映射未更新：映射值是固定大小的数组

Question

我在结构中有一个地图：type Neighborhood struct {    rebuilt map[uint32][3]uint32 // Facet index vs {neighbor0, neighbor1, neighbor2}}我初始化地图：    n := &Neighborhood{        rebuilt: make(map[uint32][3]uint32, 9348),    }    // Populate neighbors with default of UINT32_MAX    for i := uint32(0); i < 9348; i++ {        n.rebuilt[i] = [3]uint32{math.MaxUint32, math.MaxUint32, math.MaxUint32}    }稍后需要更新地图，但这不起作用：                nbrs0 := n.rebuilt[4]                nbrs1 := n.rebuilt[0]                nbrs0[2] = 0                nbrs1[1] = 4地图实际上并未使用上述赋值语句进行更新。我错过了什么？

Answer 1

您需要再次将数组分配给映射。

     nbrs0 := n.rebuilt[4]
     nbrs1 := n.rebuilt[0]
     nbrs0[2] = 0
     nbrs1[1] = 4
     n.rebuilt[4] = nrbs0
     n.rebuilt[0] = nrbs1

当您分配给 您时，请制作原始数组的副本。因此，更改不会传播到 map，您需要使用新数组显式更新映射。nbrsN

Answer 2

您需要将值重新分配给地图条目...

package main

import (

    "fmt"

    "math"

)

type Neighborhood struct {

    rebuilt map[uint32][3]uint32 // Facet index vs {neighbor0, neighbor1, neighbor2}

}

func main() {

    n := &Neighborhood{

        rebuilt: make(map[uint32][3]uint32, 9348),

    }

    // Populate neighbors with default of UINT32_MAX

    for i := uint32(0); i < 3; i++ {

        n.rebuilt[i] = [3]uint32{math.MaxUint32, math.MaxUint32, math.MaxUint32}

    }

    v := n.rebuilt[1]

    v[1] = uint32(0)

    fmt.Printf("%v\n", v)

    fmt.Printf("%v\n", n)

    n.rebuilt[1] = v

    fmt.Printf("%v\n", n)

}

https://play.golang.org/p/Hk5PRZlHUYc