issue-#18

add “structonly” tag for struct only and not field validation

doc.go

@@ -150,6 +150,13 @@ Here is a list of the current built in validators:
 		colors to be accepted. This can also be combined with 'and' for example
 		( Usage: omitempty,rgb|rgba)
 
+	structonly
+		When a field that is a nest struct in encountered and contains this flag
+		any validation on the nested struct such as "required" will be run, but
+		none of the nested struct fields will be validated. This is usefull if
+		inside of you program you know the struct will be valid, but need to
+		verify it has been assigned.
+
 	omitempty
 		Allows conitional validation, for example if a field is not set with
 		a value (Determined by the required validator) then other validation

validator.go

@@ -22,6 +22,7 @@ const (
 	orSeparator            = "|"
 	noValidationTag        = "-"
 	tagKeySeparator        = "="
+	structOnlyTag          = "structonly"
 	omitempty              = "omitempty"
 	validationFieldErrMsg  = "Field validation for \"%s\" failed on the \"%s\" tag\n"
 	validationStructErrMsg = "Struct:%s\n"
@@ -216,6 +217,10 @@ func (v *Validator) validateStructRecursive(top interface{}, s interface{}) *Str
 
 			} else {
 
+				if strings.Contains(tag, structOnlyTag) {
+					continue
+				}
+
 				if structErrors := v.validateStructRecursive(top, valueField.Interface()); structErrors != nil {
 					validationErrors.StructErrors[typeField.Name] = structErrors
 					// free up memory map no longer needed

validator_test.go

@@ -137,6 +137,35 @@ func isEqualFunc(val interface{}, field interface{}, param string) bool {
 	return val.(string) == field.(string)
 }
 
+func (ms *MySuite) TestStructOnlyValidation(c *C) {
+
+	type Inner struct {
+		Test string `validate:"len=5"`
+	}
+
+	type Outer struct {
+		InnerStruct *Inner `validate:"required,structonly"`
+	}
+
+	outer := &Outer{
+		InnerStruct: nil,
+	}
+
+	errs := myValidator.ValidateStruct(outer).Flatten()
+	c.Assert(errs, NotNil)
+
+	inner := &Inner{
+		Test: "1234",
+	}
+
+	outer = &Outer{
+		InnerStruct: inner,
+	}
+
+	errs = myValidator.ValidateStruct(outer).Flatten()
+	c.Assert(errs, IsNil)
+}
+
 func (ms *MySuite) TestGtField(c *C) {
 
 	type TimeTest struct {