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Native Components

The core elements of Arez are observables, observers and computable values and these are all that is needed at runtime for Arez to build complex applications. The first Arez applications were constructed using just these primitives.

Constructing primitives in this manner was tedious at best. Humans tend to want to use higher level abstractions and so was born the annotation driven Component Model. Arez users could define "components" that consisted of @Observable properties, @Memoize properties and @Observe methods or observers.

The component model made authoring the reactive elements of Arez applications relatively easy. However the annotation processor only used naming conventions to link primitive reactive elements together. The only way to know that two observables were from the same component was to look at their names and if enough of the prefix matched then they were probably from the same component. i.e. It is reasonably safe to assume that two observable properties named "Person.42.firstName" and "Person.42.lastName" are properties on a single component of type "Person" with id "42".

This was usually sufficient for a human who was inspecting the event logs to get a gist of the interactions between the different reactive elements but it made building a DevTool that introspected the components difficult. This lead to the creation of native components.

Native components explicitly represent the component and the observables, observers and computable values that it contains. Native components are exposed via the "spy" subsystem, allowing tools to introspect components and determine which reactive components are contained within each component. Unfortunately native components add some overhead and are only enabled if the system property "arez.enable_native_components" is true. Typically this is only enabled in development mode.

The enhanced classes generated by the annotation processor will only define native components if they are enabled. In a GWT world this is a compile-time determination and thus all code relating to native components is removed via dead code removal when "arez.enable_native_components" is false. This means that in development mode you have a runtime that allows full introspection by development tools with no overhead in production mode. The best of both worlds.