Operation / OperationQueue

// Create

// default OperationQueue() is a concurrent OperationQueue
let op1 = OperationQueue()
op1.name = "op1"
//op1.maxConcurrentOperationCount = 5
op1.qualityOfService = .default

// 1.setting underlyingQueue based on DispatchQueue
// The value of this property should only be set if there are no operations in the queue; 
// setting the value of this property when operationCount is not equal to 0 raises an invalidArgumentException. 
// The value of this property must not be the value returned by dispatch_get_main_queue(). 
// The quality-of-service level set for the underlying dispatch queue overrides any value set 
// for the operation queue's qualityOfService property.
let serialQueue = DispatchQueue(label: "serialQueue")
let concurrentQueue = DispatchQueue(label: "concurrentQueue", attributes: .concurrent)

op1.underlyingQueue = serialQueue
//op1.underlyingQueue = concurrentQueue

// 2. 最大并发数
op1.maxConcurrentOperationCount = 1

// 3. Suspended
op1.isSuspended = false
// 任务开始后没发暂停，比如for 5000 次，一半的时候暂停，for也会执行全部5000次
/*
When the value of this property is false, 
the queue actively starts operations that are in the queue and ready to execute. 

Setting this property to true prevents the queue from starting any queued operations, 
but already executing operations continue to execute. 

You may continue to add operations to a queue that is suspended 
but those operations are not scheduled for execution until you change this property to false.
*/


// 4. cancel all operations
op1.cancelAllOperations()
/*
Cancels all queued and executing operations.
This method calls the cancel() method on all operations currently in the queue.
Canceling the operations does not automatically remove them from the queue or stop those 
that are currently executing.
*/


// 5. 等待全部任务完成再回到当前线程

//阻塞当前线程直到此队列中的所有任务执行完毕
//[queue waitUntilAllOperationsAreFinished]; NSLog(@"all done");
//op1.waitUntilAllOperationsAreFinished()

// 6. addOperation
print("init in \(Thread.current)")

typealias BlockType = () -> Void
var block1: BlockType = {
    print("block 1 in \(Thread.current)")
}
var block2: BlockType = {
    print("operation2 in \(Thread.current)")
}

op1.addOperation(block1)
op1.addOperation {
    print("block 1 - 1 in \(Thread.current)")
}

let operation2 = BlockOperation(block: block2)
op1.addOperation(operation2)

// 7. add Operation dependency
let finishBlockOp = BlockOperation {
    print("finish operation2 \(Thread.current)")
}
finishBlockOp.addDependency(operation2)
op1.addOperation(finishBlockOp)


// 8. add completion block
// The exact execution context for your completion block 
// is not guaranteed but is typically a secondary thread.

let operation3 = BlockOperation { 
    () -> Void in
    print("operation 3 in \(Thread.current)")
}
operation3.completionBlock = {
    () -> Void in
    print("completion block of operation 3 in \(Thread.current)")
}

op1.addOperation(operation3)

// 9. subclass of operation
class DwOperation: Operation {
    // MARK: - Properties
    var downloadedImage: UIImage?
    var urlStr: NSString?

    // MARK: - func for running
    override func main() -> Void {
        // if cancelled itself
        if (self.isCancelled) {
            return
        }

        guard let validUrlStr = urlStr,
            let validUrl = URL(string: validUrlStr as String)
            else {
                return
        }
        // if cancelled itself
        if (self.isCancelled) {
            return
        }
        // tring to download the data and transfer to UIImage
        // TODO: Something
        print("I'm DwOperation with url: \(validUrl) in \(Thread.current)")
    }
}
let task = DwOperation()
task.urlStr = "11"
weak var weakTask = task  // break retain cycle
task.completionBlock = {
    print("finish task with url \(weakTask?.urlStr) in \(Thread.current)")

}
op1.addOperation(task)

NSOperation / NSOperationQueue

Qperation

• can run with start()
• default is sync
• within PerationQueue, default is async

How to use

• create OperationQueue
  • setting maxConcurrentCount
  • Setting DispatchQueue
• create Operation or inherit Operation
  • override main()
  • implement completion block (watch out retain cycle)
• push Operation into OperationQueue, automatically start()

API

NSOperation

• NSOperation && NSOperationQueue

操作OPeration

NSoperation 可以调用start执行， 默认是同步的

如果将NSOperation添加到NSOperationQueue中，会自动异步执行

//创建操作 with selector
NSOperation*op1 = [[NSInvocationOperationalloc]initWithTarget:selfselector:@selector(download1) object:nil];

//创建操作 with block
NSBlockOperation*op2 = [NSBlockOperationblockOperationWithBlock:^{
    NSLog(@"block operation : %@", [NSThreadcurrentThread]);
}];

//创建自定义操作
BLOperation *BLOp = [[BLOperation alloc]init];

queue只有两种：

1. [NSOperationQueue mainQueue],
2. [NSOperationQueue alloc] init] //其他队列，包涵串行和并行，自动放到子线程
3. • 串行
   • 并行：默认

用法

1.创建队列

2.创建任务

3.添加任务到队列即可自动start

或者省略step2

直接[queue addOperationWithBlock:^{ xxx }];

自定义operation，重写main()添加任务。 只有operation的子类才能执行

其他Queue操作

1. 最大并发数

queue.maxCurrentOperationCount = 1

2. Suspended

queue.suspended = NO

任务开始后没发暂停，比如for 5000 次，一半的时候暂停，for也会执行全部5000次

3. Cancel

同上， 任务开始没发取消。所以认为干预

if (!isCacnelled) return;

4. dependency

op1, op2, op3

op3 op1, op2之后执行

［op3 addDependency:op1]; [op3 addDependency:op2];

千万不能循环依赖，可以夸队列依赖

5. completionBlock

监听单个任务执行完

op5.completionBlock{ xxx; };

6. 等待全部任务完成再回到当前线程

//阻塞当前线程直到此队列中的所有任务执行完毕
[queue waitUntilAllOperationsAreFinished]; NSLog(@"all done");

7. 线程通信

- (void) operationDownload {
    NSOperationQueue*queue = [[NSOperationQueuealloc]init];
    [queue addOperationWithBlock:^{
        NSURL*url = [NSURLURLWithString:@"[http://www.tophdwallpaersland.com/wp-content/uploads/2016/03/Excellent-Wide_1080p-1920x1080-HD-Wallpaper-1024x576.jpg"](http://www.tophdwallpaersland.com/wp-content/uploads/2016/03/Excellent-Wide_1080p-1920x1080-HD-Wallpaper-1024x576.jpg")\];
        NSData*data = [NSDatadataWithContentsOfURL:url];
        UIImage*image = [UIImageimageWithData:data];

        //回到主队列
        [[NSOperationQueuemainQueue]addOperationWithBlock:^{
            [self.imageView setImage:image];
        }];
    }];
}

依赖

- (void)testDependency {
    NSOperationQueue*queue = [[NSOperationQueuealloc] init];
    NSBlockOperation*op1 = [NSBlockOperationblockOperationWithBlock:^{
        NSLog(@"download1----%@", [NSThreadcurrentThread]);
    }];

    NSBlockOperation*op2 = [NSBlockOperationblockOperationWithBlock:^{
        NSLog(@"download2----%@", [NSThreadcurrentThread]);
    }];

    NSBlockOperation*op3 = [NSBlockOperationblockOperationWithBlock:^{
        NSLog(@"download3----%@", [NSThreadcurrentThread]);
    }];

    NSBlockOperation*op4 = [NSBlockOperationblockOperationWithBlock:^{
        for(NSIntegeri =0; i<10; i++) {
            NSLog(@"download4----%@", [NSThreadcurrentThread]);
        }
    }];

    NSBlockOperation*op5 = [NSBlockOperationblockOperationWithBlock:^{
        NSLog(@"download5----%@", [NSThreadcurrentThread]);
    }];

    op5.completionBlock = ^{
        NSLog(@"op5执行完毕---%@", [NSThreadcurrentThread]);
    };

    // 设置依赖    
    [op3 addDependency:op1];
    [op3 addDependency:op2];
    [op3 addDependency:op4];
    [queue addOperation:op1];
    [queue addOperation:op2];
    [queue addOperation:op3];
    [queue addOperation:op4];
    [queue addOperation:op5];
}

// res 
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