Same checker is added.

README.md

@@ -67,3 +67,4 @@ type Person struct {
 This package currently provides the following checkers:
 
 - [required](docs/checkers/required.md) checks if the required value is provided.
+- [same](docs/checkers/same.md) checks if the given value is equal to the value of the field with the given name.

checker.go

@@ -32,6 +32,7 @@ const ResultValid Result = "VALID"
 // makers provides mapping to maker function for the checkers.
 var makers = map[string]MakeFunc{
 	"required": makeRequired,
+	"same":     makeSame,
 }
 
 // Register registers the given checker name and the maker function.

doc/checkers/same.md

@@ -0,0 +1,20 @@
+# Same Checker
+
+The ```same``` checker checks if the given value is equal to the value of the other field specified by its name. If they are not equal, the checker will return the ```NOT_SAME``` result. In the example below, the ```same``` checker ensures that the value in the ```Confirm``` field matches the value in the ```Password``` field.
+
+```golang
+type User struct {
+    Password string
+    Confirm  string `checkers:"same:Password"`
+}
+
+user := &User{
+    Password: "1234",
+    Confirm:  "1234",
+}
+
+mistakes, valid := checker.Check(user)
+if !valid {
+    // Send the mistakes back to the user
+}
+```

same.go

@@ -0,0 +1,32 @@
+package checker
+
+import (
+	"reflect"
+)
+
+// ResultNotSame indicates that the given two values are not equal to each other.
+const ResultNotSame = "NOT_SAME"
+
+// makeSame makes a checker function for the same checker.
+func makeSame(config string) CheckFunc {
+	return func(value, parent reflect.Value) Result {
+		return checkSame(value, parent, config)
+	}
+}
+
+// checkSame checks if the given value is equal to the value of the field with the given name.
+func checkSame(value, parent reflect.Value, name string) Result {
+	other := parent.FieldByName(name)
+
+	if !other.IsValid() {
+		panic("other field not found")
+	}
+
+	other = reflect.Indirect(other)
+
+	if !value.Equal(other) {
+		return ResultNotSame
+	}
+
+	return ResultValid
+}

same_test.go

@@ -0,0 +1,80 @@
+package checker
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestSameValid(t *testing.T) {
+	type User struct {
+		Password string
+		Confirm  string `checkers:"same:Password"`
+	}
+
+	user := &User{
+		Password: "1234",
+		Confirm:  "1234",
+	}
+
+	_, valid := Check(user)
+	if !valid {
+		t.Fail()
+	}
+}
+
+func TestSameInvalid(t *testing.T) {
+	type User struct {
+		Password string
+		Confirm  string `checkers:"same:Password"`
+	}
+
+	user := &User{
+		Password: "1234",
+		Confirm:  "12",
+	}
+
+	_, valid := Check(user)
+	if valid {
+		t.Fail()
+	}
+}
+
+func TestSameWithoutParent(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fail()
+		}
+	}()
+
+	type User struct {
+		Password string
+		Confirm  string `checkers:"same:Password"`
+	}
+
+	user := &User{
+		Password: "1234",
+		Confirm:  "12",
+	}
+
+	checkSame(reflect.ValueOf(user.Confirm), reflect.ValueOf(nil), "Password")
+}
+
+func TestSameInvalidName(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fail()
+		}
+	}()
+
+	type User struct {
+		Password string
+		Confirm  string `checkers:"same:Unknown"`
+	}
+
+	user := &User{
+		Password: "1234",
+		Confirm:  "1234",
+	}
+
+	Check(user)
+}