A toggle is a control that can be used to switch between two states or options. It is commonly used in technology, computing, programming, and communications to allow users to update their preferences and settings. In the context of application design it can be used to enable or disable features, change behavior, or even alter a design.
Toggles are often used to implement responsive web designs. By allowing users to switch between different theme and layout configurations toggles can be used to provide the best user experience for any given screen size or device.
While toggles are a convenient way to implement responsiveness they can also introduce a degree of complexity to the codebase. Toggles can be difficult to debug and maintain if they are not properly managed. Savvy teams view their feature flag inventory as a carrying cost and seek to keep that number as low as possible.
The best way to do this is by being proactive in removing toggles from the production environment when they are no longer needed. This can be as simple as adding a task to the team’s backlog every time a new toggle is introduced or it may require some more advanced debugging techniques such as creating “time bombs” that will cause a test to fail if it encounters an expired toggle.
When using toggles it is important to take the time to consider if they will be accessible for users with disabilities. Toggle switches should always be clearly labeled and use standard visual design to make them distinct. In addition, designers should avoid relying on color alone to convey state. For example, a toggle switch with the color red in its on position is a cognitive problem for users who have red/green color blindness.
Another consideration is the ease with which a toggle can be re-configured. The easiest way to do this is by hardcoding the toggle configuration into the application through either a comment or an if-def in the preprocessor (where available). While these approaches are relatively easy to implement they do limit the ability of a team to re-configure the toggle through continuous deployment (CD).
A more sophisticated approach allows a developer to re-configure a toggle at runtime. This can be achieved by using a dynamic in-memory flag system which allows for the re-configuration of a toggle without restarting the application or deploying a new version. This type of approach can be very effective for Ops Toggles and other types of toggle that need to be re-configured at frequent intervals.
The best practice is to test the toggle configuration which will be live in production, and also to test a fallback configuration where all toggles are flipped Off. It is also a good idea to test any future behavior which will be enabled when a toggle is flipped On. This will help prevent surprise regressions in a future release. For more sophisticated toggles which need to be re-configured frequently this can become a significant challenge and may require an automated testing system.
