NSThread Basics
About
NSthread class is the most basic and lightweight multi-threading technology used for multithreading in iOS which can be used to directly manipulate thread objects.
References: Apple Doc
Create a Thread
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func testThread(){
let thread1 = Thread.init(target: self, selector: #selector(loopMethod), object: nil)
thread1.name = "Thread 1"
thread1.start()
}
@objc func loopMethod(){
for i in 0...100 {
print("Index \(i)")
}
}
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func testThreadUsingBlock() {
let thread2 = Thread.init {
for i in 0...100 {
print("Index \(i)")
}
}
thread2.name = "Thread 2"
thread2.start()
}
Start the thread internally calls the main method. The default main method automatically calls the selector. If you customize the Thread subclass, you can override this method and implement the tasks in it. Do not call the main method directly. Always start the thread by calling start method.
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class ASThread: Thread {
override func main() {
print(ASThread.current.name ?? "")
}
}
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func testSubclassedThread() {
let thread = ASThread.init()
thread.name = "Custom Thread"
thread.start()
}
Stop/block thread
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open class func sleep(until date: Date)
Block the current thread until the specified time. When the thread is blocked, no running loop processing occurs.
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open class func sleep(forTimeInterval ti: TimeInterval)
Block the current thread until the specified time interval. When the thread is blocked, no running loop processing occurs.
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open class func exit()
Terminate the current thread.
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open func cancel()
Stop performing the current task. Set the thread to the canceled state.
Thread priority
open var threadPriority: Double
The priority of the thread is specified by a floating-point number between 0.0 and 1.0, where 1.0 is the highest priority. The default is 0.5. A thread with a higher priority is more likely to be scheduled by the CPU.
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open class func setThreadPriority(_ p: Double) -> Bool
Set the priority of the current thread. If the priority setting is successful, return True, otherwise, return False.
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open var qualityOfService: QualityOfService
QualityOfService:
QualityOfService.userInteractive: The highest priority, mainly used to provide interactive UI operations, such as handling click events and drawing images to the screen
QualityOfService.userInitiated: The second highest priority, mainly used to execute tasks that need to return immediately
QualityOfService.default: The default priority, when the priority is not set, the thread default priority
QualityOfService.utility: Normal priority, mainly used for tasks that do not need to return immediately
QualityOfService.background: Background priority, used for tasks that are not urgent at all
Thread Environment Attributes
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open class func isMultiThreaded() -> Bool
Returns whether the application is multi-threaded.
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open class var current: Thread { get }
Get the currently executing thread object.
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open class var isMainThread: Bool { get }
A Boolean value to determine whether the current thread is the main thread. If it is the main thread, return True, otherwise return False.
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open class var main: Thread { get }
Get the main thread object.
Thread execution states
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open var isExecuting: Bool { get }
A Boolean value to determine whether the thread is executing. If the thread is executing, return True, otherwise, return False.
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open var isFinished: Bool { get }
A Boolean value that determines whether the thread has completed execution. If the thread has finished executing, return True, otherwise, return False.
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open var isCancelled: Bool { get }
A Boolean value that determines whether the thread is canceled. If the thread is canceled, return True, otherwise, return False. Calling cancel methods of the object can set the value of this property to true. If the thread supports cancellation, it should check this attribute periodically (in the main method), and exit if it returns true.