英文:
Timer does not get called inside Grand Central Dispatch async
问题
我有一个简单的定时器，每1秒将在异步的Grand Central Dispatch中执行一个日志打印：
import Foundation
do {
let GDC = DispatchQueue.init(label: "GDC", attributes: .concurrent)
GDC.async {
Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { timer in
print(3333)
}
}
} catch let err {
print(err)
}
然而，在Playground中运行时，我看不到print或err的日志？
英文:
I have a simple timer each 1 second will execute logging print inside an async Grand Central Dispatch:
import Foundation
do {
let GDC = DispatchQueue.init(label: "GDC", attributes: .concurrent)
GDC.async {
Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { timer in
print(3333)
}
}
} catch let err {
print(err)
}
However I don't see the log of print or err when running in Playground?
答案1
得分: -1
在技术上，要解决这个问题，你需要使用 RunLoop.current.run() 创建一个永久循环。
所以：
do {
let GDC = DispatchQueue.init(label: "GDC", attributes: .concurrent)
GDC.async {
Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { timer in
print(3333)
}
RunLoop.current.run()
}
}
应该可以工作。然而，在这种情况下，你真的需要定时器吗，这是一个更大的问题。考虑使用 DispatchQueue.asyncAfter 作为一个例子（根据用例可能还有更多选项）。
英文:
Technically to solve the issue you need to create a permanent loop using RunLoop.current.run()
So:
do {
let GDC = DispatchQueue.init(label: "GDC", attributes: .concurrent)
GDC.async {
Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { timer in
print(3333)
}
RunLoop.current.run()
}
}
should work. However do you really need timers in this case is a bigger question. Consider using DispatchQueue.asyncAfter for example (and possibly there are more options, depending on use case).
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