feature: typed arguments

arguments.go

@@ -253,6 +253,23 @@ func NewArgument(validate ValidateOnScopeFunc) ValidatorArgument {
 	return ValidatorArgument{validate: validate}
 }
 
+// NewTypedArgument creates a generic validation argument that can help implement the validation
+// argument for client-side types.
+func NewTypedArgument[T any](v T, constraints ...Constraint[T]) ValidatorArgument {
+	return NewArgument(func(scope Scope) (*ViolationList, error) {
+		violations := NewViolationList()
+
+		for _, constraint := range constraints {
+			err := violations.AppendFromError(constraint.Validate(v, scope))
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		return violations, nil
+	})
+}
+
 // ValidatorArgument is common implementation of Argument that is used to run validation
 // process on given argument.
 type ValidatorArgument struct {

contraint.go

@@ -14,6 +14,11 @@ type Numeric interface {
 		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64
 }
 
+// Constraint is a generic interface for client-side typed constraints.
+type Constraint[T any] interface {
+	Validate(v T, scope Scope) error
+}
+
 // NilConstraint is used for a special cases to check a value for nil.
 type NilConstraint interface {
 	ValidateNil(isNil bool, scope Scope) error

example_custom_argument_constraint_test.go

@@ -28,34 +28,18 @@ func (repository *BrandRepository) FindByName(ctx context.Context, name string)
 	return found, nil
 }
 
-// You can declare you own constraint interface to create custom constraints.
-type BrandConstraint interface {
-	ValidateBrand(brand *Brand, scope validation.Scope) error
-}
-
 // To create your own functional argument for validation simply create a function with
-// a typed value and use the validation.NewArgument constructor.
-func ValidBrand(brand *Brand, constraints ...BrandConstraint) validation.ValidatorArgument {
-	return validation.NewArgument(func(scope validation.Scope) (*validation.ViolationList, error) {
-		violations := validation.NewViolationList()
-
-		for i := range constraints {
-			err := violations.AppendFromError(constraints[i].ValidateBrand(brand, scope))
-			if err != nil {
-				return nil, err
-			}
-		}
-
-		return violations, nil
-	})
+// a typed value and use the validation.NewTypedArgument constructor.
+func ValidBrand(brand *Brand, constraints ...validation.Constraint[*Brand]) validation.ValidatorArgument {
+	return validation.NewTypedArgument[*Brand](brand, constraints...)
 }
 
 // UniqueBrandConstraint implements BrandConstraint.
 type UniqueBrandConstraint struct {
 	brands *BrandRepository
 }
 
-func (c *UniqueBrandConstraint) ValidateBrand(brand *Brand, scope validation.Scope) error {
+func (c *UniqueBrandConstraint) Validate(brand *Brand, scope validation.Scope) error {
 	// usually, you should ignore empty values
 	// to check for an empty value you should use it.NotBlankConstraint
 	if brand == nil {
@@ -81,7 +65,7 @@ func (c *UniqueBrandConstraint) ValidateBrand(brand *Brand, scope validation.Sco
 		Create()
 }
 
-func ExampleNewArgument_customArgumentConstraintValidator() {
+func ExampleNewTypedArgument_customArgumentConstraintValidator() {
 	repository := &BrandRepository{brands: []Brand{{"Apple"}, {"Orange"}}}
 	isEntityUnique := &UniqueBrandConstraint{brands: repository}