Nimlang：异步程序无法编译

Question

我正在尝试编写一个 HTTP 服务器来发送 HTTP 请求和 returns 内容到客户端。

代码如下：

import asynchttpserver, asyncdispatch
import httpClient

let client = newHttpClient()

var server = newAsyncHttpServer()

proc cb(req: Request) {.async.} =

  let content = client.getContent("http://google.com")
  await req.respond(Http200, content)

waitFor server.serve(Port(8080), cb)

但是，我得到以下编译错误信息（nim v1.0.0）：

Error: type mismatch: got <AsyncHttpServer, Port, proc (req: Request): Future[system.void]{.locks: <unknown>.}>
but expected one of:
proc serve(server: AsyncHttpServer; port: Port;
          callback: proc (request: Request): Future[void] {.closure, gcsafe.};
          address = ""): owned(Future[void])
  first type mismatch at position: 3
  required type for callback: proc (request: Request): Future[system.void]{.closure, gcsafe.}
  but expression 'cb' is of type: proc (req: Request): Future[system.void]{.locks: <unknown>.}
  This expression is not GC-safe. Annotate the proc with {.gcsafe.} to get extended error information.

expression: serve(server, Port(8080), cb)

服务函数需要另一个表达式，但不知道如何修复它。令人惊讶的是，当我从服务器回调 "cb" 中删除 HTTP 请求时，代码编译得非常好。这是否意味着服务函数需要不同的回调表达式，具体取决于回调主体？

Answer 1

好的，问题是 HttpClient 是一个全局变量，用于回调函数 "cb"。因此，回调函数不是 GC 安全的。

所以在回调函数中实例化 HttpClient 就足够了:

import asynchttpserver, asyncdispatch
import httpClient



var server = newAsyncHttpServer()

proc cb(req: Request) {.async.} =

  let client = newHttpClient()

  let content = client.getContent("https://google.com")

  await req.respond(Http200, content)

waitFor server.serve(Port(8080), cb)

Nimlang：异步程序无法编译

Nimlang: Async program does not compile

client

http

server

nim-lang