How to use required_if when checking if a field equals a string with spaces in it?

[geoff-maddock]

I'm trying to use required_if to validate requiring a field if another field equals a specific string that has a space in it. However, I can't determine the correct format for the expression. Here are the examples I've tried and the results. In every case Churn Reason is nil:

        Stage                           *string
	ChurnReason               *string              `json:"churn_reason,omitempty" validate:"required_if=stage 'Churn Reason'"`

This succeeds, no validation error - there should be an error since Churn Reason is required and it is not provided.

        Stage                           *string
	ChurnReason               *string              `json:"churn_reason,omitempty" validate:"required_if=stage \"Churn Reason\""`

This returns an error Bad param number for required_if ChurnReason

        Stage                           *string
	ChurnReason               *string              `json:"churn_reason,omitempty" validate:"required_if=stage Churn Reason"`

This returns an error Bad param number for required_if ChurnReason

[zemzale]

In this case, you have to use the Hex code of the space which is 0x20. So that would look something like

Stage         *string
ChurnReason   *string  `validate:"required_if=stage Churn0x20Reason"`

See the docs : https://pkg.go.dev/github.com/go-playground/validator/v10#hdr-Using_Validator_Tags

[fiendish]

I also had this question, and I think the above answer is wrong. You want single quotes, and the problem is actually that the validator was using lowercase "stage" instead of uppercase "Stage".

package main

import (
	"encoding/json"
	"fmt"
	"log"

	"github.com/go-playground/validator/v10"
)

type BadValidators1 struct {
	Stage       *string
	ChurnReason *string `validate:"required_if=stage 'Churn Reason'"`  // lowercase s with single quotes
}

type BadValidators2 struct {
	Stage       *string
	ChurnReason *string `validate:"required_if=stage Churn0x20Reason"`  // lowercase s with 0x20
}

type BadValidators3 struct {
	Stage       *string
	ChurnReason *string `validate:"required_if=Stage Churn0x20Reason"`  // uppercase S with 0x20
}

type GoodValidators struct {
	Stage       *string
	ChurnReason *string `validate:"required_if=Stage 'Churn Reason'"`  // uppercase S with single quotes
}

func main() {
	jsonData := []byte(`{"stage": "Churn Reason"}`)

	var badTest1 BadValidators1
	_ = json.Unmarshal(jsonData, &badTest1)
	validateAndPrint(badTest1)

	var badTest2 BadValidators2
	_ = json.Unmarshal(jsonData, &badTest2)
	validateAndPrint(badTest2)

	var badTest3 BadValidators3
	_ = json.Unmarshal(jsonData, &badTest3);
	validateAndPrint(badTest3)

	var goodTest GoodValidators
	_ = json.Unmarshal(jsonData, &goodTest)
	validateAndPrint(goodTest)
}

func validateAndPrint(v interface{}) {
	validate := validator.New()
	err := validate.Struct(v)
	if err != nil {
		fmt.Println(err)
	} else {
		fmt.Println("No errors")
	}
}

No errors
No errors
No errors
Key: 'GoodValidators.ChurnReason' Error:Field validation for 'ChurnReason' failed on the 'required_if' tag

Program exited.

Now what you need to do for a string that has a single quote in it, I have no idea.

[nodivbyzero]

I don't know all the magic behind validators, but as a workaround, you can create a custom validator like this:

type FooBar struct {
	Stage       *string
	ChurnReason *string `validate:"churnValidation"`
}

func main() {
	validate := validator.New()
	validate.RegisterValidation("churnValidation", ValidateChurnReason)

	var foo FooBar
	goodJsonData := []byte(`{"Stage": "Churn Reason", "ChurnReason":"foobar"}`)
	_ = json.Unmarshal(goodJsonData, &foo)

	err := validate.Struct(foo)
	fmt.Printf("Validation Error(goodJsonData): %v\n", err)

	badJsonData := []byte(`{"Stage": "foobar", "ChurnReason":"xyz"}`)
	_ = json.Unmarshal(badJsonData, &foo)

	err = validate.Struct(foo)
	fmt.Printf("Validation Error(badJsonData): %v\n", err)
}

func ValidateChurnReason(fl validator.FieldLevel) bool {
	stageFld := fl.Parent().FieldByName("Stage")
	if !stageFld.IsNil() {
		goodValues := []string{"Churn Reason", "ChurnReason", "Another Churn Reason", "stage one"}

		stageValPtr := (*string)(unsafe.Pointer(stageFld.Pointer()))
		return slices.Contains(goodValues, *stageValPtr)

	}
	return false
}

and the output/result is :

Validation Error(goodJsonData): <nil>
Validation Error(badJsonData): Key: 'FooBar.ChurnReason' Error:Field validation for 'ChurnReason' failed on the 'churnValidation' tag