Onnew

Onnew is a naming convention used in software development to denote an event handler or callback that responds when a new item, record, or resource becomes available. It is not a language feature by itself but a pattern that appears across programming languages and frameworks in which events are exposed to user code.

In practice, a function or method named onnew is registered with an event source—such as a data stream, a collection that emits items, or a network service—that fires whenever a new entity is encountered. The handler typically receives context about the new item, allowing the program to process, validate, or store it. Handlers named onnew are common in event-driven architectures and data-processing pipelines, where timely reaction to incoming data is required.

Variations in naming reflect different language conventions. Common forms include OnNew, onNew, or onnew, depending on whether a language uses PascalCase, camelCase, or snake_case. The exact signature of an onnew handler varies, but it usually includes an argument or payload that describes the new item and may also provide metadata such as timestamps or source identifiers.

Related concepts include other event handlers such as ondata, onupdate, or ondelete, and broader design patterns like the observer pattern and publisher–subscriber models. While onnew is not a standardized API, it serves as a recognizable cue that code is designed to react to the introduction of new information or resources.