如何编写将数组成员分配给self的方法

Question

I have an array of structs and a method for finding a struct with a given ID within that array. If it exists, I want to copy it into the struct itself. But I can't make it work.

I can make it work with Marshal and Unmarshal, but I don't think this is a good solution.

https://play.golang.org/p/16giIQ0R1Hv

package main

import (
    "fmt"
)

type Tmp struct {
    ID  int
    Val int
}

var members []Tmp

func (o *Tmp) FindID(id int) {
    for i := range members {
        if members[i].ID == id {
            fmt.Println("found!")
            fmt.Println(members[i])
            tmp := members[i]
            o = &tmp
        }
    }
}

func main() {
    for i := 0; i < 5; i++ {
        o := Tmp{ID: i, Val: i * 2}
        members = append(members, o)
    }
    fmt.Println(members)
    a := Tmp{}
    a.FindID(3)
    fmt.Println(a)
}

This outputs:

[{0 0} {1 2} {2 4} {3 6} {4 8}]
found!
{3 6}
{0 0}

Answer 1

You can use the dereference operator to assign a value to a pointer

*o = members[i]

So, in your case:

func (o *Tmp) FindID(id int) bool {
    for i := range members {
        if members[i].ID == id {
            *o := members[i]
            return true
        }
    }
    return false
}

I took the liberty to make the function indicate (via return values) whether it actually found anything or not; of course, you can ignore that change.