小编A.C*_*A.C的帖子

我是go lang的新手.我想读一个excel文件以便稍后处理,但我不知道如何阅读文件？有人能告诉我一个例子吗？

我使用 docker 为一个项目编写 Vapor、PostgreSQL 和 Nginx，我的 docker-compose.yml 像这样：

version: "3.6"

services:
    vapor:
        build:
            context: ./vapor
        image: ${CURRENT_VAPOR_IMG}
        ports:
            - 8080:8080
        volumes:
            - ${HOST_ROOT}:${CONTAINER_ROOT}
        working_dir: ${CONTAINER_ROOT}
        tty: true
        entrypoint: bash
        networks:
            - x-net

    nginx:
        build:
            context: ./nginx
        image: ${CURRENT_NGINX_IMG}
        ports:
            - ${HOST_HTTP_PORT}:80
        volumes:
            - ${HOST_ROOT}:${CONTAINER_ROOT}
        networks:
            - x-net

    psql:
        image: ${CURRENT_DB_IMG}
        ports:
            - 5432:5432
        environment:
            - POSTGRES_DB=xxx
            - POSTGRES_USER=xxx
            - POSTGRES_PASSWORD=pass
        volumes:
            - ~/x/x-db:/var/lib/postgresql/data
    networks:
        - x-net

networks:
    x-net:
         driver: bridge

运行docker-compose up启动所有容器后，进入到vapor的容器中build&&运行项目，控制台会提示错误：

NIO.ChannelError.connectFailed(NIO.NIOConnectionError(host: "localhost", port: 5432, dnsAError: nil, dnsAAAAError: nil, …

尝试理解地图,并写一个来测试它,

func map<A, B>(x: A?, f: A -> B) -> B? {
  if let x1 = x {
    return f(x1)
  }
  return nil
}

let test1 = [1, 2, 3, 4]
println(test1)
let test2 = map(test1, { $0 + 1 })
println(test2)

let test3: [Int?] = [5, nil, 7, 8]
println(test3)//[{Some "aaa"}, {Some "bbb"}, nil, {Some "ccc"}]
let test4 = map(test3, { $0 + 1 })
println(test4) //"Optional(0x00007fb7ea61e190)"

但为什么test4无法输出值,只显示一个指针？