【Golang实战】反射设置结构体字段值

这个测试用例，是在上一篇通过反射自定义排序字段的基础上做的补充，因为在业务代码中涉及到slice排序完之后，给最小元素的字段赋值场景。

type Str struct {
	A string
	V int
}
func TestReflectMapSet(t *testing.T) {
	var ddd = map[int]*Str{
		2:  {A: "test A", V: 2},
		1:  {A: "test b", V: 1},
		-1: {A: "test c", V: -1},
	}
	tmpData := ddd[1]
    // tmpData 一定是指针类型的
	reflect.ValueOf(tmpData).Elem().FieldByName("V").SetInt(22)
	ddd[1] = tmpData
	for _, d := range ddd {
		t.Log(d)
	}
}

输出：

=== RUN   TestReflectMapSet
    TestReflectMapSet: http_test.go:183: &{test A 2}
    TestReflectMapSet: http_test.go:183: &{test b 22}
    TestReflectMapSet: http_test.go:183: &{test c -1}
--- PASS: TestReflectMapSet (0.00s)
PASS

以下是结合了通过反射自定义字段排序，以及给指定字段赋值的业务代码

type DividedDecInfo struct {
	SkuId        uint64
	CouponAmount int
}

func TestReflectSort(t *testing.T) {
	var data = map[uint64]*DividedDecInfo{
		12: {SkuId: 12, CouponAmount: 3},
		13: {SkuId: 13, CouponAmount: 4},
		34: {SkuId: 34, CouponAmount: 5},
	}
	sortByType2(data, 13, "CouponAmount")
	for _, d := range data {
		t.Log(d)
	}
}

func sortByType2(data map[uint64]*DividedDecInfo, amount int, amountObj string) {
	var (
		tmpDdi         []*DividedDecInfo
		num, tmpAmount int
	)
	for _, ddi := range data {
		tmpDdi = append(tmpDdi, ddi)
	}
	num = len(tmpDdi)
	if num >= 2 {
		// 反射排序
		sort.Slice(tmpDdi, func(i, j int) bool {
			tmp := reflect.ValueOf(tmpDdi)
			return tmp.Index(i).Elem().FieldByName(amountObj).Int() > tmp.Index(j).Elem().FieldByName(amountObj).Int()
		})
		refTmp := reflect.ValueOf(tmpDdi)
		for i := 0; i <= num-2; i++ {
			log.Println(tmpDdi[i])
			// 反射取值
			tmpAmount += int(refTmp.Index(i).Elem().FieldByName(amountObj).Int())
		}
		// 反射赋值
		tmpData := data[tmpDdi[num-1].SkuId]
		reflect.ValueOf(tmpData).Elem().FieldByName(amountObj).SetInt(int64(amount - tmpAmount))
	}
}

输出：

=== RUN   TestReflectSort
2021/02/14 22:38:30 &{34 5}
2021/02/14 22:38:30 &{13 4}
    TestReflectSort: http_test.go:215: &{12 4}
    TestReflectSort: http_test.go:215: &{13 4}
    TestReflectSort: http_test.go:215: &{34 5}
--- PASS: TestReflectSort (0.02s)
PASS