ProtoBuf的Golang解析

Question

我是Golang的新手，我正试图用Golang编写一个家庭自动化框架，使用Micro和Protobuf框架。

目前，我很难实现一个简单的注册表类型服务。

我遇到的一个问题是，如果客户端向http://localhost:8080/view/devices发出get请求，我希望能够获得设备列表

我有以下的原型定义：

syntax = "proto3";

service DRegistry {
    rpc View(ViewRequest) returns (DeviceRegistry) {}
} 

message DeviceRegistry {
    repeated Device devices = 1;
}

message ViewRequest {
    string Alias = 1;
}

message Device {
    string Alias = 1;
    string HWAddress = 2;
    string WakeUpMethod = 3;
    repeated string BoundServices = 4;
}

在我的服务定义中，我有以下几点：

package main

import (
    "log"

    micro "github.com/micro/go-micro"
    proto "github.com/srizzling/gotham/proto/device"

    "golang.org/x/net/context"
)

// DRegistry stands for Device Registry and is how devices register to Gotham.
type DRegistry struct{}

var devices map[string]proto.Device

func (g *DRegistry) View(ctx context.Context, req *proto.ViewRequest, rsp *proto.DeviceRegistry) error {
    filter := req.Alias
devices, err := filterDevices(filter)
rsp.Devices = devices
}

func filterDevices(filter string) (*[]proto.Device, error) {
    // Currently only supports listing a single service for now
    // TODO: expand filter to be more consise
    filteredDevices := make([]proto.Device, 0, len(devices))
    for _, e := range devices {
        for _, f := range e.BoundServices {
            if f == filter {
                filteredDevices = append(filteredDevices, e)
            }
        }
    }
    return &filteredDevices, nil
}

func main() {
    service := micro.NewService(
        micro.Name("DRegistry"),
    )
    proto.RegisterDRegistryHandler(service.Server(), new(DRegistry))

    if err := service.Run(); err != nil {
        log.Fatal(err)
    }
}

我遇到的问题是，我的IDE (Visual )与我的cannot use devices (type *[]device.Device) as type []*device.Device in assignment兼容，这让人感到困惑。

如何将proto.Devices的集合分配给proto.DeviceRegistry？

Answer 1

func filterDevices(filter string) ([]*proto.Device, error) {
    // Currently only supports listing a single service for now
    // TODO: expand filter to be more consise
    filteredDevices := make([]*proto.Device, 0, len(devices))
    for _, e := range devices {
        for _, f := range e.BoundServices {
            if f == filter {
                filteredDevices = append(filteredDevices, &e)
            }
        }
    }
    return filteredDevices, nil
}

指针片([]*)和指向片(*[])的指针之间有区别。您正在返回一个指针到切片，而您想要的是一段指针。我们可以通过以下方式解决这一问题：

• 更新filterDevices签名以返回指针片段
• 更新make调用以生成指针片段
• 将调用中的e地址作为附加地址(我们需要一段指向设备的指针)
• 不返回片的地址