错误：不能进行字符串和nil值的操作

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我正在尝试创建一个连接到 google cloud api 的 go restful api。

正在发生问题，描述为： 无效操作：req.parentid != nil（字符串和nil类型不匹配）

在创建本地 api 之前，我设法编写了一个 go 模块，可以连接、验证并从 google cloud 提取数据。我现在正在将该模块迁移为带有路径的 restful api。

该模块的重点是获取所有当前正在运行的虚拟机的列表。

这是将其更改为 restful api 之前的模块（有效）：

package main

import (
    "fmt"

    "example.com/compute"

    "bytes"
)

func main() {
    buf := new(bytes.buffer)

    // get a message and print it.
    r.handlefunc("/virtualmachines", listallinstances)
    err := compute.listallinstances(buf, "unique-string-id")
    if err != nil {
        panic(err)
    }
    fmt.println(buf.string()) // <======= print buf contents!
}


// new file:

package compute

// [start compute_instances_list_all]
import (
    "context"
    "fmt"
    "io"

    compute "cloud.google.com/go/compute/apiv1"
    "google.golang.org/api/iterator"
    computepb "google.golang.org/genproto/googleapis/cloud/compute/v1"
    "google.golang.org/protobuf/proto"
)

// listallinstances prints all instances present in a project, grouped by their zone.
func listallinstances(w io.writer, projectid string) error {
    // projectid := "your_project_id"
    ctx := context.background()
    instancesclient, err := compute.newinstancesrestclient(ctx)


    if err != nil {
        return fmt.errorf("newinstancesrestclient: %v", err)
    }
    defer instancesclient.close()

    // use the `maxresults` parameter to limit the number of results that the api returns per response page.
    req := &computepb.aggregatedlistinstancesrequest{
        project:    projectid,
        maxresults: proto.uint32(6),
    }

    it := instancesclient.aggregatedlist(ctx, req)
    fmt.fprintf(w, "instances found:\n")
    // despite using the `maxresults` parameter, you don't need to handle the pagination
    // yourself. the returned iterator object handles pagination
    // automatically, returning separated pages as you iterate over the results.

    for {
        pair, err := it.next()
        if err == iterator.done {
            break
        }
        if err != nil {
            return err
        }
        instances := pair.value.instances
        if len(instances) > 0 {
            fmt.fprintf(w, "%s\n", pair.key)
            for _, instance := range instances {
                fmt.fprintf(w, "- %s %s\n", instance.getname(), instance.getmachinetype())
            }
        }
    }

    return nil
}

上面的效果很好，尽管它可能不那么漂亮。

以下是我将模块移动/转换为 restful api 的努力：

package handlers

import (
    "context"
    "fmt"
    "net/http"

    compute "cloud.google.com/go/compute/apiv1"
    "google.golang.org/api/iterator"
    computepb "google.golang.org/genproto/googleapis/cloud/compute/v1"
    "google.golang.org/protobuf/proto"
)

// use google cloud compute api to get the list of instance virtual machine instances
func (s *server) getlistallinstances(w http.responsewriter, r *http.request) error {

    ctx := context.background()
    instancesclient, err := compute.newinstancesrestclient(ctx)

    if err != nil {
        return fmt.errorf("newinstancesrestclient: %v", err)
    }
    defer instancesclient.close()

    // use the `maxresults` parameter to limit the number of results that the api returns per response page.
    req := &computepb.aggregatedlistinstancesrequest{
        project:    "unqie-string-id",
        maxresults: proto.uint32(16),
    }

    it := instancesclient.aggregatedlist(ctx, req)
    fmt.fprintf(w, "instances found:\n")
    // despite using the `maxresults` parameter, you don't need to handle the pagination
    // yourself. the returned iterator object handles pagination
    // automatically, returning separated pages as you iterate over the results.

    for {
        pair, err := it.next()
        if err == iterator.done {
            break
        }
        if err != nil {
            return err
        }
        instances := pair.value.instances
        if len(instances) > 0 {
            w.writeheader(http.statusok)
            fmt.fprintf(w, "%s\n", pair.key)
            for _, instance := range instances {
                fmt.fprintf(w, "- %s %s\n", instance.getname(), instance.getmachinetype())
            }
        }
    }

    return nil

}

parentid 是罪魁祸首（滚动到下面查看完整错误）。我插入的字符串在上面的代码中似乎不起作用。 google cloud api 正在尝试找出该项目的父 id。 如何修复上面的代码？

我将这段代码留在下面仅供参考

这是我的 api 用于拉取活动虚拟机列表的路径

package handlers

import "skeleton/api/middlewares"

func (s *server) initializeroutes() {

    s.router.handlefunc("/compute", middlewares.middlewaresjson(s.getlistallinstances)).methods("get")

}

这是我的 middlewaresjson：

package middlewares

import (
    "log"
    "net/http"
)

// intercept the incoming request, and set one of the headers to content-type: application/json
func middlewaresjson(next http.handlerfunc) http.handlerfunc {
    return func(w http.responsewriter, r *http.request) {
        // log the route and method
        log.println("== route: " + r.url.path)
        log.println("== method: " + r.method)

        // modify the header
        w.header().set("content-type", "application/json")
        next(w, r)
    }
}

这是完整的错误：

cloud.google.com/go/compute/apiv1
..\go\pkg\mod\cloud.google.com\[email protected]\compute\apiv1\firewall_policies_client.go:684:32: invalid operation: req.parentid != nil (mismatched typen: req.parentid != nil (mismatched types string and nil)

以下是库中也引用错误的代码：

    if req != nil && req.ParentId != nil {
        params.Add("parentId", fmt.Sprintf("%v", req.GetParentId()))
    }

正确答案

我遇到了同样的问题，通过降级 1 次提交解决了：

go get google.golang.org/genproto@81c1377

https://github.com/googleapis/go-genproto/commits/main

这是您的代码中的错误还是只是发布中的错误？ 在出版物中我看到

req := &computepb.aggregatedlistinstancesrequest{
        project:    "unqie-string-id,
        maxresults: proto.uint32(16),
    }

但应该是

req := &computepb.AggregatedListInstancesRequest{
        Project:    "unqie-string-id",
        MaxResults: proto.Uint32(16),
    }

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