How to validate slice of string

elham anari Published at

elham anari :

I used package "gopkg.in/go-playground/validator.v9" and I read this doc . I want to validate for a slice of string.

There are some points: 1 - Variable must be slice

2 - Max len is 10

3 - Slice should not be null

4 - element slice are string

5 - Max length of every element is 12

This is code :

var validate *validator.Validate

func main() {
    validate = validator.New()
    validateVariable()
}

func validateVariable() {
mySlice := []string{"111","222"}
errs := validate.Var(mySlice , "required,max=10,min=1")
if errs != nil {
    fmt.Println(errs) 
    return
}

Aristofanio Garcia :

Package "gopkg.in/go-playground/validator.v9" is for structs and variables, look:

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.

So you can try this:

func validateVariable() {
    mySlice := []string{"111", "222"}
    //1 (to convert in error)
    println(reflect.TypeOf(mySlice).Kind() == reflect.Slice)
    //2,3,5
    errs := validate.Var(mySlice, "required,max=10,min=1,dive,max=12")
    if errs != nil {
        fmt.Println(errs)
        return
    }
    //4  (to convert in error)
    println(reflect.TypeOf(mySlice).Elem().Kind() == reflect.String)
}

With more details:

func validateVariable() {
    mySlice := []string{"111", "222"}
    //mySlice := []string{"111", "222", "", "", "", "", "", "", "", "", "", "", ""}
    //mySlice := []string{"111", "222000000000000", "0000000000000"}
    //1
    if reflect.TypeOf(mySlice).Kind() != reflect.Slice {
        fmt.Println("Invalid in: Variable must be slice")
    }
    //2
    errs2 := validate.Var(mySlice, "max=10")
    if errs2 != nil {
        fmt.Println("Invalid in: Max len is 10. Original: ")
        fmt.Println(errs2)
        return
    }
    //3
    errs3 := validate.Var(mySlice, "required")
    if errs3 != nil {
        fmt.Println("Invalid in: Slice should not be null. Original: ")
        fmt.Println(errs3)
        return
    }
    //4
    if reflect.TypeOf(mySlice).Elem().Kind() != reflect.String {
        fmt.Println("Invalid in: Element slice are string")
        return
    }
    //5
    errs5 := validate.Var(mySlice, "dive,max=12") //applied in elements
    if errs5 != nil {
        fmt.Println("Invalid in: Max length of every element is 12. Original: ")
        fmt.Println(errs5)
        return
    }
}

Another way is custom func validation. In my test I was create the functions:

//IsSlice check if field kind is equal to slice
func IsSlice(fl validator.FieldLevel) bool {
    if fl.Top().Kind() == reflect.Slice {
        return true
    }
    return false
}

//IsSlice check if field element kind is equal to string
func IsStringElem(fl validator.FieldLevel) bool {
    t := fl.Top().Type()
    if t.Elem().Kind() == reflect.String {
        return true
    }
    return false
}

Registry these functions:

func main() {
    validate = validator.New()
    validate.RegisterValidation("isslice", IsSlice)
    validate.RegisterValidation("isstringelem", IsStringElem)
    validateVariable()
}

The result is more elegant (in detail):

func validateVariable() {
    mySlice := []string{"111", "222"}
    //mySlice := []string{"111", "222", "", "", "", "", "", "", "", "", "", "", ""}
    //mySlice := []string{"111", "222000000000000", "0000000000000"}
    //1 - using tag custimized
    errs1 := validate.Var(mySlice, "isslice")
    if errs1 != nil {
        fmt.Println("Invalid in: Variable must be slice")
        fmt.Println(errs1)
        return
    }
    //2
    errs2 := validate.Var(mySlice, "max=10")
    if errs2 != nil {
        fmt.Println("Invalid in: Max len is 10. Original: ")
        fmt.Println(errs2)
        return
    }
    //3
    errs3 := validate.Var(mySlice, "required")
    if errs3 != nil {
        fmt.Println("Invalid in: Slice should not be null. Original: ")
        fmt.Println(errs3)
        return
    }
    //4 - using tag customized
    errs4 := validate.Var(mySlice, "isstringelem")
    if errs4 != nil {
        fmt.Println("Invalid in: Element slice are string")
        fmt.Println(errs4)
        return
    }
    //5
    errs5 := validate.Var(mySlice, "dive,max=12") //applied in elements
    if errs5 != nil {
        fmt.Println("Invalid in: Max length of every element is 12. Original: ")
        fmt.Println(errs5)
        return
    }
}

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