go - 如何使用第三方包中未导出的对象作为 golang 中的返回类型？

Question

在我的用例中，我使用的是 influxdb。我正在尝试在 Golang 中为 influxdb 创建一个全局客户端。但是当我从函数返回 influxdb 客户端时，客户端对象不会在 influxdb 包中导出。所以我无法返回。

这是我的代码:

package influxclient

import (
    "github.com/influxdata/influxdb/client/v2"
    "log"
    "time"
    //"net/http"
    "fmt"
    "reflect"
)

const (
    INFLUXDB_NAME = "XXXX"
    USERNAME      = "YYYY"
    PASSWORD      = "ZZZZ"
    HOST          = "http://localhost:8086"
)

var (
    c             = getHTTPClient()
)

func test() {
    // Create a new point batch
    bp, _ := client.NewBatchPoints(client.BatchPointsConfig{
        Database:  INFLUXDB_NAME,
        Precision: "s",
    })

    // Create a point and add to batch
    tags := map[string]string{"cpu": "cpu-total"}
    fields := map[string]interface{}{
        "idle":   10.1,
        "system": 53.3,
        "user":   46.6,
    }
    fmt.Println(reflect.TypeOf(c))
    pt, _ := client.NewPoint("cpu_usage", tags, fields, time.Now())
    bp.AddPoint(pt)

    // Write the batch
    c.Write(bp)
}

//publish metrics to metrics db
func PublishMetrics(metricName string, tags map[string]string, fields map[string]interface{}, time time.Time) error {
    fmt.Println("type of client c ", reflect.TypeOf(c))
    // Create a new point batch
    bp, err := client.NewBatchPoints(client.BatchPointsConfig{
        Database:  INFLUXDB_NAME,
        Precision: "s",
    })
    if err != nil {
        return err
    }
    pt, err := client.NewPoint(metricName, tags, fields, time)
    if err != nil {
        return err
    }
    bp.AddPoint(pt)
    // Write the batch
    c.Write(bp)
    return nil
}


func getHTTPClient() *client.client {
    //make http client for metrics db
    c, err := client.NewHTTPClient(client.HTTPConfig{
        Addr:     HOST,
        Username: USERNAME,
        Password: PASSWORD,
    })
    if err != nil {
        log.Printf("FATAL :: Error occured in getting influxdb metric client %s ", err.Error())
    }
    return c
}

getHTTPClient() 函数试图返回客户端对象 *client.client。
但是在influxdb golang包中并没有导出client对象。
那么我该如何处理这个问题呢？
谁能帮我解决这个问题？

谢谢

Answer 1

包客户端//import "github.com/influxdata/influxdb/client/v2"
已导出 Client 接口(interface)，因此请使用 client.Client 而不是 *client.client:

package influxclient

import (
    "log"
    "time"

    "github.com/influxdata/influxdb/client/v2"
    //"net/http"
    "fmt"
    "reflect"
)

const (
    INFLUXDB_NAME = "XXXX"
    USERNAME      = "YYYY"
    PASSWORD      = "ZZZZ"
    HOST          = "http://localhost:8086"
)

var c = getHTTPClient()

func test() {
    // Create a new point batch
    bp, _ := client.NewBatchPoints(client.BatchPointsConfig{
        Database:  INFLUXDB_NAME,
        Precision: "s",
    })

    // Create a point and add to batch
    tags := map[string]string{"cpu": "cpu-total"}
    fields := map[string]interface{}{
        "idle":   10.1,
        "system": 53.3,
        "user":   46.6,
    }
    fmt.Println(reflect.TypeOf(c))
    pt, _ := client.NewPoint("cpu_usage", tags, fields, time.Now())
    bp.AddPoint(pt)

    // Write the batch
    c.Write(bp)
}

//publish metrics to metrics db
func PublishMetrics(metricName string, tags map[string]string, fields map[string]interface{}, time time.Time) error {
    fmt.Println("type of client c ", reflect.TypeOf(c))
    // Create a new point batch
    bp, err := client.NewBatchPoints(client.BatchPointsConfig{
        Database:  INFLUXDB_NAME,
        Precision: "s",
    })
    if err != nil {
        return err
    }
    pt, err := client.NewPoint(metricName, tags, fields, time)
    if err != nil {
        return err
    }
    bp.AddPoint(pt)
    // Write the batch
    c.Write(bp)
    return nil
}

func getHTTPClient() client.Client {
    //make http client for metrics db
    c, err := client.NewHTTPClient(client.HTTPConfig{
        Addr:     HOST,
        Username: USERNAME,
        Password: PASSWORD,
    })
    if err != nil {
        log.Printf("FATAL :: Error occured in getting influxdb metric client %s ", err.Error())
    }
    return c
}