按指定字段对结构切片排序

Question

Let's say I have struct SortableStruct with 3 fields A B C I want to implement function that consumes sl []SortableStruct and orderFied string where orderField is one of struct's field. This function should retrun slice sorted by orderField. Is there a way of doing this without huge switch case. It's not ovious for me how to implement sort.Interface when I want compare structs by different fields.

Answer 1

Well, easiest way is to switch field type and assign a SORT function. Here is your code:

package main

import (
    "fmt"
    "sort"
)

type SortableStruct struct {
    A int
    B int
    C int
}

func sortStruct(arr []SortableStruct, field string) {
    var less func(i, j int) bool
    switch field {
    case "B":
        less = func(i, j int) bool {
            return arr[i].B < arr[j].B
        }
    case "C":
        less = func(i, j int) bool {
            return arr[i].C < arr[j].C
        }
    default:
        less = func(i, j int) bool {
            return arr[i].A < arr[j].A
        }
    }

    sort.Slice(arr, less)
}

func main() {
    arr := []SortableStruct{
        {
            A: 1,
            B: 5,
            C: 3,
        },
        {
            A: 2,
            B: 3,
            C: 20,
        },
        {
            A: -1,
            B: -1,
            C: 10,
        },
    }

    sortStruct(arr, "C")
    fmt.Println(arr)
}

Another idea would be to have 3 defined types, each of them implementing interface sort.Interface

type SortableStructByA []SortableStruct
type SortableStructByB []SortableStruct
type SortableStructByC []SortableStruct

And then, you will have to cast your slice to the wanted type(depending on sort you want) and to do something like this:

sortableSlice := SortableStructByA(arr)
sort.Sort(sortableSlice)