Example Analysis of Multithreading in iOS

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1. Three multithreading technologies of iOS

1 、 NSThread

-advantages: NSThread is lighter and easier to use than the other two

-disadvantages: need to manage thread lifecycle, thread synchronization, locking, sleep, wake up, etc. The locking of data by thread synchronization will have some system overhead.

2 、 NSOperation

You don't need to worry about thread management and data synchronization, you can focus on the operations you need to perform.

3 、 GCD

Based on C language

Basic use basic use of NSThread

Method 1:

/ / block let thread = Thread.init {print ("1,-this is thread\ (Thread.current)")} thread.start ()

Method 2:

/ / SEL let thread2 = Thread.init (target: self, selector: # selector (text), object: nil) thread2.start () @ objc func text () {print ("2,-- this is thread\ (Thread.current)")}

Method 3:\

Self.performSelector (inBackground: # selector (text2), with: nil)

Output

Tips: you can add latency to any thread.

Print (thread.isCancelled) / / whether to cancel print (thread.isExecuting) / / whether to execute print (thread.isFinished) / / whether to complete print (thread.isMainThread) / / whether it is the basic use of the main thread NSOperation

Method 1:

Let queue = OperationQueue.init () / / maximum number of threads queue.maxConcurrentOperationCount = 2 queue.addOperation {sleep (1) print ("1111")} queue.addOperation {print ("2222")}

The output is as follows:

Method 2: priority can be set

Let queue = OperationQueue.init () let op = BlockOperation.init {print ("op")} op.queuePriority = .normal / / set priority queue.addOperation (op) let op2 = BlockOperation.init {print ("op2")} op2.queuePriority = .normal queue.addOperation (op2) queue .addOperation {print ("op3")}

Make a slight modification

Let queue = OperationQueue.init () let op = BlockOperation.init {sleep (1) print ("op")} op.queuePriority = .normal / / set priority queue.addOperation (op) let op2 = BlockOperation.init {sleep (1) print ("op2")} op2.queuePriority =. VeryHigh queue.addOperation (op2) queue.addOperation {print ("op3")}

The output is as follows:

The priorities are as follows:

Basic use of GCD

Method 1: queue.async async

Let queue = DispatchQueue.init (label: "com.zjb.concurrent", attributes: .concurrent) for i in 0.15 {queue.async {sleep (1) print ("this is\ (Thread.current)\ (I)")}}

Method 2: queue.sync synchronization

Let queue = DispatchQueue.init (label: "com.zjb.concurrent", attributes: .concurrent) for i in 0.15 {queue.sync {sleep (1) print ("this is\ (Thread.current)\ (I)")}}

Attach a piece of code on the network

For i in 1.. 10 {DispatchQueue.global (qos: DispatchQoS.QoSClass.default). Async {NSLog ("DispatchQoS.QoSClass.default,% d", I)} DispatchQueue.global (qos: DispatchQoS.QoSClass.background). Async {NSLog ("DispatchQoS.QoSClass.background,% d") I)} DispatchQueue.global (qos: DispatchQoS.QoSClass.unspecified). Async {NSLog ("DispatchQoS.QoSClass.unspecified,% d", I)} DispatchQueue.global (qos: DispatchQoS.QoSClass.userInitiated). Async {NSLog ("DispatchQoS.QoSClass.userInitiated,% d") I)} DispatchQueue.global (qos: DispatchQoS.QoSClass.userInteractive). Async {NSLog ("DispatchQoS.QoSClass.userInteractive,% d", I)} DispatchQueue.global (qos: DispatchQoS.QoSClass.utility). Async {NSLog ("DispatchQoS.QoSClass.utility,% d") I)}}

The highest priority userInteractive and the lowest background

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