Silences unguarded availability warnings in Auth. (#389)

Also fixes a crash in the Auth sample app in an error case.

This addresses *Auth* part of #385 .

1 files changed, 16 insertions, 1 deletions

diff --git a/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m b/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
index 8899407..8b8e1bb 100644
--- a/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
+++ b/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
@@ -40,6 +40,21 @@ static id noop(id object, SEL cmd, ...) {
 }
 #endif
 
+/** @fn isIOS9orLater
+    @brief Checks whether the iOS version is 9 or later.
+    @returns Whether the iOS version is 9 or later.
+ */
+static BOOL isIOS9orLater() {
+#if defined(__IPHONE_11_0) && (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)
+  if (@available(iOS 9.0, *)) {
+    return YES;
+  }
+  return NO;
+#else
+  return &UIApplicationOpenURLOptionsAnnotationKey;  // the constant is only available on iOS 9+
+#endif
+}
+
 @implementation FIRAuthAppDelegateProxy {
   /** @var _appDelegate
       @brief The application delegate whose method is being swizzled.
@@ -119,7 +134,7 @@ static id noop(id object, SEL cmd, ...) {
     SEL openURLOptionsSelector = @selector(application:openURL:options:);
     SEL openURLAnnotationSelector = @selector(application:openURL:sourceApplication:annotation:);
     SEL handleOpenURLSelector = @selector(application:handleOpenURL:);
-    if (&UIApplicationOpenURLOptionsAnnotationKey &&  // the constant is only available on iOS 9+
+    if (isIOS9orLater() &&
         ([_appDelegate respondsToSelector:openURLOptionsSelector] ||
          (![_appDelegate respondsToSelector:openURLAnnotationSelector] &&
           ![_appDelegate respondsToSelector:handleOpenURLSelector]))) {