muonsoft / validation

import (

	"fmt"

	"regexp"

	"github.com/muonsoft/validation"

	"github.com/muonsoft/validation/it"

	"github.com/muonsoft/validation/validator"

)

type NumericConstraint struct {

	matcher *regexp.Regexp

}

// it is recommended to use semantic constructors for constraints.

func IsNumeric() NumericConstraint {

	return NumericConstraint{matcher: regexp.MustCompile("^[0-9]+$")}

}

func (c NumericConstraint) SetUp(scope *validation.Scope) error {

	// you may return errors here on the constraint initialization process

	return nil

}

func (c NumericConstraint) ValidateString(value *string, scope validation.Scope) error {

	// usually, you should ignore empty values

	// to check for an empty value you should use it.NotBlankConstraint

	if value == nil || *value == "" {

		return nil

	}

	if c.matcher.MatchString(*value) {

		return nil

	}

	// use the scope to build violation with translations

	return scope.BuildViolation("notNumeric", "This value should be numeric.").GetViolation()

}

func ExampleValidator_Validate_customConstraint() {

	s := "alpha"

	err := validator.Validate(

		validation.String(&s, it.IsNotBlank(), IsNumeric()),

	)

	violations := err.(validation.ViolationList)

	for _, violation := range violations {

		fmt.Println(violation.Error())

	}

	// Output:

	// violation: This value should be numeric.

}