Add HasPostalCode method on Country type

country.go

@@ -138,10 +138,16 @@ func (c *Country) SubdivisionByName(name string) Subdivision {
 	return Subdivision{}
 }
 
+// HasPostalCode determines whether the country has postal codes. It returns
+// true if the country has postal codes, and false if it does not.
+func (c *Country) HasPostalCode() bool {
+	return c.PostalCodeFormat != ""
+}
+
 // MatchPostalCode returns true if postalCode has a valid format for the
 // country. If the country does not have a postal code, returns false.
 func (c *Country) MatchPostalCode(postalCode string) bool {
-	if c.PostalCodeFormat == "" {
+	if !c.HasPostalCode() {
 		return false
 	}
 	r := regexp.MustCompile(c.PostalCodeFormat)

country_test.go

@@ -342,6 +342,14 @@ func TestTranslations(t *testing.T) {
 	assert.Equal(t, "", c.Translations["xx"])
 }
 
+func TestHasPostalCode(t *testing.T) {
+	it := countries.Get("IT")
+	assert.True(t, it.HasPostalCode())
+
+	jm := countries.Get("JM")
+	assert.False(t, jm.HasPostalCode())
+}
+
 func TestMatchPostalCode(t *testing.T) {
 	it := countries.Get("IT")
 	assert.True(t, it.MatchPostalCode("35018"))