Fixing bad code in apps or incrementally adding new features once the apps are being used by consumers can be maddening for developers, but a new SDK called ROX by Rollout could help take some of the anguish out of the process.

Using ROX, which was announced by Rollout.io on April 18, developers can choose small numbers of end users to receive the fixes or new features so the apps can be tested to be sure they are working well after the changes, Erez Rusovsky, the CEO and co-founder of the company, told ITPro.

ROX by Rollout is part mobile SDK and part Software-as-a-Service (SaaS). Developers can install the SDK into their apps and then control its features within the apps through a web-based dashboard to make changes, according to Rusovsky. ROX by Rollout monitors the performance of the changes and features and then uses intelligent analytics to offer data-driven recommendations about the success of the changes and fixes and whether they are ready for full release to all other users.

Rollout calls the process "continuous feature delivery," which allows companies to improve their apps with test users to ensure improved future performance for all users, he said.

End users of the apps do not see any visual indicators of the service in their apps and no personally-identifiable information about app users is shared or used with ROX, according to Rusovsky. "Users don't know it is happening. It's like your browser being updated behind the scenes."

With ROX, "the idea is to allow developers to deploy new features to check they are not breaking anything" before releasing the apps to all users, he said. 

ROX uses feature flags, which surround a feature with a flag or notification that then gives developers control of how to deploy the change to users. A feature flag is a way of writing code which allows developers to separate features or code, he added. Rollout calls this process "continuous feature delivery."

When using ROX, developers can select users who will receive the fixes or features by country, by region or by other demographics depending on what information companies have about their customers, said Rusovsky. 

Rollout, which started its business in 2014, originally began with a hot patching application called Rollout for developers which allowed them to fix bugs in their code. ROX is an advancement of that original idea, said Rusovsky, because it not only solves the problem of fixing code but allows developers to deliver the changes in faster and safer ways.

"This covers the entire flow of releasing features," he said. "This product came from our customers of the older product [who asked for deeper capabilities] and from our understanding their needs better," he said. "We went from bug fixing to being able to turn features on and off entirely."

Once developers can see that their new changes and fixes are working as designed for their designated subsets of users, they can release the updates to all users of the affected apps. "When it's not working, we can fix it and try again," said Rusovsky. 

ROX can be used by a wide range of businesses, such as an online retail store which wants to add a new shopping cart capability to a mobile app. 

So far, ROX is available to developers of iOS apps starting at $500 per month. A free 30-day trial is also available. An Android version will be available in the future, according to the company.