你好，
我想保留 REST API 服务器以 JSON 发来的 null。目前我把它反序列化到结构体，这会把那些 Null 变成零值。
有人能给一个小示例或有用的视频链接吗？我尝试过指针，但没理解它的好处，因为还是看到了零值。
Hello,
I want to preserve nulls arriving as JSON from a REST API server. At the moment I unmarshal into a struct, which changes those Nulls to zero values.
Could somebody share a small example or a helpful video link? I've attempted pointers without grasping their benefit, since the zero values still appear.
type record struct {
Count *int `json:"foo"`
}你好 fernvale_54，
正如 mossglen_55 已经指出的，可以用指针表示一个值，说明对应的数据可能不存在
type Entry struct {
Text *string `json:"bar"`
}使用可能为 null 的值时，先检查它是不是 null，再把它当作实际存在的值使用，否则运行时会报 panic: runtime error: invalid memory address or nil pointer dereference，可以采用类似下面的写法，
var entry Entry
//...unmarsal into Entry
if entry.Text != nil {
// len() is safe in this branch
fmt.Println(len(*entry.Text))
}要让输出的 JSON 更整洁，也可以研究 omitempty 和 omitzero 标签(omitzero 是 go 1.24 才加入的，还比较新，因此相关资料可能不多)
Hi fernvale_54,
As mossglen_55 already pointed out, you can represent a value with a pointer to indicate that the corresponding data might be absent
type Entry struct {
Text *string `json:"bar"`
}When using a value which could possibly be null, remember to check for null before treating that value as one that actually exists, or you'll hit panic: runtime error: invalid memory address or nil pointer dereference, something along these lines works:
var entry Entry
//...unmarsal into Entry
if entry.Text != nil {
// len() is safe in this branch
fmt.Println(len(*entry.Text))
}For tidier JSON output, also investigate the omitempty and omitzero tags (omitzero arrived with go 1.24 and is fairly recent, so information about it might still be sparse)
go 有个方便的特点，len() 是一个静态函数。获取切片长度，甚至遍历切片之前，都不需要检查 null。对大多数操作来说，nil 切片的行为就像长度为 0 的切片。
不过，对于其余基本类型、结构体和映射，你说的是对的。
One pleasant feature of go is that len() is static. Before taking a slice's length, or even iterating through it, a null check isn't necessary. For most operations, a nil-slice acts as though its length were 0.
For the remaining primitives, structs and maps, however, your point stands.
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