Digits checker is added. (#37)

Fixes #20

README.md

@@ -67,6 +67,7 @@ type Person struct {
 This package currently provides the following checkers:
 
 - [ascii](doc/checkers/ascii.md) checks if the given string consists of only ASCII characters.
+- [digits](doc/checkers/digits.md) checks if the given string consists of only digit characters.
 - [max](doc/checkers/max.md) checks if the given value is less than the given maximum.
 - [max-length](doc/checkers/maxlength.md) checks if the length of the given value is less than the given maximum length.
 - [min](doc/checkers/min.md) checks if the given value is greather than the given minimum.

checker.go

@@ -32,6 +32,7 @@ const ResultValid Result = "VALID"
 // makers provides mapping to maker function for the checkers.
 var makers = map[string]MakeFunc{
 	CheckerAscii:     makeAscii,
+	CheckerDigits:    makeDigits,
 	CheckerMax:       makeMax,
 	CheckerMaxLength: makeMaxLength,
 	CheckerMin:       makeMin,

digits.go

@@ -0,0 +1,36 @@
+package checker
+
+import (
+	"reflect"
+)
+
+// CheckerDigits is the name of the checker.
+const CheckerDigits = "digits"
+
+// ResultNotDigits indicates that the given string contains non-digit characters.
+const ResultNotDigits = "NOT_DIGITS"
+
+// IsDigits checks if the given string consists of only digit characters.
+func IsDigits(value string) Result {
+	for i := 0; i < len(value); i++ {
+		if value[i] < '0' || value[i] > '9' {
+			return ResultNotDigits
+		}
+	}
+
+	return ResultValid
+}
+
+// makeDigits makes a checker function for the digits checker.
+func makeDigits(_ string) CheckFunc {
+	return checkDigits
+}
+
+// checkDigits checks if the given string consists of only digit characters.
+func checkDigits(value, _ reflect.Value) Result {
+	if value.Kind() != reflect.String {
+		panic("string expected")
+	}
+
+	return IsDigits(value.String())
+}

digits_test.go

@@ -0,0 +1,57 @@
+package checker
+
+import "testing"
+
+func TestIsDigitsInvalid(t *testing.T) {
+	if IsDigits("checker") == ResultValid {
+		t.Fail()
+	}
+}
+
+func TestIsDigitsValid(t *testing.T) {
+	if IsDigits("1234") != ResultValid {
+		t.Fail()
+	}
+}
+
+func TestCheckDigitsNonString(t *testing.T) {
+	defer FailIfNoPanic(t)
+
+	type User struct {
+		Id int `checkers:"digits"`
+	}
+
+	user := &User{}
+
+	Check(user)
+}
+
+func TestCheckDigitsInvalid(t *testing.T) {
+	type User struct {
+		Id string `checkers:"digits"`
+	}
+
+	user := &User{
+		Id: "checker",
+	}
+
+	_, valid := Check(user)
+	if valid {
+		t.Fail()
+	}
+}
+
+func TestCheckDigitsValid(t *testing.T) {
+	type User struct {
+		Id string `checkers:"digits"`
+	}
+
+	user := &User{
+		Id: "1234",
+	}
+
+	_, valid := Check(user)
+	if !valid {
+		t.Fail()
+	}
+}

doc/checkers/ascii.md

@@ -1,6 +1,6 @@
 # ASCII Checker
 
-The ```ascii``` checkr checks if the given string consists of only ASCII characters. If the string contains non-ASCII characters, the checker will return the ```NOT_ASCII``` result. Here is an example:
+The ```ascii``` checker checks if the given string consists of only ASCII characters. If the string contains non-ASCII characters, the checker will return the ```NOT_ASCII``` result. Here is an example:
 
 ```golang
 type User struct {

doc/checkers/digits.md

@@ -0,0 +1,28 @@
+# Digits Checker
+
+The ```digits``` checker checks if the given string consists of only digit characters. If the string contains non-digit characters, the checker will return the ```NOT_DIGITS``` result. Here is an example:
+
+```golang
+type User struct {
+  Id string `checkers:"digits"`
+}
+
+user := &User{
+  Id: "1234",
+}
+
+_, valid := Check(user)
+if !valid {
+  // Send the mistakes back to the user
+}
+```
+
+In your custom checkers, you can call the ```digits``` checker function ```IsDigits``` to validate the user input. Here is an example:
+
+```golang
+result := IsDigits("1234")
+
+if result != ResultValid {
+  // Send the mistakes back to the user
+}
+```