Change Location coordinates to pointers

Change Location.Latitude and Location.Longitude from float64 to *float64
to distinguish missing coordinates from valid (0,0) location. Add
HasCoordinates() method for safe coordinate access. Closes #5.

Author: oschwald

CHANGELOG.md

@@ -12,6 +12,13 @@
   Country) now use named types like `EnterpriseCityRecord`, `CityTraits`,
   `CountryRecord`, etc. This makes it much easier to initialize structs in user
   code while maintaining the same JSON serialization behavior.
+* **BREAKING CHANGE**: Changed `Location.Latitude` and `Location.Longitude` from
+  `float64` to `*float64` to properly distinguish between missing coordinates and
+  the valid location (0, 0). Missing coordinates are now represented as `nil`
+  and are omitted from JSON output, while valid zero coordinates are preserved.
+  This fixes the ambiguity where (0, 0) was incorrectly treated as "no data".
+  Added `Location.HasCoordinates()` method for safe coordinate access. Reported
+  by Nick Bruun. GitHub #5.
 
 # 2.0.0-beta.1 - 2025-06-22
 

README.md

@@ -82,7 +82,9 @@ func main() {
 	fmt.Printf("Russian country name: %v\n", record.Country.Names.Russian)
 	fmt.Printf("ISO country code: %v\n", record.Country.ISOCode)
 	fmt.Printf("Time zone: %v\n", record.Location.TimeZone)
-	fmt.Printf("Coordinates: %v, %v\n", record.Location.Latitude, record.Location.Longitude)
+	if record.Location.HasCoordinates() {
+		fmt.Printf("Coordinates: %v, %v\n", *record.Location.Latitude, *record.Location.Longitude)
+	}
 	// Output:
 	// Portuguese (BR) city name: Londres
 	// English subdivision name: England
@@ -161,7 +163,9 @@ func main() {
 	fmt.Printf("Country: %v (%v)\n", record.Country.Names.English, record.Country.ISOCode)
 	fmt.Printf("Continent: %v (%v)\n", record.Continent.Names.English, record.Continent.Code)
 	fmt.Printf("Postal Code: %v\n", record.Postal.Code)
-	fmt.Printf("Location: %v, %v\n", record.Location.Latitude, record.Location.Longitude)
+	if record.Location.HasCoordinates() {
+		fmt.Printf("Location: %v, %v\n", *record.Location.Latitude, *record.Location.Longitude)
+	}
 	fmt.Printf("Time Zone: %v\n", record.Location.TimeZone)
 	fmt.Printf("Network: %v\n", record.Traits.Network)
 	fmt.Printf("IP Address: %v\n", record.Traits.IPAddress)
@@ -353,7 +357,9 @@ func main() {
 	// Basic location information
 	fmt.Printf("City: %v\n", record.City.Names.English)
 	fmt.Printf("Country: %v (%v)\n", record.Country.Names.English, record.Country.ISOCode)
-	fmt.Printf("Location: %v, %v\n", record.Location.Latitude, record.Location.Longitude)
+	if record.Location.HasCoordinates() {
+		fmt.Printf("Location: %v, %v\n", *record.Location.Latitude, *record.Location.Longitude)
+	}
 
 	// Enterprise-specific fields
 	fmt.Printf("ISP: %v\n", record.Traits.ISP)

example_test.go

@@ -28,7 +28,11 @@ func Example() {
 	fmt.Printf("Russian country name: %v\n", record.Country.Names.Russian)
 	fmt.Printf("ISO country code: %v\n", record.Country.ISOCode)
 	fmt.Printf("Time zone: %v\n", record.Location.TimeZone)
-	fmt.Printf("Coordinates: %v, %v\n", record.Location.Latitude, record.Location.Longitude)
+	if record.Location.HasCoordinates() {
+		fmt.Printf("Coordinates: %v, %v\n", *record.Location.Latitude, *record.Location.Longitude)
+	} else {
+		fmt.Println("Coordinates: unavailable")
+	}
 	// Output:
 	// Portuguese (BR) city name: Londres
 	// English subdivision name: England

models.go

@@ -62,17 +62,19 @@ func (c Continent) HasData() bool {
 
 // Location contains data for the location record associated with an IP address.
 type Location struct {
-	// TimeZone is the time zone associated with location, as specified by
-	// the IANA Time Zone Database (e.g., "America/New_York")
-	TimeZone string `json:"time_zone,omitzero"       maxminddb:"time_zone"`
 	// Latitude is the approximate latitude of the location associated with
 	// the IP address. This value is not precise and should not be used to
-	// identify a particular address or household.
-	Latitude float64 `json:"latitude"                 maxminddb:"latitude"`
+	// identify a particular address or household. Will be nil if not present
+	// in the database.
+	Latitude *float64 `json:"latitude,omitzero"        maxminddb:"latitude"`
 	// Longitude is the approximate longitude of the location associated with
 	// the IP address. This value is not precise and should not be used to
-	// identify a particular address or household.
-	Longitude float64 `json:"longitude"                maxminddb:"longitude"`
+	// identify a particular address or household. Will be nil if not present
+	// in the database.
+	Longitude *float64 `json:"longitude,omitzero"       maxminddb:"longitude"`
+	// TimeZone is the time zone associated with location, as specified by
+	// the IANA Time Zone Database (e.g., "America/New_York")
+	TimeZone string `json:"time_zone,omitzero"       maxminddb:"time_zone"`
 	// MetroCode is a metro code for targeting advertisements.
 	//
 	// Deprecated: Metro codes are no longer maintained and should not be used.
@@ -89,6 +91,11 @@ func (l Location) HasData() bool {
 	return l != zeroLocation
 }
 
+// HasCoordinates returns true if both latitude and longitude are present.
+func (l Location) HasCoordinates() bool {
+	return l.Latitude != nil && l.Longitude != nil
+}
+
 // RepresentedCountry contains data for the represented country associated
 // with an IP address. The represented country is the country represented
 // by something like a military base or embassy.
@@ -342,15 +349,13 @@ type Enterprise struct {
 	// Continent contains data for the continent record associated with the IP
 	// address.
 	Continent Continent `json:"continent,omitzero"           maxminddb:"continent"`
-	// City contains data for the city record associated with the IP address.
-	City EnterpriseCityRecord `json:"city,omitzero"                maxminddb:"city"`
-	// Postal contains data for the postal record associated with the IP address.
-	Postal EnterprisePostal `json:"postal,omitzero"              maxminddb:"postal"`
 	// Subdivisions contains data for the subdivisions associated with the IP
 	// address. The subdivisions array is ordered from largest to smallest. For
 	// instance, the response for Oxford in the United Kingdom would have England
 	// as the first element and Oxfordshire as the second element.
 	Subdivisions []EnterpriseSubdivision `json:"subdivisions,omitzero"        maxminddb:"subdivisions"`
+	// Postal contains data for the postal record associated with the IP address.
+	Postal EnterprisePostal `json:"postal,omitzero"              maxminddb:"postal"`
 	// RepresentedCountry contains data for the represented country associated
 	// with the IP address. The represented country is the country represented
 	// by something like a military base or embassy.
@@ -363,11 +368,13 @@ type Enterprise struct {
 	// with the IP address. This record represents the country where the ISP has
 	// registered the IP block and may differ from the user's country.
 	RegisteredCountry CountryRecord `json:"registered_country,omitzero"  maxminddb:"registered_country"`
-	// Traits contains various traits associated with the IP address
-	Traits EnterpriseTraits `json:"traits,omitzero"              maxminddb:"traits"`
+	// City contains data for the city record associated with the IP address.
+	City EnterpriseCityRecord `json:"city,omitzero"                maxminddb:"city"`
 	// Location contains data for the location record associated with the IP
 	// address
 	Location Location `json:"location,omitzero"            maxminddb:"location"`
+	// Traits contains various traits associated with the IP address
+	Traits EnterpriseTraits `json:"traits,omitzero"              maxminddb:"traits"`
 }
 
 // HasData returns true if any GeoIP data was found for the IP in the Enterprise database.

reader_test.go

@@ -79,8 +79,8 @@ func TestReader(t *testing.T) {
 	assert.Equal(t, expectedCountryNames, record.Country.Names)
 
 	assert.Equal(t, uint16(100), record.Location.AccuracyRadius)
-	assert.InEpsilon(t, 51.5142, record.Location.Latitude, 1e-10)
-	assert.InEpsilon(t, -0.0931, record.Location.Longitude, 1e-10)
+	assert.InEpsilon(t, 51.5142, *record.Location.Latitude, 1e-10)
+	assert.InEpsilon(t, -0.0931, *record.Location.Longitude, 1e-10)
 	assert.Equal(t, "Europe/London", record.Location.TimeZone)
 
 	assert.Equal(t, uint(6269131), record.Subdivisions[0].GeoNameID)