What is Fallback Value?

What is a Fallback Value?

A fallback value refers to a default or alternative value assigned to a variable, property, or function when the originally intended value is unavailable or cannot be determined. It acts as a contingency plan, ensuring that the system or application behaves predictably even in cases where the expected data or input is missing or invalid.

Usage:

Fallback values are commonly used in programming, web development, and various software applications to handle exceptional cases gracefully. They provide a way to maintain functionality and prevent unexpected errors or crashes by substituting missing or erroneous values with predetermined alternatives.

Example: web form

Consider a web form where users are required to provide their age. If the user fails to enter their age or inputs an invalid value, a fallback value can be employed to ensure the application continues to function correctly. For instance, if the user's age is missing, a fallback value such as "N/A" (Not Available) can be displayed instead.

Example: feature flag

Consider a feature flag, which should return one of several expected values.  A well-designed feature flag SDK will return a consistent fallback value (rather than null) if something goes wrong in the evaluation.  For example, all Split feature flag SDKs return “control” as the treatment name if the SDK is unable to resolve a flag name in the current context. While you could have an else if statement looking for ‘control’ it’s possible to safely code a fallback as seen below.  The important take-away here is that the safe “fallback” action should be coded into that last else statement, which acts as a catch-all for any result other than the three expected results:

Benefits:

• Enhanced Robustness: Fallback values help prevent unexpected errors or crashes by providing a reliable alternative when expected data is not available.
• Improved User Experience: By gracefully handling missing or invalid data, fallback values contribute to a smoother and more user-friendly experience.
• Maintained Functionality: Applications employing fallback values can continue to function effectively even in exceptional circumstances, ensuring uninterrupted operation.

Considerations:

• Appropriate Selection: Fallback values should be chosen carefully to ensure they accurately represent missing or invalid data without misleading users.
• Consistency: It's essential to maintain consistency in the use of fallback values across an application or system to avoid confusion.
• Testing: Thorough testing is necessary to identify potential scenarios where fallback values may be triggered and to ensure they function as intended.

In summary, fallback values play a crucial role in maintaining the reliability and usability of software systems by providing a fallback option when expected data is unavailable. By incorporating fallback values effectively, developers can enhance the robustness and user experience of their applications, contributing to overall system resilience and functionality.