How can I validate an array of strings from a JSON in Golang with validator package?

Question

I'm using the package validator to help me deal with JSON fields in golang. I know how to use oneof to check for specific values in a field. Is there any option for doing the same, but for an array of strings?

I'm trying to do something like this:

type ResponseEntity struct {
    Values       []string  `json:"values" validate:"oneof=VALUE1 VALUE2 VALUE3"`
}

Answer 1

As @mkopriva points out, you can use the dive keyword to check the elements of a slice.

To offer more explanation:

• some rules, like min are overloaded and apply to both scalar and slice types
• other rules, like oneof apply only to scalars; (in the example below, a call to validate.Struct causes a panic when the struct has a oneof rule directly on a slice)
• dive pushes rules like oneof down to the elements of a slice. (the example also shows min, dive, and oneof working together without panicking).

type (
    demoA struct {
        Values []string `validate:"oneof=VALUE1 VALUE2 VALUE3"`
    }
    demoB struct {
        Values []string `validate:"min=1"`
    }
    demoC struct {
        Values []string `validate:"min=1,dive,oneof=VALUE1 VALUE2 VALUE3"`
    }
)

var validate = validator.New()

func main() {
    safeValidate(demoA{[]string{}})
    fmt.Println()

    doValidate(demoB{[]string{}})
    doValidate(demoB{[]string{"foo"}})
    fmt.Println()

    doValidate(demoC{[]string{}})
    doValidate(demoC{[]string{"foo"}})
    doValidate(demoC{[]string{"VALUE2"}})
    fmt.Println()
}