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// Package validator implements value validations
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/* |
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//
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Package validator implements value validations for structs and individual fields based on tags. |
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// The MIT License (MIT)
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//
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Built In Validator |
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// Copyright (c) 2015 Dean Karn
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//
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The package contains a built in Validator instance for use, |
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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but you may also create a new instance if needed. |
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// built in
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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errs := validator.ValidateStruct(//your struct)
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// copies of the Software, and to permit persons to whom the Software is
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errs := validator.ValidateFieldByTag(field, "omitempty,min=1,max=10") |
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// furnished to do so, subject to the following conditions:
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//
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// new
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// The above copyright notice and this permission notice shall be included in all
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newValidator = validator.New("struct tag name", validator.BakedInFunctions) |
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// copies or substantial portions of the Software.
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//
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A simple example usage: |
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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type UserDetail { |
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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Details string `validate:"-"` |
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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} |
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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type User struct { |
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// SOFTWARE.
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Name string `validate:"required,max=60"` |
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PreferedName string `validate:"omitempty,max=60"` |
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Sub UserDetail |
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} |
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user := &User { |
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Name: "", |
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} |
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// errs will contain a hierarchical list of errors
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// using the StructValidationErrors struct
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// or nil if no errors exist
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errs := validator.ValidateStruct(user) |
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// in this case 1 error Name is required
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errs.Struct will be "User" |
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errs.StructErrors will be empty <-- fields that were structs |
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errs.Errors will have 1 error of type FieldValidationError |
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Error Handling |
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The error can be used like so |
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fieldErr, _ := errs["Name"] |
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fieldErr.Field // "Name"
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fieldErr.ErrorTag // "required"
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Both StructValidationErrors and FieldValidationError implement the Error interface but it's |
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intended use is for development + debugging, not a production error message. |
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fieldErr.Error() // Field validation for "Name" failed on the "required" tag
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errs.Error() |
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// Struct: User
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// Field validation for "Name" failed on the "required" tag
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Why not a better error message? because this library intends for you to handle your own error messages |
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Why should I handle my own errors? Many reasons, for me building and internationalized application |
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I needed to know the field and what validation failed so that I could provide an error in the users specific language. |
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if fieldErr.Field == "Name" { |
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switch fieldErr.ErrorTag |
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case "required": |
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return "Translated string based on field + error" |
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default: |
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return "Translated string based on field" |
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} |
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The hierarchical structure is hard to work with sometimes.. Agreed Flatten function to the rescue! |
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Flatten will return a map of FieldValidationError's but the field name will be namespaced. |
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// if UserDetail Details field failed validation
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Field will be "Sub.Details" |
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// for Name
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Field will be "Name" |
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Custom Functions |
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Custom functions can be added |
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//Structure
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func customFunc(field interface{}, param string) bool { |
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if whatever { |
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return false |
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} |
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return true |
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} |
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validator.AddFunction("custom tag name", customFunc) |
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// NOTE: using the same tag name as an existing function
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// will overwrite the existing one
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Custom Tag Name |
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A custom tag name can be set to avoid conficts, or just have a shorter name |
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validator.SetTag("valid") |
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Multiple Validators |
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Multiple validators on a field will process in the order defined |
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type Test struct { |
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Field `validate:"max=10,min=1"` |
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} |
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// max will be checked then min
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Bad Validator definitions are not handled by the library |
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type Test struct { |
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Field `validate:"min=10,max=0"` |
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} |
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// this definition of min max will never validate
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Baked In Validators |
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Here is a list of the current built in validators: |
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- |
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Tells the validation to skip this struct field; this is particularily |
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handy in ignoring embedded structs from being validated. (Usage: -) |
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omitempty |
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Allows conitional validation, for example if a field is not set with |
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a value (Determined by the required validator) then other validation |
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such as min or max won't run, but if a value is set validation will run. |
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(Usage: omitempty) |
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len |
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For numbers, max will ensure that the value is |
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equal to the parameter given. For strings, it checks that |
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the string length is exactly that number of characters. For slices, |
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arrays, and maps, validates the number of items. (Usage: len=10) |
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max |
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For numbers, max will ensure that the value is |
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less than or equal to the parameter given. For strings, it checks |
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that the string length is at most that number of characters. For |
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slices, arrays, and maps, validates the number of items. (Usage: max=10) |
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min |
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For numbers, min will ensure that the value is |
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greater or equal to the parameter given. For strings, it checks that |
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the string length is at least that number of characters. For slices, |
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arrays, and maps, validates the number of items. (Usage: min=10) |
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required |
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This validates that the value is not the data types default value. |
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For numbers ensures value is not zero. For strings ensures value is |
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not "". For slices, arrays, and maps, ensures the length is not zero. |
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(Usage: required) |
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Validator notes: |
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regex |
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a regex validator won't be added because commas and = signs can be part of |
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a regex which conflict with the validation definitions, although workarounds |
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can be made, they take away from using pure regex's. Furthermore it's quick |
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and dirty but the regex's become harder to maintain and are not reusable, so |
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it's as much as a programming philosiphy as anything. |
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In place of this new validator functions should be created; a regex can be |
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used within the validator function and even be precompiled for better efficiency. |
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And the best reason, you can sumit a pull request and we can keep on adding to the |
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validation library of this package! |
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Panics |
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This package panics when bad input is provided, this is by design, bad code like that should not make it to production. |
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type Test struct { |
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TestField string `validate:"nonexistantfunction=1"` |
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} |
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t := &Test{ |
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TestField: "Test" |
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} |
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validator.ValidateStruct(t) // this will panic
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*/ |
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package validator |
package validator |
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