Package validator

Package validator implements value validations for structs and individual fields based on tags.

It has the following unique features:

• Cross Field and Cross Struct validations by using validation tags or custom validators.
• Slice, Array and Map diving, which allows any or all levels of a multidimensional field to be validated.
• Ability to dive into both map keys and values for validation
• Handles type interface by determining it's underlying type prior to validation.
• Handles custom field types such as sql driver Valuer and the Valuer interface
• Alias validation tags, which allows for mapping of several validations to a single tag for easier defining of validations on structs
• Extraction of custom defined Field Name e.g. can specify to extract the JSON name while validating and have it available in the resulting FieldError
• Customizable i18n aware error messages.
• Default validator for the gin web framework; upgrading from v8 to v9 in gin see here

A Call for Maintainers

Please read the discussion started here if you are interested in contributing/helping maintain this package.

Installation

Use go get.

go get github.com/go-playground/validator/v10

Then import the validator package into your own code.

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

Error Return Value

Validation functions return type error

They return type error to avoid the issue discussed in the following, where err is always != nil:

• http://stackoverflow.com/a/29138676/3158232
• https://github.com/go-playground/validator/issues/134

Validator returns only InvalidValidationError for bad validation input, nil or ValidationErrors as type error; so, in your code all you need to do is check if the error returned is not nil, and if it's not check if error is InvalidValidationError ( if necessary, most of the time it isn't ) type cast it to type ValidationErrors like so:

err := validate.Struct(mystruct)
var validationErrors validator.ValidationErrors
errors.As(err, &validationErrors)

Usage and documentation

Please see https://pkg.go.dev/github.com/go-playground/validator/v10 for detailed usage docs.

Examples:

• Simple
• Custom Field Types
• Struct Level
• Translations & Custom Errors
• Gin upgrade and/or override validator
• wash - an example application putting it all together

Baked-in Validations

Special Notes:

• If new to using validator it is highly recommended to initialize it using the WithRequiredStructEnabled option which is opt-in to new behaviour that will become the default behaviour in v11+. See documentation for more details.

validate := validator.New(validator.WithRequiredStructEnabled())

Fields:

Tag	Description
eqcsfield	Field Equals Another Field (relative)
eqfield	Field Equals Another Field
fieldcontains	Check the indicated characters are present in the Field
fieldexcludes	Current field does not contain another field's value
gtcsfield	Field Greater Than Another Relative Field
gtecsfield	Field Greater Than or Equal To Another Relative Field
gtefield	Field Greater Than or Equal To Another Field
gtfield	Field Greater Than Another Field
ltcsfield	Less Than Another Relative Field
ltecsfield	Less Than or Equal To Another Relative Field
ltefield	Less Than or Equal To Another Field
ltfield	Less Than Another Field
necsfield	Field Does Not Equal Another Field (relative)
nefield	Field Does Not Equal Another Field

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