逍遙文工作室

• NSLocationUsageDescription

在code中可要使用相對應的API：

• 使用App期間：requestWhenInUseAuthorization
• 永遠：requestAlwaysAuthorization

至於它們的作用，API是這麼解釋：

/*
 *  requestWhenInUseAuthorization
 *
 *  Discussion:
 *      When +authorizationStatus == kCLAuthorizationStatusNotDetermined,
 *      calling this method will trigger a prompt to request "when-in-use"
 *      authorization from the user.  If possible, perform this call in response
 *      to direct user request for a location-based service so that the reason
 *      for the prompt will be clear.  Any authorization change as a result of
 *      the prompt will be reflected via the usual delegate callback:
 *      -locationManager:didChangeAuthorizationStatus:.
 *
 *      If received, "when-in-use" authorization grants access to the user's
 *      location via -startUpdatingLocation/-startRangingBeaconsInRegion while
 *      in the foreground.  If updates have been started when going to the
 *      background, then a status bar banner will be displayed to maintain
 *      visibility to the user, and updates will continue until stopped
 *      normally, or the app is killed by the user.
 *
 *      "When-in-use" authorization does NOT enable monitoring API on regions,
 *      significant location changes, or visits, and -startUpdatingLocation will
 *      not succeed if invoked from the background.
 *
 *      When +authorizationStatus != kCLAuthorizationStatusNotDetermined, (ie
 *      generally after the first call) this method will do nothing.
 *
 *      If the NSLocationWhenInUseUsageDescription key is not specified in your
 *      Info.plist, this method will do nothing, as your app will be assumed not
 *      to support WhenInUse authorization.
 */
- (void)requestWhenInUseAuthorization __OSX_AVAILABLE_STARTING(__MAC_NA, __IPHONE_8_0);

/*
 *  requestAlwaysAuthorization
 *
 *  Discussion:
 *      When +authorizationStatus == kCLAuthorizationStatusNotDetermined,
 *      calling this method will trigger a prompt to request "always"
 *      authorization from the user.  If possible, perform this call in response
 *      to direct user request for a location-based service so that the reason
 *      for the prompt will be clear.  Any authorization change as a result of
 *      the prompt will be reflected via the usual delegate callback:
 *      -locationManager:didChangeAuthorizationStatus:.
 *
 *      If received, "always" authorization grants access to the user's
 *      location via any CLLocationManager API, and grants access to
 *      launch-capable monitoring API such as geofencing/region monitoring,
 *      significante location visits, etc.  Even if killed by the user, launch
 *      events triggered by monitored regions or visit patterns will cause a
 *      relaunch.
 *
 *      "Always" authorization presents a significant risk to user privacy, and
 *      as such requesting it is discouraged unless background launch behavior
 *      is genuinely required.  Do not call +requestAlwaysAuthorization unless
 *      you think users will thank you for doing so.
 *
 *      When +authorizationStatus != kCLAuthorizationStatusNotDetermined, (ie
 *      generally after the first call) this method will do nothing.
 *
 *      If the NSLocationAlwaysUsageDescription key is not specified in your
 *      Info.plist, this method will do nothing, as your app will be assumed not
 *      to support Always authorization.
 */
- (void)requestAlwaysAuthorization __OSX_AVAILABLE_STARTING(__MAC_NA, __IPHONE_8_0);

而iOS有個相當方便的API，就是可以把畫面導向系統設定(Settings)，讓使用者不再煩惱要去哪兒開啟相關設定！

if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) {
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
}

選擇的同時，會讓使用者看到我們設定目的的說明。

iOS8之後，定位服務會顯示三種狀態：永不、使用期間、永遠。

實作上，設定完info.plist後，在startUpdatingLocation前方，增加兩行code就可以在iOS 8上運作，而且iOS 8以前版本也能照舊運行！

    if ([locationManager respondsToSelector:@selector(requestWhenInUseAuthorization)]) {
        [locationManager requestWhenInUseAuthorization];
    }
    [locationManager startUpdatingLocation];

註：因為要相容iOS 8之前的版本，記得寫condition code喔！

參考：Core Location Manager Changes in iOS 8。