go for range 踩坑

本文链接： https://blog.csdn.net/lishuangquan1987/article/details/129102315

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错误的做法：

for _, model := range models {
			model.ProjectId = sql.NullInt32{Valid: true, Int32: int32(*projectId)}
			model.FlowId = sql.NullInt32{Valid: true, Int32: int32(flow.Id)}
		}

此时model只是一个副本

正确的做法：

for i, _ := range models {
			models[i].ProjectId = sql.NullInt32{Valid: true, Int32: int32(*projectId)}
			models[i].FlowId = sql.NullInt32{Valid: true, Int32: int32(flow.Id)}
		}

测试：

type Person1 struct {
	Name1 string
	Age1  int
}

func main() {
	persons := []Person1{
		{Name1: "tony1", Age1: 1},
		{Name1: "tony2", Age1: 2},
		{Name1: "tony3", Age1: 3},
		{Name1: "tony4", Age1: 4},
	}
	//打印
	fmt.Println(persons)
	//遍历修改值：错误的做法
	for i, p := range persons {
		p.Name1 = "tony"
		fmt.Println(p == persons[i])
	}
	fmt.Println("错误的遍历后输出值：")
	fmt.Println(persons)
	//遍历修改值：正确的做法
	for i, _ := range persons {
		persons[i].Name1 = "tony"
	}
	fmt.Println("正确的遍历后输出值：")
	fmt.Println(persons)
}

输出：

PS E:\Go Project\test20221122> go run main.go
[{tony1 1} {tony2 2} {tony3 3} {tony4 4}]
false
false
false
false
错误的遍历后输出值：
[{tony1 1} {tony2 2} {tony3 3} {tony4 4}]
正确的遍历后输出值：
[{tony 1} {tony 2} {tony 3} {tony 4}]

可以看到： fmt.Println(p == persons[i]) 这一句输出的是false