在语言版本3中进行更改后, Swift中dispatch_once的新语法是什么？旧版本如下. var token: dispatch_once_t = 0func test() { dispatch_once(token) { }} 制作了这些are the changes to libdispatch. 从 doc： Dispatch The f
var token: dispatch_once_t = 0
func test() {
dispatch_once(&token) {
}
}
制作了这些are the changes to libdispatch.
从 doc：Dispatch
The free function dispatch_once is no longer available in
Swift. In Swift, you can use lazily initialized globals or static
properties and get the same thread-safety and called-once guarantees
as dispatch_once provided. Example:
let myGlobal = { … global contains initialization in a call to a closure … }()
_ = myGlobal // using myGlobal will invoke the initialization code only the first time it is used.