Vfrdtyky

There is struct of MyStruct.

type MyStruct struct {

    Code        int   `json:"Code"`

    Flags       uint8 `json:"Flags"`

    OptionField int   `json:",omitempty"`

}

Following code convert it to json.

f := MyStruct{Code:500, OptionField:41}

r, _ := json.Marshal(f)

fmt.Println(string(r)

I need to "OptionField" be optional. Some time it should exist in json with one of values [0, 1, 2, 3, ]. and in the other time it should exclude from json.

My problem is: omitempty will exclude it when the value is zero, and the default value of int is zero. Is there any way to omit field in condition (ex: omit if value is -1). Or there is any way to do it.

You could use *int instead of int and set the pointer value to nil in order to omit this.

package main



import (

    "encoding/json"

    "fmt"

)



type MyStruct struct {

    Code        int   `json:"Code"`

    Flags       uint8 `json:"Flags"`

    OptionField *int  `json:",omitempty"`

}



func format(s MyStruct) string {

    r, _ := json.Marshal(s)

    return string(r)

}



func main() {

    f := MyStruct{Code: 500, Flags: 10, OptionField: new(int)}

    fmt.Println(format(f)) // {"Code":500,"Flags":10,"OptionField":0}

    f.OptionField = nil

    fmt.Println(format(f)) // {"Code":500,"Flags":10}

}