GoValid

GoValid is a lightweight validation library for Golang designed to simplify data structure validation using tags in structs. It supports built-in rules like required, min, max, and email, and allows users to define custom validation rules.

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🎯 Features

• ✅ Tag-based validation for structs.
• ✅ Built-in rules:
  • required: Ensures the field is not empty.
  • min: Minimum value for integers.
  • max: Maximum value for integers.
  • email: Validates email format.
• ✅ Support for custom rules.
• ✅ Easy-to-follow documentation and examples.

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🚀 Installation

Install the library using go get:

go get github.com/harrysan/govalid

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🔧 Usage

1. Validate Structs with Built-In Rules

Use the validate tag to define rules for your struct fields.

package main

import (
	"fmt"
	"github.com/harrysan/govalid"
)

type User struct {
	Name  string validate:"required,min=3"
	Age   int    validate:"min=18,max=99"
	Email string validate:"required,email"
}

func main() {
	user := User{
		Name:  "Jo",
		Age:   17,
		Email: "invalid-email",
	}  

	errs := govalid.ValidateStruct(user)
	if len(errs) > 0 {
		fmt.Println("Validation Errors:")
		for _, err := range errs {
			fmt.Println(err)
		}
	} else {
		fmt.Println("Validation Passed!")
	}
}

Output:

Validation Errors:
Field 'Name' failed validation 'min=3': value must be greater than or equal to 3
Field 'Age' failed validation 'min=18': value must be greater than or equal to 18
Field 'Email' failed validation 'email': invalid email format

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2. Add Custom Validation Rules

You can register custom validation rules using the RegisterCustomRule function.

package main

import (
	"fmt"
	"github.com/harrysan/govalid"
)

func main() {
	// Register a custom rule
	err := govalid.RegisterCustomRule("isEven", func(field string, value interface{}) error {
		v, ok := value.(int)
		if !ok {
			return fmt.Errorf("%s must be an integer", field)
		}
		if v%2 != 0 {
			return fmt.Errorf("%s must be an even number", field)
		}
		return nil
	})

	if err != nil {
		fmt.Println("Failed to register custom rule:", err)
		return
	}

	type Data struct {
		Number int validate:"isEven"
	}

	data := Data{Number: 3}
	errs := govalid.ValidateStruct(data)
  
	if len(errs) > 0 {
		fmt.Println("Validation Errors:")
		for _, err := range errs {
			fmt.Println(err)
		}
	} else {
		fmt.Println("Validation Passed!")
	}
}

Output:

Validation Errors:
Field 'Number' failed validation 'isEven': Number must be an even number

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📜 Built-In Rules

Rule	Description	Example Tag
required	Ensures the field is not empty.	validate:"required"
min	The field must be greater than or equal to a minimum value.	validate:"min=3"
max	The field must be less than or equal to a maximum value.	validate:"max=10"
email	The field must be in a valid email format.	validate:"email"

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⚙️ API Reference

1. ValidateStruct

func ValidateStruct(s interface{}) []ValidationError

2. RegisterCustomRule

func RegisterCustomRule(name string, rule CustomRule) error

Registers a custom validation rule with a unique name and a function that implements the rule.

3. ValidationError

Struct representing a validation error:

type ValidationError struct {
	Field string      // Name of the field that failed validation
	Tag   string      // The validation rule that failed
	Value interface{} // The value of the field that failed validation
	Err   error       // Details about the error
}

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📂 Project Structure

govalid/
├── go.mod                  		# Go module file
├── validator/
│   ├── validator.go        		# Core validation logic
│   ├── rules.go            		# Built-in validation rules
│   ├── custom.go           		# Custom validation rule support
├── test/
│   ├── example_test.go     		# Unit test for basic validation
│   ├── example_custom_test.go 		# Unit test for custom validation rules
├── README.md               		# Project documentation

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🛠️ Roadmap

Planned features for future updates:

• Support for nested struct validation.
• Customizable error messages (including multi-language support).
• Validation for additional data types (e.g., float, time).

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🤝 Contributing

Contributions are welcome! Feel free to open a pull request or report issues in the issues section.

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📄 License

This library is licensed under the MIT License.

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Happy coding ! 😊