当 *string 值为 nil 时，如何将 *string 类型的值转换/分配为

Question

我正在尝试将 type 的值分配给 type*string的变量*wrapperspb.StringValue。但是，当*string为 nil 时，它会触发错误（请查看截取代码中的注释以了解是何种错误）。

这是我的代码的简化版本：

// You can edit this code!

// Click here and start typing.

package main

import (

    "fmt"

    "google.golang.org/protobuf/types/known/wrapperspb"

)

func main() {

    var var1 *wrapperspb.StringValue

    var1 = &wrapperspb.StringValue{Value: "test1"}

    fmt.Println("var1:")

    fmt.Println(var1)

    var var2 *string

    fmt.Println("var2:")

    fmt.Println(var2)

    //var1 = var2 // it says "Cannot use 'var2' (type *string) as the type *wrapperspb.StringValue"

    //var1 = wrapperspb.String(*var2) // it says panic: runtime error: invalid memory address or nil pointer dereference

    //fmt.Println("var1 with var2 value:")

    //fmt.Println(var1)

}

有谁知道如何正确处理转换/分配？

这是一个 golang 游乐场：https ://go.dev/play/p/5JBfU0oEIC-

Answer 1

如果您的var2字符串指针是nil，您也应该保留var1 *wrapperspb.StringValue指针nil。wrapperspb.StringValue如果本身是nil指针，则句柄的方法。所以像这样“转换”它：if var2 == nil {&nbsp; &nbsp; var1 = nil} else {&nbsp; &nbsp; var1 = wrapperspb.String(*var2)}测试它：for i := 0; i < 2; i++ {&nbsp; &nbsp; var var1 *wrapperspb.StringValue&nbsp; &nbsp; var var2 *string&nbsp; &nbsp; if i == 0 {&nbsp; &nbsp; &nbsp; &nbsp; s := "test"&nbsp; &nbsp; &nbsp; &nbsp; var2 = &s&nbsp; &nbsp; }&nbsp; &nbsp; if var2 == nil {&nbsp; &nbsp; &nbsp; &nbsp; var1 = nil&nbsp; &nbsp; } else {&nbsp; &nbsp; &nbsp; &nbsp; var1 = wrapperspb.String(*var2)&nbsp; &nbsp; }&nbsp; &nbsp; fmt.Printf("var2: %v\n", var2)&nbsp; &nbsp; fmt.Printf("var1: %v\n", var1)&nbsp; &nbsp; fmt.Printf("%q\n", var1.GetValue())}这将输出（在Go Playground上尝试）：var2: 0xc00009e470var1: value:"test""test"var2: <nil>var1: <nil>""