100; i++)
{
[account deposit:depositAmount.doubleValue];
}
}
@end