A toggle is a button, lever, switch, or other mechanism that allows users to select one of two options: on or off. It is a form of binary control typically found in electronic devices and systems and computer programming. Toggle is also a verb that means to alternate between one of two settings with a single operation, or to fasten something using a toggle.
Toggles have a variety of uses in software development including A/B testing, Canary Releases, and Champagne Brunch releases. For this reason it is important that a software product support a variety of toggle configurations to ensure that the most appropriate option is selected by the user. Fortunately, there are many different ways to configure a toggle, ranging from simple but less dynamic approaches through to highly sophisticated solutions that require the developer to deploy code to re-configure the flag at runtime.
In the context of Feature Toggles, a common approach is to hardcode the toggle state into source code, either by using comments or, more commonly, by applying a preprocessor feature like #ifdef. These methods have some drawbacks, however. The most significant is that they require the developer to restart a process in order to flip a toggle and this can significantly impact the cycle time of a validation test and, ultimately, the all-important feedback loop of CI/CD.
Other methods include exposing an endpoint that supports dynamic in-memory re-configuration of a toggle. This method is very popular with teams because it enables them to change the state of a toggle without the need for a complete re-deployment of the artifact. This, in turn, makes it much easier to validate and deploy changes to the system without impacting the user experience or slowing down the deployment process.
A final option is to rely on visual cues to communicate the state of a toggle. In some cases this is the only option available, especially if the software product does not have any other means of communicating the state of a toggle. In these cases, it is recommended that the designers of a software product use color to accentuate the active or inactive state of a toggle. For example, it is suggested that designers use a darker color to represent the active state and a lighter color to represent the inactive state. A recent study found that this technique improves perceived performance compared to using only a text label or no visual cue at all. The results of this study were consistent with previous research that suggests that a contrasting color improves the clarity and usability of a toggle switch.
