feat: numeric-string rule added

README.md

@@ -28,7 +28,7 @@ Each validation rule in GoValidator has it's own default message, e.g: `required
 ---
 
 | Method           | Description                                                                                                         |
-|------------------|---------------------------------------------------------------------------------------------------------------------|
+| ---------------- | ------------------------------------------------------------------------------------------------------------------- |
 | RequiredInt      | `RequiredInt` checks if an integer value is provided or not.                                                        |
 | RequiredFloat    | `RequiredFloat` checks if a float value is provided or not.                                                         |
 | RequiredString   | `RequiredString` checks if a string value is empty or not.                                                          |
@@ -60,12 +60,13 @@ Each validation rule in GoValidator has it's own default message, e.g: `required
 | DefaultFloat     | `DefaultFloat` sets a default value for any pointer to a float that is passed.                                      |
 | DefaultString    | `DefaultString` sets a default value for any pointer to a string that is passed.                                    |
 | IsJSON           | `IsJSON` will check if given string is a valid JSON.                                                                |
+| NumericString    | `NumericString` will check if given value is a valid string of numbers.                                             |
 | CustomRule       | `CustomRule` is a dynamic method to define any custom validation rule.                                              |
 
 ### Functions (other common validation rules)
 ---
 | Method | Description                                                         |
-|--------|---------------------------------------------------------------------|
+| ------ | ------------------------------------------------------------------- |
 | In     | `In` checks given value is included in the provided list of values. |
 | Unique | `Unique` checks whether values in the provided slice are unique.    |
 

numeric.go

@@ -0,0 +1,32 @@
+package govalidator
+
+import "strconv"
+
+const (
+	// NumericString represents rule name which will be used to find the default error message.
+	NumericString = "numericString"
+	// NumericStringMsg is the default error message format for fields with NumericString validation rule.
+	NumericStringMsg = "%v must be a numeric string"
+
+	// bitSize is a number from 0 to 64
+	bitSize = 64
+	// base is a number from 2 to 36 or 0
+	base = 10
+)
+
+// NumericString validates that the field under validation is a numeric string.
+//
+// Example:
+//
+//	v := validator.New()
+//	v.NumericString("123456789", "postal_code", "postal_code must be a numeric string")
+//	if v.IsFailed() {
+//		 fmt.Printf("validation errors: %#v\n", v.Errors())
+//	}
+func (v Validator) NumericString(s, field, msg string) Validator {
+	_, err := strconv.ParseInt(s, base, bitSize)
+
+	v.check(err == nil, field, v.msg(NumericString, msg, field))
+
+	return v
+}

numeric_test.go

@@ -0,0 +1,62 @@
+package govalidator
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_NumericString(t *testing.T) {
+	tests := []struct {
+		name        string
+		field       string
+		value       string
+		isPassed    bool
+		msg         string
+		expectedMsg string
+	}{
+		{
+			name:        "test `1234` will pass validation as a numeric-string value",
+			field:       "postal_code",
+			value:       "1234",
+			isPassed:    true,
+			msg:         "",
+			expectedMsg: "",
+		},
+		{
+			name:        "test `abc` won't pass numeric-string validation",
+			field:       "postal_code",
+			value:       "abc",
+			isPassed:    false,
+			msg:         "",
+			expectedMsg: "postal_code must be a numeric string",
+		},
+		{
+			name:        "test ` ` won't pass numeric-string validation",
+			field:       "postal_code",
+			value:       " ",
+			isPassed:    false,
+			msg:         "postal_code must be a numeric string",
+			expectedMsg: "postal_code must be a numeric string",
+		},
+	}
+
+	for _, test := range tests {
+		v := New()
+
+		v.NumericString(test.value, test.field, test.msg)
+
+		assert.Equal(t, test.isPassed, v.IsPassed())
+
+		if !test.isPassed {
+			assert.Equalf(
+				t,
+				test.expectedMsg,
+				v.Errors()[test.field],
+				"%q failed: expected: %s, got: %s",
+				test.expectedMsg,
+				v.Errors()[test.field],
+			)
+		}
+	}
+}

validator.go

@@ -49,25 +49,26 @@ type (
 var (
 	// methodToErrorMessage contains each validation method and its corresponding error message.
 	methodToErrorMessage = map[string]string{
-		Required:  RequiredMsg,
-		Exists:    ExistsMsg,
-		Len:       LenMsg,
-		LenList:   LenListMsg,
-		Max:       MaxMsg,
-		MaxString: MaxStringMsg,
-		MinString: MinStringMsg,
-		Min:       MinMsg,
-		Between:   BetweenMsg,
-		NotExists: NotExistsMsg,
-		Regex:     RegexMsg,
-		Email:     EmailMsg,
-		UUID:      UUIDMsg,
-		Date:      DateMsg,
-		URL:       URLMsg,
-		Before:    BeforeMsg,
-		After:     AfterMsg,
-		IP4:       IP4Msg,
-		JSON:      JSONMsg,
+		Required:      RequiredMsg,
+		Exists:        ExistsMsg,
+		Len:           LenMsg,
+		LenList:       LenListMsg,
+		Max:           MaxMsg,
+		MaxString:     MaxStringMsg,
+		MinString:     MinStringMsg,
+		Min:           MinMsg,
+		Between:       BetweenMsg,
+		NotExists:     NotExistsMsg,
+		Regex:         RegexMsg,
+		Email:         EmailMsg,
+		UUID:          UUIDMsg,
+		Date:          DateMsg,
+		URL:           URLMsg,
+		Before:        BeforeMsg,
+		After:         AfterMsg,
+		IP4:           IP4Msg,
+		JSON:          JSONMsg,
+		NumericString: NumericStringMsg,
 	}
 
 	// ErrMethodMessageNotFound is the default message when a method does not have any error message on methodToErrorMessage.