feat: add listener.isListening

Author: codebytere

README.md

@@ -234,7 +234,7 @@ console.log(`Contact was ${updated ? 'updated' : 'not updated'}.`)
 
 This module exposes an `EventEmitter`, which can be used to listen to potential changes to the `CNContactStore`. When a contact is changed either with methods contained in this module, or manually by a user, the `contact-changed` event will be emitted.
 
-Owing to the underlying architecture of this module, the listener must be manually managed; before use you must initialize it with `listener.setup()` and when you are finished listening for events you must remove it with `listener.remove()`
+Owing to the underlying architecture of this module, the listener must be manually managed; before use you must initialize it with `listener.setup()` and when you are finished listening for events you must remove it with `listener.remove()`. To check if a listener is currently active, use `listener.isListening()`.
 
 Example Usage:
 

contacts.mm

@@ -171,36 +171,29 @@
     contact.Set("contactThumbnailImage", image_buffer);
   }
 
-  if ([cncontact isKeyAvailable:CNContactJobTitleKey]) {
+  if ([cncontact isKeyAvailable:CNContactJobTitleKey])
     contact.Set("jobTitle", std::string([[cncontact jobTitle] UTF8String]));
-  }
 
-  if ([cncontact isKeyAvailable:CNContactDepartmentNameKey]) {
+  if ([cncontact isKeyAvailable:CNContactDepartmentNameKey])
     contact.Set("departmentName",
                 std::string([[cncontact departmentName] UTF8String]));
-  }
 
-  if ([cncontact isKeyAvailable:CNContactOrganizationNameKey]) {
+  if ([cncontact isKeyAvailable:CNContactOrganizationNameKey])
     contact.Set("organizationName",
                 std::string([[cncontact organizationName] UTF8String]));
-  }
 
-  if ([cncontact isKeyAvailable:CNContactNoteKey]) {
+  if ([cncontact isKeyAvailable:CNContactNoteKey])
     contact.Set("note", std::string([[cncontact note] UTF8String]));
-  }
 
-  if ([cncontact isKeyAvailable:CNContactMiddleNameKey]) {
+  if ([cncontact isKeyAvailable:CNContactMiddleNameKey])
     contact.Set("middleName", std::string([[cncontact middleName] UTF8String]));
-  }
 
-  if ([cncontact isKeyAvailable:CNContactInstantMessageAddressesKey]) {
+  if ([cncontact isKeyAvailable:CNContactInstantMessageAddressesKey])
     contact.Set("instantMessageAddresses",
                 GetInstantMessageAddresses(env, cncontact));
-  }
 
-  if ([cncontact isKeyAvailable:CNContactSocialProfilesKey]) {
+  if ([cncontact isKeyAvailable:CNContactSocialProfilesKey])
     contact.Set("socialProfiles", GetSocialProfiles(env, cncontact));
-  }
 
   return contact;
 }
@@ -509,8 +502,16 @@ CNAuthorizationStatus AuthStatus() {
   return Napi::Boolean::New(env, success);
 }
 
+// Sets up event listening for changes to the CNContactStore.
 Napi::Boolean SetupListener(const Napi::CallbackInfo &info) {
   Napi::Env env = info.Env();
+
+  if (observer) {
+    Napi::Error::New(env, "An observer is already observing")
+        .ThrowAsJavaScriptException();
+    return Napi::Boolean::New(env, false);
+  }
+
   ts_fn = Napi::ThreadSafeFunction::New(env, info[0].As<Napi::Function>(),
                                         "emitCallback", 0, 1);
 
@@ -529,27 +530,46 @@ CNAuthorizationStatus AuthStatus() {
   return Napi::Boolean::New(env, true);
 }
 
+// Removes event listening for changes to the CNContactStore.
 Napi::Boolean RemoveListener(const Napi::CallbackInfo &info) {
   Napi::Env env = info.Env();
 
   if (!observer) {
-    Napi::Error::New(env, "No observers are currently listening")
+    Napi::Error::New(env, "No observers are currently observing")
         .ThrowAsJavaScriptException();
     return Napi::Boolean::New(env, false);
   }
 
+  // Release thread-safe function.
   ts_fn.Release();
+
+  // Remove observer from the Notification Center.
   [[NSNotificationCenter defaultCenter] removeObserver:observer];
 
+  // Reset observer.
+  observer = nullptr;
+
   return Napi::Boolean::New(env, true);
 }
 
+// Indicates whether event listening for changes to the CNContactStore is in
+// place.
+Napi::Boolean IsListening(const Napi::CallbackInfo &info) {
+  Napi::Env env = info.Env();
+
+  bool is_listening = observer != nullptr;
+
+  return Napi::Boolean::New(env, is_listening);
+}
+
 // Initializes all functions exposed to JS.
 Napi::Object Init(Napi::Env env, Napi::Object exports) {
   exports.Set(Napi::String::New(env, "setupListener"),
               Napi::Function::New(env, SetupListener));
   exports.Set(Napi::String::New(env, "removeListener"),
               Napi::Function::New(env, RemoveListener));
+  exports.Set(Napi::String::New(env, "isListening"),
+              Napi::Function::New(env, IsListening));
   exports.Set(Napi::String::New(env, "getAuthStatus"),
               Napi::Function::New(env, GetAuthStatus));
   exports.Set(Napi::String::New(env, "getAllContacts"),

index.js

@@ -12,6 +12,8 @@ listener.remove = () => {
   contacts.removeListener()
 }
 
+listener.isListening = () => contacts.isListening()
+
 const optionalProperties = [
   'jobTitle',
   'departmentName',

test/module.spec.js

@@ -203,10 +203,23 @@ describe('node-mac-contacts', () => {
   })
 
   describe('listener', () => {
+    afterEach(() => {
+      if (listener.isListening()) {
+        listener.remove()
+      }
+    })
+
     it('throws when trying to remove a nonexistent listener', () => {
       expect(() => {
         listener.remove()
-      }).to.throw(/No observers are currently listening/)
+      }).to.throw(/No observers are currently observing/)
+    })
+
+    it('throws when trying to setup an already-existent listener', () => {
+      expect(() => {
+        listener.setup()
+        listener.setup()
+      }).to.throw(/An observer already observing/)
     })
 
     it('emits an event when the contact is changed', (done) => {
@@ -222,7 +235,6 @@ describe('node-mac-contacts', () => {
       })
 
       listener.once('contact-changed', () => {
-        listener.remove()
         done()
       })
     })