[Golang] I want to add omitempty to the json tag of the int type field of the structure so that it will be ignored if 0 is entered.

Introduction

In golang, I want to ignore json when the value of the int type field of the structure is 0.

In other words, if you specify `ʻomitemptyin the json tag of an int type field and 0`` is entered in the value of that field, you want to ignore it.

** * Addition ** ** Is it actually more appropriate to say "null" than "ignore"? **

omitempty

I figured out how to ignore json when the struct field is empty

type User struct {
  Name string `json:"name, omitempty"`
  Age  int64  `json:"age, omitempty"`
}

However, in `ʻomitempty, the numeric type cannot be ignored even if 0`` is entered.

solution

So, if you want to use a numeric field as a pointer and ignore it, you can solve it by putting nil in the pointer.

//User structure
type User struct {
  Name string `json:"name, omitempty"`
  Age  *int64 `json:"age, omitempty"`
}

//Value to map to the structure
testName := "Alice"
testAge := 20

var age *int64
if age > 0 {
  age = &testAge
} else {
  age = nil
}

user := User {
  Name: testName,
  Age:  age,
}

If you do the above, when you make json.Marshal (user), ~~ If testAge is 0, the ʻAge`` field of the ʻUserstructure is ignored, If it is greater than 0, it will not be ignored. ~~ If testAgeis 0, then json will be "age": null When it is larger than 0, it becomes "age": 20`` and so on.

reference

-Play with JSON in go language-Qiita

• json - The Go Programming Language -How to omitempty Struct --Qiita -Pointers and addresses learned with Go --Qiita