douguanyan9928 2017-05-05 18:31
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Golang:将值分配给作为指针的struct成员

I'm trying to assign a value to a struct member that is a pointer, but it gives "panic: runtime error: invalid memory address or nil pointer dereference" at runtime...

package main

import (
    "fmt"
    "strconv"
)

// Test
type stctTest struct {
    blTest *bool
}

func main() {

    var strctTest stctTest
    *strctTest.blTest = false

    fmt.Println("Test is " + strconv.FormatBool(*strctTest.blTest))

}

The runtime error seems to come from the assignment of the value with *strctTest.blTest = false , but why? How do I set it to false?

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  • douxi8119 2017-05-05 18:40
    关注

    Why is it an error? Because a pointer only points. It doesn't create anything to point AT. You need to do that.

    How to set it to false? This all depends on WHY you made it a pointer.

    Is every copy of this supposed to point to the same bool? Then it should be allocated some space in a creation function.

    func NewStruct() *strctTest {
        bl := true
        return &strctTest{
            blTest: &bl,
         }
    }
    

    Is the user supposed to point it at a boolean of his own? Then it should be set manually when creating the object.

    func main() {
        myBool := false
        stctTest := strctTest{
            blTest: &myBool
        }
    
        fmt.Println("Test is " + strconv.FormatBool(*strctTest.blTest))
    
    }
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
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