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💯Go Struct and Field validation, including Cross Field, Cross Struct, Map, Slice and Array diving
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/*
Package validator implements value validations for structs and individual fields
based on tags.
It can also handle Cross-Field and Cross-Struct validation for nested structs
and has the ability to dive into arrays and maps of any type.
see more examples https://github.com/go-playground/validator/tree/v9/_examples
Validation Functions Return Type error
Doing things this way is actually the way the standard library does, see the
file.Open method here:
https://golang.org/pkg/os/#Open.
The authors 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 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.(validator.ValidationErrors).
Custom Validation Functions
Custom Validation functions can be added. Example:
// Structure
func customFunc(fl FieldLevel) bool {
if fl.Field().String() == "invalid" {
return false
}
return true
}
validate.RegisterValidation("custom tag name", customFunc)
// NOTES: using the same tag name as an existing function
// will overwrite the existing one
Cross-Field Validation
Cross-Field Validation can be done via the following tags:
- eqfield
- nefield
- gtfield
- gtefield
- ltfield
- ltefield
- eqcsfield
- necsfield
- gtcsfield
- gtecsfield
- ltcsfield
- ltecsfield
If, however, some custom cross-field validation is required, it can be done
using a custom validation.
Why not just have cross-fields validation tags (i.e. only eqcsfield and not
eqfield)?
The reason is efficiency. If you want to check a field within the same struct
"eqfield" only has to find the field on the same struct (1 level). But, if we
used "eqcsfield" it could be multiple levels down. Example:
type Inner struct {
StartDate time.Time
}
type Outer struct {
InnerStructField *Inner
CreatedAt time.Time `validate:"ltecsfield=InnerStructField.StartDate"`
}
now := time.Now()
inner := &Inner{
StartDate: now,
}
outer := &Outer{
InnerStructField: inner,
CreatedAt: now,
}
errs := validate.Struct(outer)
// NOTE: when calling validate.Struct(val) topStruct will be the top level struct passed
// into the function
// when calling validate.VarWithValue(val, field, tag) val will be
// whatever you pass, struct, field...
// when calling validate.Field(field, tag) val will be nil
Multiple Validators
Multiple validators on a field will process in the order defined. Example:
type Test struct {
Field `validate:"max=10,min=1"`
}
// max will be checked then min
Bad Validator definitions are not handled by the library. Example:
type Test struct {
Field `validate:"min=10,max=0"`
}
// this definition of min max will never succeed
Using Validator Tags
Baked In Cross-Field validation only compares fields on the same struct.
If Cross-Field + Cross-Struct validation is needed you should implement your
own custom validator.
Comma (",") is the default separator of validation tags. If you wish to
have a comma included within the parameter (i.e. excludesall=,) you will need to
use the UTF-8 hex representation 0x2C, which is replaced in the code as a comma,
so the above will become excludesall=0x2C.
type Test struct {
Field `validate:"excludesall=,"` // BAD! Do not include a comma.
Field `validate:"excludesall=0x2C"` // GOOD! Use the UTF-8 hex representation.
}
Pipe ("|") is the 'or' validation tags deparator. If you wish to
have a pipe included within the parameter i.e. excludesall=| you will need to
use the UTF-8 hex representation 0x7C, which is replaced in the code as a pipe,
so the above will become excludesall=0x7C
type Test struct {
Field `validate:"excludesall=|"` // BAD! Do not include a a pipe!
Field `validate:"excludesall=0x7C"` // GOOD! Use the UTF-8 hex representation.
}
Baked In Validators and Tags
Here is a list of the current built in validators:
Skip Field
Tells the validation to skip this struct field; this is particularly
handy in ignoring embedded structs from being validated. (Usage: -)
Usage: -
Or Operator
This is the 'or' operator allowing multiple validators to be used and
accepted. (Usage: rbg|rgba) <-- this would allow either rgb or rgba
colors to be accepted. This can also be combined with 'and' for example
( Usage: omitempty,rgb|rgba)
Usage: |
StructOnly
When a field that is a nested struct is encountered, and contains this flag
any validation on the nested struct will be run, but none of the nested
struct fields will be validated. This is useful if inside of you program
you know the struct will be valid, but need to verify it has been assigned.
NOTE: only "required" and "omitempty" can be used on a struct itself.
Usage: structonly
NoStructLevel
Same as structonly tag except that any struct level validations will not run.
Usage: nostructlevel
Omit Empty
Allows conditional validation, for example if a field is not set with
a value (Determined by the "required" validator) then other validation
such as min or max won't run, but if a value is set validation will run.
Usage: omitempty
Dive
This tells the validator to dive into a slice, array or map and validate that
level of the slice, array or map with the validation tags that follow.
Multidimensional nesting is also supported, each level you wish to dive will
require another dive tag. dive has some sub-tags, 'keys' & 'endkeys', please see
the Keys & EndKeys section just below.
Usage: dive
Example #1
[][]string with validation tag "gt=0,dive,len=1,dive,required"
// gt=0 will be applied to []
// len=1 will be applied to []string
// required will be applied to string
Example #2
[][]string with validation tag "gt=0,dive,dive,required"
// gt=0 will be applied to []
// []string will be spared validation
// required will be applied to string
Keys & EndKeys
These are to be used together directly after the dive tag and tells the validator
that anything between 'keys' and 'endkeys' applies to the keys of a map and not the
values; think of it like the 'dive' tag, but for map keys instead of values.
Multidimensional nesting is also supported, each level you wish to validate will
require another 'keys' and 'endkeys' tag. These tags are only valid for maps.
Usage: dive,keys,othertagvalidation(s),endkeys,valuevalidationtags
Example #1
map[string]string with validation tag "gt=0,dive,keys,eg=1|eq=2,endkeys,required"
// gt=0 will be applied to the map itself
// eg=1|eq=2 will be applied to the map keys
// required will be applied to map values
Example #2
map[[2]string]string with validation tag "gt=0,dive,keys,dive,eq=1|eq=2,endkeys,required"
// gt=0 will be applied to the map itself
// eg=1|eq=2 will be applied to each array element in the the map keys
// required will be applied to map values
Required
This validates that the value is not the data types default zero value.
For numbers ensures value is not zero. For strings ensures value is
not "". For slices, maps, pointers, interfaces, channels and functions
ensures the value is not nil.
Usage: required
Is Default
This validates that the value is the default value and is almost the
opposite of required.
Usage: isdefault
Length
For numbers, length will ensure that the value is
equal to the parameter given. For strings, it checks that
the string length is exactly that number of characters. For slices,
arrays, and maps, validates the number of items.
Usage: len=10
Maximum
For numbers, max will ensure that the value is
less than or equal to the parameter given. For strings, it checks
that the string length is at most that number of characters. For
slices, arrays, and maps, validates the number of items.
Usage: max=10
Minimum
For numbers, min will ensure that the value is
greater or equal to the parameter given. For strings, it checks that
the string length is at least that number of characters. For slices,
arrays, and maps, validates the number of items.
Usage: min=10
Equals
For strings & numbers, eq will ensure that the value is
equal to the parameter given. For slices, arrays, and maps,
validates the number of items.
Usage: eq=10
Not Equal
For strings & numbers, ne will ensure that the value is not
equal to the parameter given. For slices, arrays, and maps,
validates the number of items.
Usage: ne=10
One Of
For strings, ints, and uints, oneof will ensure that the value
is one of the values in the parameter. The parameter should be
a list of values separated by whitespace. Values may be
strings or numbers.
Usage: oneof=red green
oneof=5 7 9
Greater Than
For numbers, this will ensure that the value is greater than the
parameter given. For strings, it checks that the string length
is greater than that number of characters. For slices, arrays
and maps it validates the number of items.
Example #1
Usage: gt=10
Example #2 (time.Time)
For time.Time ensures the time value is greater than time.Now.UTC().
Usage: gt
Greater Than or Equal
Same as 'min' above. Kept both to make terminology with 'len' easier.
Example #1
Usage: gte=10
Example #2 (time.Time)
For time.Time ensures the time value is greater than or equal to time.Now.UTC().
Usage: gte
Less Than
For numbers, this will ensure that the value is less than the parameter given.
For strings, it checks that the string length is less than that number of
characters. For slices, arrays, and maps it validates the number of items.
Example #1
Usage: lt=10
Example #2 (time.Time)
For time.Time ensures the time value is less than time.Now.UTC().
Usage: lt
Less Than or Equal
Same as 'max' above. Kept both to make terminology with 'len' easier.
Example #1
Usage: lte=10
Example #2 (time.Time)
For time.Time ensures the time value is less than or equal to time.Now.UTC().
Usage: lte
Field Equals Another Field
This will validate the field value against another fields value either within
a struct or passed in field.
Example #1:
// Validation on Password field using:
Usage: eqfield=ConfirmPassword
Example #2:
// Validating by field:
validate.VarWithValue(password, confirmpassword, "eqfield")
Field Equals Another Field (relative)
This does the same as eqfield except that it validates the field provided relative
to the top level struct.
Usage: eqcsfield=InnerStructField.Field)
Field Does Not Equal Another Field
This will validate the field value against another fields value either within
a struct or passed in field.
Examples:
// Confirm two colors are not the same:
//
// Validation on Color field:
Usage: nefield=Color2
// Validating by field:
validate.VarWithValue(color1, color2, "nefield")
Field Does Not Equal Another Field (relative)
This does the same as nefield except that it validates the field provided
relative to the top level struct.
Usage: necsfield=InnerStructField.Field
Field Greater Than Another Field
Only valid for Numbers and time.Time types, this will validate the field value
against another fields value either within a struct or passed in field.
usage examples are for validation of a Start and End date:
Example #1:
// Validation on End field using:
validate.Struct Usage(gtfield=Start)
Example #2:
// Validating by field:
validate.VarWithValue(start, end, "gtfield")
Field Greater Than Another Relative Field
This does the same as gtfield except that it validates the field provided
relative to the top level struct.
Usage: gtcsfield=InnerStructField.Field
Field Greater Than or Equal To Another Field
Only valid for Numbers and time.Time types, this will validate the field value
against another fields value either within a struct or passed in field.
usage examples are for validation of a Start and End date:
Example #1:
// Validation on End field using:
validate.Struct Usage(gtefield=Start)
Example #2:
// Validating by field:
validate.VarWithValue(start, end, "gtefield")
Field Greater Than or Equal To Another Relative Field
This does the same as gtefield except that it validates the field provided relative
to the top level struct.
Usage: gtecsfield=InnerStructField.Field
Less Than Another Field
Only valid for Numbers and time.Time types, this will validate the field value
against another fields value either within a struct or passed in field.
usage examples are for validation of a Start and End date:
Example #1:
// Validation on End field using:
validate.Struct Usage(ltfield=Start)
Example #2:
// Validating by field:
validate.VarWithValue(start, end, "ltfield")
Less Than Another Relative Field
This does the same as ltfield except that it validates the field provided relative
to the top level struct.
Usage: ltcsfield=InnerStructField.Field
Less Than or Equal To Another Field
Only valid for Numbers and time.Time types, this will validate the field value
against another fields value either within a struct or passed in field.
usage examples are for validation of a Start and End date:
Example #1:
// Validation on End field using:
validate.Struct Usage(ltefield=Start)
Example #2:
// Validating by field:
validate.VarWithValue(start, end, "ltefield")
Less Than or Equal To Another Relative Field
This does the same as ltefield except that it validates the field provided relative
to the top level struct.
Usage: ltecsfield=InnerStructField.Field
Unique
For arrays & slices, unique will ensure that there are no duplicates.
For maps, unique will ensure that there are no duplicate values.
Usage: unique
Alpha Only
This validates that a string value contains ASCII alpha characters only
Usage: alpha
Alphanumeric
This validates that a string value contains ASCII alphanumeric characters only
Usage: alphanum
Alpha Unicode
This validates that a string value contains unicode alpha characters only
Usage: alphaunicode
Alphanumeric Unicode
This validates that a string value contains unicode alphanumeric characters only
Usage: alphanumunicode
Numeric
This validates that a string value contains a basic numeric value.
basic excludes exponents etc...
for integers or float it returns true.
Usage: numeric
Hexadecimal String
This validates that a string value contains a valid hexadecimal.
Usage: hexadecimal
Hexcolor String
This validates that a string value contains a valid hex color including
hashtag (#)
Usage: hexcolor
RGB String
This validates that a string value contains a valid rgb color
Usage: rgb
RGBA String
This validates that a string value contains a valid rgba color
Usage: rgba
HSL String
This validates that a string value contains a valid hsl color
Usage: hsl
HSLA String
This validates that a string value contains a valid hsla color
Usage: hsla
E-mail String
This validates that a string value contains a valid email
This may not conform to all possibilities of any rfc standard, but neither
does any email provider accept all posibilities.
Usage: email
File path
This validates that a string value contains a valid file path and that
the file exists on the machine.
This is done using os.Stat, which is a platform independent function.
Usage: file
URL String
This validates that a string value contains a valid url
This will accept any url the golang request uri accepts but must contain
a schema for example http:// or rtmp://
Usage: url
URI String
This validates that a string value contains a valid uri
This will accept any uri the golang request uri accepts
Usage: uri
Base64 String
This validates that a string value contains a valid base64 value.
Although an empty string is valid base64 this will report an empty string
as an error, if you wish to accept an empty string as valid you can use
this with the omitempty tag.
Usage: base64
Base64URL String
This validates that a string value contains a valid base64 URL safe value
according the the RFC4648 spec.
Although an empty string is a valid base64 URL safe value, this will report
an empty string as an error, if you wish to accept an empty string as valid
you can use this with the omitempty tag.
Usage: base64url
Bitcoin Address
This validates that a string value contains a valid bitcoin address.
The format of the string is checked to ensure it matches one of the three formats
P2PKH, P2SH and performs checksum validation.
Usage: btc_addr
Bitcoin Bech32 Address (segwit)
This validates that a string value contains a valid bitcoin Bech32 address as defined
by bip-0173 (https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki)
Special thanks to Pieter Wuille for providng reference implementations.
Usage: btc_addr_bech32
Ethereum Address
This validates that a string value contains a valid ethereum address.
The format of the string is checked to ensure it matches the standard Ethereum address format
Full validation is blocked by https://github.com/golang/crypto/pull/28
Usage: eth_addr
Contains
This validates that a string value contains the substring value.
Usage: contains=@
Contains Any
This validates that a string value contains any Unicode code points
in the substring value.
Usage: containsany=!@#?
Contains Rune
This validates that a string value contains the supplied rune value.
Usage: containsrune=@
Excludes
This validates that a string value does not contain the substring value.
Usage: excludes=@
Excludes All
This validates that a string value does not contain any Unicode code
points in the substring value.
Usage: excludesall=!@#?
Excludes Rune
This validates that a string value does not contain the supplied rune value.
Usage: excludesrune=@
International Standard Book Number
This validates that a string value contains a valid isbn10 or isbn13 value.
Usage: isbn
International Standard Book Number 10
This validates that a string value contains a valid isbn10 value.
Usage: isbn10
International Standard Book Number 13
This validates that a string value contains a valid isbn13 value.
Usage: isbn13
Universally Unique Identifier UUID
This validates that a string value contains a valid UUID.
Usage: uuid
Universally Unique Identifier UUID v3
This validates that a string value contains a valid version 3 UUID.
Usage: uuid3
Universally Unique Identifier UUID v4
This validates that a string value contains a valid version 4 UUID.
Usage: uuid4
Universally Unique Identifier UUID v5
This validates that a string value contains a valid version 5 UUID.
Usage: uuid5
ASCII
This validates that a string value contains only ASCII characters.
NOTE: if the string is blank, this validates as true.
Usage: ascii
Printable ASCII
This validates that a string value contains only printable ASCII characters.
NOTE: if the string is blank, this validates as true.
Usage: printascii
Multi-Byte Characters
This validates that a string value contains one or more multibyte characters.
NOTE: if the string is blank, this validates as true.
Usage: multibyte
Data URL
This validates that a string value contains a valid DataURI.
NOTE: this will also validate that the data portion is valid base64
Usage: datauri
Latitude
This validates that a string value contains a valid latitude.
Usage: latitude
Longitude
This validates that a string value contains a valid longitude.
Usage: longitude
Social Security Number SSN
This validates that a string value contains a valid U.S. Social Security Number.
Usage: ssn
Internet Protocol Address IP
This validates that a string value contains a valid IP Address.
Usage: ip
Internet Protocol Address IPv4
This validates that a string value contains a valid v4 IP Address.
Usage: ipv4
Internet Protocol Address IPv6
This validates that a string value contains a valid v6 IP Address.
Usage: ipv6
Classless Inter-Domain Routing CIDR
This validates that a string value contains a valid CIDR Address.
Usage: cidr
Classless Inter-Domain Routing CIDRv4
This validates that a string value contains a valid v4 CIDR Address.
Usage: cidrv4
Classless Inter-Domain Routing CIDRv6
This validates that a string value contains a valid v6 CIDR Address.
Usage: cidrv6
Transmission Control Protocol Address TCP
This validates that a string value contains a valid resolvable TCP Address.
Usage: tcp_addr
Transmission Control Protocol Address TCPv4
This validates that a string value contains a valid resolvable v4 TCP Address.
Usage: tcp4_addr
Transmission Control Protocol Address TCPv6
This validates that a string value contains a valid resolvable v6 TCP Address.
Usage: tcp6_addr
User Datagram Protocol Address UDP
This validates that a string value contains a valid resolvable UDP Address.
Usage: udp_addr
User Datagram Protocol Address UDPv4
This validates that a string value contains a valid resolvable v4 UDP Address.
Usage: udp4_addr
User Datagram Protocol Address UDPv6
This validates that a string value contains a valid resolvable v6 UDP Address.
Usage: udp6_addr
Internet Protocol Address IP
This validates that a string value contains a valid resolvable IP Address.
Usage: ip_addr
Internet Protocol Address IPv4
This validates that a string value contains a valid resolvable v4 IP Address.
Usage: ip4_addr
Internet Protocol Address IPv6
This validates that a string value contains a valid resolvable v6 IP Address.
Usage: ip6_addr
Unix domain socket end point Address
This validates that a string value contains a valid Unix Address.
Usage: unix_addr
Media Access Control Address MAC
This validates that a string value contains a valid MAC Address.
Usage: mac
Note: See Go's ParseMAC for accepted formats and types:
http://golang.org/src/net/mac.go?s=866:918#L29
Hostname RFC 952
This validates that a string value is a valid Hostname according to RFC 952 https://tools.ietf.org/html/rfc952
Usage: hostname
Hostname RFC 1123
This validates that a string value is a valid Hostname according to RFC 1123 https://tools.ietf.org/html/rfc1123
Usage: hostname_rfc1123 or if you want to continue to use 'hostname' in your tags, create an alias.
Full Qualified Domain Name (FQDN)
This validates that a string value contains a valid FQDN.
Usage: fqdn
Alias Validators and Tags
NOTE: When returning an error, the tag returned in "FieldError" will be
the alias tag unless the dive tag is part of the alias. Everything after the
dive tag is not reported as the alias tag. Also, the "ActualTag" in the before
case will be the actual tag within the alias that failed.
Here is a list of the current built in alias tags:
"iscolor"
alias is "hexcolor|rgb|rgba|hsl|hsla" (Usage: iscolor)
Validator notes:
regex
a regex validator won't be added because commas and = signs can be part
of a regex which conflict with the validation definitions. Although
workarounds can be made, they take away from using pure regex's.
Furthermore it's quick and dirty but the regex's become harder to
maintain and are not reusable, so it's as much a programming philosophy
as anything.
In place of this new validator functions should be created; a regex can
be used within the validator function and even be precompiled for better
efficiency within regexes.go.
And the best reason, you can submit a pull request and we can keep on
adding to the validation library of this package!
Panics
This package panics when bad input is provided, this is by design, bad code like
that should not make it to production.
type Test struct {
TestField string `validate:"nonexistantfunction=1"`
}
t := &Test{
TestField: "Test"
}
validate.Struct(t) // this will panic
*/
package validator