how to start a global thread in swift - ios

Question

Is there any way to start and stop a thread in swift along with it making the thread global also so that it can used anywhere.
As shown below, this is how i create thread in swift
var objThrd = SimpleClass()
let thread = NSThread(target: objThrd , selector: "createSimpleObj", object: nil)
Please give an example if feasible. Or can we achieve this via NSOperation ?

Answer 1

Use Grand Central Dispatch
let myQueue: dispatch_queue_t = dispatch_queue_create("com.example.queue", nil)
dispatch_async(myQueue, { () -> Void in
// Execute some code
})

Answer 2

I use a small function, which uses Central Dispatch, to start a new thread:
typealias FuncPointer = () -> () // Pointer to a function
func startprocess (_ f: FuncPointer)
{
let atrb = DispatchQueue.GlobalAttributes.qosUserInteractive
DispatchQueue.global(attributes: atrb).async(group: DispatchGroup())
{
f()
}
}
To start a function as a thread, you call it like:
startprocess(myFuncName)
The function "myFuncName" is a function without parameters and without a result. This example works in Swift 3.0 beta 3 and Xcode 8 beta 3. You can start multiple threads after each other without waiting for something.
You can use the following function:
_ = group.wait(timeout: DispatchTime.distantFuture)
To wait, until all threads of a specific group have finished. So you start the threads not with DispatchGroup(), but with a predefined group variable. This is an easy way to handle a group of more than 1 threads. Example for six threads:
let group = DispatchGroup()
let myThreadCount: Int = 6
for _ in 1...myThreadCount
{
DispatchQueue.global(attributes: DispatchQueue.GlobalAttributes.qosUserInteractive).async(group: group)
{
Calculate(NumberOfSteps / ThreadCurrentCount)
}
}
_ = group.wait(timeout: DispatchTime.distantFuture)