Go Validators

A powerful, lightweight, and dependency-free validation package for Go.
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Table of Contents

• About The Project
• Features
• Built With
• Getting Started
• Execution Order
• Usage
• Available Validators
• Contributing
• License
• Author

About The Project

Go Validators is a validation package for Go designed to be powerful, lightweight, and dependency-free. It provides a flexible way to handle data validation, allowing developers to declaratively validate structs from JSON payloads using validates tags or use individual validation functions for granular control.

This package is easily integrated into any Go project without introducing external dependencies, offering a simple yet extensible solution for ensuring data integrity.

Features

• Struct Validation: Declaratively validate structs from JSON payloads using validates tags.
• Standalone Functions: Use individual validation functions for granular control over any value.
• Zero Dependencies: A lightweight package that can be integrated into any project without external dependencies.
• Customizable: Extend the library with your own logic using the Custom validator.

Built With

This project was developed using the following core technologies:

• Go – An open-source programming language designed for simplicity, reliability, and efficiency in building scalable software.

Getting Started

To get a local copy up and running, follow these steps.

Installation

go get github.com/dariomatias-dev/go-validators

Execution Order

Validators should be organized in a three-stage order within validates tags:

1. Presence Validators (required): Confirm the field exists.
2. Type Validators (isString, isInt, etc.): Ensure the value has the correct data type.
3. Value Validators (minLength, email, etc.): Apply specific rules to the value's content.

This order prevents runtime errors by ensuring that value validators never receive an unexpected type.

Usage

Import the package using an alias for cleaner code:

import v "github.com/dariomatias-dev/go-validators"

Struct Validation (via Tags)

Validate a JSON payload by mapping it to a struct with validates tags. The Validate function returns a map of errors or nil on success.

type UserModel struct {
    Name  string `json:"name"  validates:"required;isString;minLength=3;maxLength=20"`
    Age   int    `json:"age"   validates:"required;isInt;min=18;max=100"`
    Email string `json:"email" validates:"required;email"`
}

user := UserModel{}

jsonPayload := `{
    "name":  "Name",
    "age":   16,
    "email": "emailexample@gmail.com"
}`

err := v.Validate(&user, jsonPayload)
if err != nil {
    fmt.Println(err)
    return
}

Standalone Validation

Validators are configurable higher-order functions. The first parentheses configure the rule, the second receives the value.

value := 4
err, _ := v.Min(3, "Value must be at least 3.")(value)
if err != nil {
    fmt.Println(err)
}

value = 2
err, _ = v.Min(3)(value)
if err != nil {
    fmt.Println(err)
    return
}

Available Validators

All parameters marked with (*) are mandatory. Custom error messages are always optional.

Validator	Category	Parameters	Applicable Value Type
Required	Presence		any
IsString	Type		string
IsNumber	Type		int, float
IsInt	Type		int
IsFloat	Type		float
IsBool	Type		bool
IsArray	Type	field validators string*	slice, array
IsNullString	Type		nil, string
IsNullNumber	Type		nil, int, float
IsNullInt	Type		nil, int
IsNullFloat	Type		nil, float
IsNullBool	Type		nil, bool
IsNullArray	Type	field validators string*	nil, slice, array
Email	Value		string
Password	Value		string
Min	Value	minimum value (number)*	int, int32, int64, float32, float64
Max	Value	maximum value (number)*	int, int32, int64, float32, float64
Length	Value	size int*	string, slice, array
MinLength	Value	minimum size int*	string, slice, array
MaxLength	Value	maximum size int*	string, slice, array
IsAlpha	Value		string
IsAlphaNum	Value		string
IsAlphaSpace	Value		string
IsAlphaNumSpace	Value		string
StartsWith	Value	prefix string*	string
StartsNotWith	Value	prefix string*	string
EndsWith	Value	suffix string*	string
EndsNotWith	Value	suffix string*	string
Regex	Value	regex string*	string
Url	Value		string
Uuid	Value	version int (Default: 5)	string
OneOf	Value	options []string*	string
Custom	Value	custom validator function*	any

Contributing

Contributions make the open-source community an amazing place to learn, inspire, and create. Any contributions you make are greatly appreciated.

1. Fork the Project
2. Create your Feature Branch

git checkout -b feature/AmazingFeature

3. Commit your Changes

git commit -m 'Add some AmazingFeature'

4. Push to the Branch

git push origin feature/AmazingFeature

5. Open a Pull Request

License

Distributed under the MIT License. See the LICENSE file for more information.

Author

Developed by Dário Matias:

• Portfolio: dariomatias-dev
• GitHub: dariomatias-dev
• Email: matiasdario75@gmail.com
• Instagram: @dariomatias_dev
• LinkedIn: linkedin.com/in/dariomatias-dev