From 78238071fe1ee7b725b81ed1871d64607a081908 Mon Sep 17 00:00:00 2001
From: Geoffrey Goh <kg422@cornell.edu>
Date: Thu, 12 Nov 2015 22:14:49 -0800
Subject: [PATCH] docs

---
 README.md         |  2 +-
 package-mixins.js | 17 ++++++++++-------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index a19fae5..e16df2b 100644
--- a/README.md
+++ b/README.md
@@ -265,7 +265,7 @@ The `RemotePackage` inherits all of the same properties as the `LocalPackage`, b
 - __downloadUrl__: The URL at which the package is available for download. (String). This property is only needed for advanced usage, since the `download` method will automatically handle the acquisition of updates for you.
 
 ##### Methods
-- __download(progressHandler): Promise<LocalPackage>__: Downloads the package update from the CodePush service. If a `progressHandler` is specified, it will be called periodically with an object (`{ totalBytes: Number, receivedBytes: Number }`) that reports the progress of the download till the download completes. Returns a Promise that resolves with the `LocalPackage`.
+- __download(progressHandler?: Function): Promise<LocalPackage>__: Downloads the package update from the CodePush service. If a `progressHandler` is specified, it will be called periodically with an object (`{ totalBytes: Number, receivedBytes: Number }`) that reports the progress of the download till the download completes. Returns a Promise that resolves with the `LocalPackage`.
 
 ---
 
diff --git a/package-mixins.js b/package-mixins.js
index 1bdb07b..5e8116b 100644
--- a/package-mixins.js
+++ b/package-mixins.js
@@ -11,21 +11,24 @@ module.exports = (NativeCodePush) => {
         return Promise.reject(new Error("Cannot download an update without a download url"));
       }
       
-      // Use event subscription to obtain download progress.   
-      var downloadProgressSubscription = NativeAppEventEmitter.addListener(
-        'CodePushDownloadProgress',
-        progressHandler
-      );
+      var downloadProgressSubscription;
+      if (progressHandler) {
+        // Use event subscription to obtain download progress.   
+        downloadProgressSubscription = NativeAppEventEmitter.addListener(
+          'CodePushDownloadProgress',
+          progressHandler
+        );
+      }
       
       // Use the downloaded package info. Native code will save the package info
       // so that the client knows what the current package version is.
       return NativeCodePush.downloadUpdate(this)
         .then((downloadedPackage) => {
-          downloadProgressSubscription.remove();
+          downloadProgressSubscription && downloadProgressSubscription.remove();
           return extend({}, downloadedPackage, local);
         })
         .catch((error) => {
-          downloadProgressSubscription.remove();
+          downloadProgressSubscription && downloadProgressSubscription.remove();
           // Rethrow the error for subsequent handlers down the promise chain.
           throw error;
         });