gator

Gator (or valigator) is a library that validates structs using struct tags. Here is a usage example:

// NOTE: Gator tags will only be recognized on fields that are public.
type BigStruct struct {
    Required        string  	`gator:”nonzero”`
    Email           string      `gator:”email”`
    Website         string      `gator:"url"`
    IPAddress       string      `gator:"ip"`
    PetName         string      `gator:"alpha"`
    Phone           string      `gator:"num | len(10)"`
    Password        string      `gator:”alphanum | minlen(5) | maxlen(15)"`
    DayOfWeek       int         `gator:”gte(0) | lt(7)”`
    Lat             float64     `gator:”lat”`
    Lng             float64     `gator:”lon”`
    TennisScore string          `gator:”in(love,15,30,40)”`
    NewSuperHero    string      `gator:”notin(Superman,Batman,The Flash)”`
    Zipcode         string      `gator:”match(^\d{5}(?:[-\s]\d{4})?$)”`
    Color           string      `gator:”hexcolor”`
    Ages            []int       `gator:”each( gt(18) | lt(35) )”`
}
b := &BigStruct{
	Password: "TOOOOOOOOOOOOOOO LONG",
}
if err := gator.NewStruct(b).Validate(); err != nil {
    fmt.Println(err)
}

Validation logic can be deserialized by gator using a query string:

type WebsiteListing struct {
    Url      string 
    Username string
}
website := &WebsiteListing{
    Url:      "https//news.ycombinator.com",
    Username: "hello1",
},
g := gator.NewQueryStr(website, "Url=url&Username=alphanum|minlen(5)|maxlen(10)")
if err := g.Validate(); err != nil {
    fmt.Println(err)
}

Custom tags can be added. Tokens are added statically and affect all Gators. Here is an example:

gator.RegisterStructTagToken("pword", func(s string) gator.Func {
    return gator.Matches(`^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{4,8}$`)
})
type User struct {
    Email    string `gator:”email”`
    Password string `gator:"pword"`
}
u := &User{
    Email:    "gator@example.com",
    Password: "ASDF12345",
}
if err := gator.NewStruct(u).Validate(); err != nil {
    fmt.Println(err)
}