What is builder pattern in Flutter?

Builder is a creational design pattern that lets you construct complex objects step by step. The pattern allows you to produce different types and representations of an object using the same construction code.

When Builder Is an Antipattern Unfortunately, many developers pick only part of the Builder pattern — the ability to set fields individually . The second part — presence of reasonable defaults for remaining fields — is often ignored.

A builder is a Flutter design pattern in which the construction code of a widget is defined outside of its class . Builder functions are callback interfaces that pass data (often layout-specific) to the parent widget which returns a child based on that data.