NSOperation 简单使用

NSOperation 是一种多线程技术 ，起基本原理是把相应地操作放在队列里边 ，然后有队列分发处理。

队列的创建

/**
*  初始化一个队列
*
*  @return 初始化好的对列
*/
- (NSOperationQueue *)myQueue {
if (_myQueue == nil)
{
_myQueue = [[NSOperationQueue alloc] init];
}
return _myQueue;

}

向队列中添加操作

#pragma mark - 同时并发线程数量
/**
*  在队列中添加操作
*/
- (void)opDemo1
{

// 线程开启的数量是由GCD底层来决定的，程序员不能参与
// Mac 10.10 ＋ Xcode 6.0.1 GCD & NSOperation => 能建立 60～70 个线程
/**
设置最大并发数的好处，线程开启有消耗
3G     :   2~3条线程就可以了，线程少，流量少，省钱，省电
WIFI   :   5～6条线程就可以了，线程多，效率高，流量大，不花钱，可以随时充电！
*/
// NSOperation提供过了一个属性->最大并发线程数量
self.myQueue.maxConcurrentOperationCount = 3;
for (int i = 0; i < 100; i++)
{
[self.myQueue addOperationWithBlock:^{
// 阻塞自己的操作
[NSThread sleepForTimeInterval:0.5];
NSLog(@"%@ %d", [NSThread currentThread], i);
}];
}
}

队列可以暂停和继续

- (IBAction)pause {

// 先判断队列中是否有操作

if (self.myQueue.operationCount == 0) {

NSLog(@"无操作");

return;

}
// 挂起－》暂停，暂停的是队列，让队列暂时不再派发任务
NSLog(@"暂停");
[self.myQueue setSuspended:YES];
}

- (IBAction)resumue
{
// 先判断队列中是否有操作
if (self.myQueue.operationCount == 0)
{
NSLog(@"无操作");
return;
}
NSLog(@"继续");
[self.myQueue setSuspended:NO];

}

队列里边的操作默认是异步的

但是可以添加依赖关系 ，从而实现顺序执行的需求

/**
*  NSInvocationOperation 测试样例
*/
- (void)opDemo4
{
NSInvocationOperation *invocationOperation1 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(demo4Test1) object:nil];
NSInvocationOperation *invocationOperation2 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(demo4Test2) object:nil];
NSInvocationOperation *invocationOperation3 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(demo4Test3) object:nil];
NSInvocationOperation *invocationOperation4 = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(demo4Test4) object:nil];
/**
*  添加依赖关系
*/
[invocationOperation2 addDependency:invocationOperation1];
[invocationOperation3 addDependency:invocationOperation2];
[invocationOperation4 addDependency:invocationOperation3];
[self.myQueue addOperations:@[invocationOperation1, invocationOperation2, invocationOperation3,invocationOperation4] waitUntilFinished:NO];

}
- (void)demo4Test1
{
NSLog(@"test1  %@",[NSThread currentThread]);
}
- (void)demo4Test2
{
NSLog(@"test2  %@",[NSThread currentThread]);
}
- (void)demo4Test3
{
NSLog(@"test3  %@",[NSThread currentThread]);
}
- (void)demo4Test4
{
NSLog(@"test4  %@",[NSThread currentThread]);
}
#pragma mark - 操作的依赖->操作的执行顺序
/**
*  NSBlockOperation 测试阳历
*/
- (void)opDemo3
{

/**
测试的操作
例如：
1. 下载小电影压缩包
2. 解压缩
3. 保存文件
4. 通知用户
*/
NSBlockOperation *op1 = [NSBlockOperation blockOperationWithBlock:^{

NSLog(@"下载 %@", [NSThread currentThread]);

}];
NSBlockOperation *op2 = [NSBlockOperation blockOperationWithBlock:^{

NSLog(@"解压缩 %@", [NSThread currentThread]);

}];

NSBlockOperation *op3 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"保存 %@", [NSThread currentThread]);
}];
NSBlockOperation *op4 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"通知用户 %@", [NSThread currentThread]);

}];
// Dependency依赖
[op2 addDependency:op1];
[op3 addDependency:op2];
[op4 addDependency:op3];
// 一定注意不要出现循环依赖，
//    [op1 addDependency:op4];
// waitUntilFinished等待所有操作完成再继续
//    [self performSelectorOnMainThread:<#(SEL)#> withObject:<#(id)#> waitUntilDone:<#(BOOL)#>]

[self.myQueue addOperations:@[op1, op2, op3] waitUntilFinished:NO];

[[NSOperationQueue mainQueue] addOperation:op4];
}