Validator: how to validate field value inside 3-rd party structure?

[gwan284]

Package version eg. v8, v9:

v9

Issue, Question or Enhancement:

I have structure that contains sql.NullFloat64 as field Latitude, for example.
I want Float64 value inside sql.NullFloat64 to be in range [-90; 90] in case of latitude.

Is there a way to enforce validation for Float64 field inside sql.NullFloat64 structure with validate tag? Or should I create custom type/validator for this?

Code sample, to showcase or reproduce:

type NullFloat64 struct {
    Float64 float64
    Valid   bool // Valid is true if Float64 is not NULL
}

type DeviceMetadata struct {
    Description  string            `json:"description" validate:"max=65535"`
    Model        string            `json:"model" validate:"max=100"`

        //how to validate Latitude.Float64 value here?
    Latitude     sql.NullFloat64 `json:"latitude" validate:"lte=90,gte=-90,omitempty"` 
    Longitude    sql.NullFloat64 `json:"longitude" validate:"lte=180,gte=-180,omitempty"`
}

[deankarn]

Hey @gwan284

You just need to register a CustomTypeFunc so that validator knows what to do about that type, there is an example of almost exactly what you want https://github.com/go-playground/validator/blob/v9/_examples/custom/main.go

Validator just uses that function so you can return the underlying value you wish to validate, in your case a float64.

Please let me know if this helps, or you have any other questions :)

[gwan284]

Thank you for response!

So CustomTypeFunc function defines how to take underlying value from type for all values of that type met.

What if I have different rules for usages of sql.NullFloat64 in another structs? Can this "ValueTaker" to be defined per object?

[deankarn]

It knows how to extract for all values you've registered the type with; unfortunately there isn't a way to specify different behaviour per object using this... however if that is needed, you can register a StructLevel validation to treat structs differently, see here for the example.

[gwan284]

Thanks for response again. Now it's absolutely clear.