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:
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:
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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