Projections

Projections are shared Chronicle read-model behavior. Use the shared docs for projection styles, model-bound projections, declarative projections, and client-tabbed examples.

• Projections
• Choosing a read model style
• Model-bound projections
• Declarative projections
• Composite keys
• TypeScript client setup

TypeScript client notes

Several projection capabilities that previously threw not implemented yet. at registration time now work end to end:

• The model-bound arithmetic decorators — @addFrom, @subtractFrom, @increment, @decrement, @count — and their fluent equivalents (.add()/.subtract()/.count() on IFromBuilder/IJoinBuilder).
• The model-bound @childrenFrom, @nested, and class- or property-level @clearWith decorators, and the matching fluent .children()/.nested() builders (plus .addChild()/.setThisValue() on IFromBuilder/IJoinBuilder).
• .usingCompositeKey()/.usingParentCompositeKey() on the fluent IFromBuilder/IJoinBuilder, for read models whose key is composed from more than one event property (see Composite keys).

If you tried any of these before and hit a not implemented yet. error, they are safe to use now.