如何使用线程在迅速?
dispatchOnMainThread:^{
NSLog(@"Block Executed On %s", dispatch_queue_get_label(dispatch_get_current_queue()));
}];
如何使用线程在迅速?
dispatchOnMainThread:^{
NSLog(@"Block Executed On %s", dispatch_queue_get_label(dispatch_get_current_queue()));
}];
当前回答
你必须将你想要在后台运行的更改与你想要在UI上运行的更新分开:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
// do your task
dispatch_async(dispatch_get_main_queue()) {
// update some UI
}
}
其他回答
斯威夫特5
为了简化,创建一个“DispatchQueue+Extensions.swift”文件,内容如下:
import Foundation
typealias Dispatch = DispatchQueue
extension Dispatch {
static func background(_ task: @escaping () -> ()) {
Dispatch.global(qos: .background).async {
task()
}
}
static func main(_ task: @escaping () -> ()) {
Dispatch.main.async {
task()
}
}
}
用法:
Dispatch.background {
// do stuff
Dispatch.main {
// update UI
}
}
来自Jameson Quave的教程
斯威夫特2
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
//All stuff here
})
快4.倍
把这些放到文件中:
func background(work: @escaping () -> ()) {
DispatchQueue.global(qos: .userInitiated).async {
work()
}
}
func main(work: @escaping () -> ()) {
DispatchQueue.main.async {
work()
}
}
然后在需要的地方调用它:
background {
//background job
main {
//update UI (or what you need to do in main thread)
}
}
Swift 3.0 +
在Swift 3.0中,很多东西都被现代化了。在后台队列上运行一些东西看起来像这样:
DispatchQueue.global(qos: .userInitiated).async {
print("This is run on a background queue")
DispatchQueue.main.async {
print("This is run on the main queue, after the previous code in outer block")
}
}
Swift 1.2到2.3
let qualityOfServiceClass = QOS_CLASS_USER_INITIATED
let backgroundQueue = dispatch_get_global_queue(qualityOfServiceClass, 0)
dispatch_async(backgroundQueue, {
print("This is run on a background queue")
dispatch_async(dispatch_get_main_queue(), { () -> Void in
print("This is run on the main queue, after the previous code in outer block")
})
})
Pre Swift 1.2 -已知问题
从Swift 1.1开始,苹果在没有做一些修改的情况下不支持上述语法。传递qos_class_user_initialized实际上不起作用,而是使用Int(qos_class_user_initialized .value)。
有关更多信息,请参阅apple文档
最佳实践是定义一个可多次访问的可重用函数。
可重用的功能:
例如,AppDelegate.swift是一个全局函数。
func backgroundThread(_ delay: Double = 0.0, background: (() -> Void)? = nil, completion: (() -> Void)? = nil) {
dispatch_async(dispatch_get_global_queue(Int(QOS_CLASS_USER_INITIATED.value), 0)) {
background?()
let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
dispatch_after(popTime, dispatch_get_main_queue()) {
completion?()
}
}
}
注意:在Swift 2.0中替换QOS_CLASS_USER_INITIATED。使用QOS_CLASS_USER_INITIATED。rawValue相反
用法:
a .在后台运行一个进程,延迟3秒:
backgroundThread(3.0, background: {
// Your background function here
})
B.在后台运行一个进程,然后在前台运行一个补全:
backgroundThread(background: {
// Your function here to run in the background
},
completion: {
// A function to run in the foreground when the background thread is complete
})
C.延迟3秒-注意使用completion参数而不使用background参数:
backgroundThread(3.0, completion: {
// Your delayed function here to be run in the foreground
})