Overview

The following are examples of some popular use cases for imports. Fundamentally, D2 imports behave just like dependencies in other programming languages, so it is flexible for doing much more than the ones shown here.

Patterns

• Model-view
• Modular classes
• Nested composition

Principles

Alongside the patterns that imports can be used for, splitting your diagram into multiple files can also fulfill useful principles for organizations:

• Compliance. Some core piece of architecture needs to follow a spec exactly, and that file should not change while others around it can.
• Domain-driven design. Diagramming a large architecture? Get different domain experts to diagram their parts, and put them together in one diagram.
• Code reviews. While text-based diagramming makes reviewing changes possible, we've all been in situations where the diff shown makes the review appear more complex than it is. When your diagram is more modular, it's easier for everyone to know what's changed. Maybe the changes to style.d2 don't need as much scrutiny as the security.d2 file changes.
• Reusability. Your organization can define one color-classes.d2, and that can be imported and used across all diagrams for a consistent diagram style.
• Don't repeat yourself. When multiple files import an object, you only have to make changes to that one object to update it everywhere else.

More Examples

Some more creative, practical examples of using imports that mix and match the above patterns and principles.

• Version visualization
• Template