结合F＃异步功能(Combining F# async functions)

结合F＃异步功能(Combining F# async functions)

我在这里有点沮丧。 我知道我已经掌握了所有的东西，但我无法弄清楚如何将它们结合起来......

let saveImageToDisk path content = async { use s = new FileStream(path, FileMode.OpenOrCreate) do! s.AsyncWrite(content) printfn "Done writing %A" path } // returns Async<unit> let getImages imageUrls = imageUrls |> Seq.map (fun url -> topath url, getImage url) //Next line not happy because content is Async<byte[]> instead of byte[] |> Seq.map (fun (path, content) -> saveImageToDisk path content) |> Async.Parallel |> Async.RunSynchronously

I'm a bit frustrated here. I know I've got all the bits, but I can't work out how to combine them...

let saveImageToDisk path content = async { use s = new FileStream(path, FileMode.OpenOrCreate) do! s.AsyncWrite(content) printfn "Done writing %A" path } // returns Async<unit> let getImages imageUrls = imageUrls |> Seq.map (fun url -> topath url, getImage url) //Next line not happy because content is Async<byte[]> instead of byte[] |> Seq.map (fun (path, content) -> saveImageToDisk path content) |> Async.Parallel |> Async.RunSynchronously

最满意答案

您可以使用async表达式将两者结合使用：

let getImages imageUrls = imageUrls |> Seq.map (fun url -> async { let! content = getImage url return! saveImageToDisk (topath url) content }) |> Async.Parallel |> Async.RunSynchronously

You can combine the two using the async expression:

let getImages imageUrls = imageUrls |> Seq.map (fun url -> async { let! content = getImage url return! saveImageToDisk (topath url) content }) |> Async.Parallel |> Async.RunSynchronously