Swift

实现类似前端的async、await方法

October 23, 2020

How to make async / await in Swift? https://stackoverflow.com/questions/48713427/how-to-make-async-await-in-swift

Thanks to vadian's comment, I found what I expected, and it's pretty easy. I use DispatchGroup(), group.enter(), group.leave() and group.notify(queue: .main){}.

func myFunction() {
    let array = [Object]()
    let group = DispatchGroup() // initialize

    array.forEach { obj in

        // Here is an example of an asynchronous request which use a callback
        group.enter() // wait
        LogoRequest.init().downloadImage(url: obj.url) { (data) in
            if (data) {
                group.leave() // continue the loop
            }
        }
    }

    group.notify(queue: .main) {
        // do something here when loop finished
    }
}