Added RegisterCustomTypeFunc method and usage example.

Author: Kevin Harrington

examples/custom.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"database/sql"
+	"database/sql/driver"
+	"fmt"
+	"reflect"
+
+	validator "gopkg.in/bluesuncorp/validator.v6"
+)
+
+type DbBackedUser struct {
+	Name sql.NullString `validate:"required"`
+	Age  sql.NullInt64  `validate:"required"`
+}
+
+func main() {
+
+	config := validator.Config{
+		TagName:         "validate",
+		ValidationFuncs: validator.BakedInValidators,
+	}
+
+	validate := validator.New(config)
+
+	// register all sql.Null* types to use the ValidateValuer CustomTypeFunc
+	validate.RegisterCustomTypeFunc(ValidateValuer, sql.NullString{}, sql.NullInt64{}, sql.NullBool{}, sql.NullFloat64{})
+
+	x := DbBackedUser{Name: sql.NullString{String: "", Valid: true}, Age: sql.NullInt64{Int64: 0, Valid: false}}
+	errs := validate.Struct(x)
+
+	if len(errs) > 0 {
+		fmt.Printf("Errs:\n%+v\n", errs)
+	}
+}
+
+// ValidateValuer implements validator.CustomTypeFunc
+func ValidateValuer(field reflect.Value) interface{} {
+	if valuer, ok := field.Interface().(driver.Valuer); ok {
+		val, err := valuer.Value()
+		if err == nil {
+			return val
+		}
+		// handle the error how you want
+	}
+	return nil
+}

validator.go

@@ -157,6 +157,17 @@ func (v *Validate) RegisterValidation(key string, f Func) error {
 	return nil
 }
 
+// RegisterCustomTypeFunc registers types w/a custom type handler function.
+func (v *Validate) RegisterCustomTypeFunc(f CustomTypeFunc, sampleTypeValues ...interface{}) {
+	if v.config.CustomTypeFuncs == nil {
+		v.config.CustomTypeFuncs = map[reflect.Type]CustomTypeFunc{}
+	}
+	for _, sample := range sampleTypeValues {
+		v.config.CustomTypeFuncs[reflect.TypeOf(sample)] = f
+	}
+	v.config.hasCustomFuncs = true
+}
+
 // Field validates a single field using tag style validation and returns ValidationErrors
 // NOTE: it returns ValidationErrors instead of a single FieldError because this can also
 // validate Array, Slice and maps fields which may contain more than one error