Resolve your own model

Status: Current. How-to guide for developers.

This guide is for a host whose objects are neither plain classes nor dictionaries, such as an object model with metadata of its own. You give the library two views of your model: a shape for Validate and a resolver for Render.

Two interfaces describe a model. IShape is the static view Validate walks: the members a value has, whether it is a collection, the shape of its items, and the variants of an abstract shape. IResolver is the runtime view the renderer reads through: TryGetMember, Items, IsTrue, Format, Compare and Picture. The Resolver base class carries the rules this document describes for iteration, truthiness, formatting and ordering, and takes a byte array as a picture; derive from it, implement TryGetMember, and override the rest for your own value types. A resolver may hand out its own value types and recognize them again when it formats, compares or iterates them, which is how a host prints an amount in its currency.

Provider	Shape	Resolver	Members
Dictionary, in Allors.Documents	DictionaryShape.Open, new DictionaryShape(members)	DictionaryResolver	The keys of a dictionary, exactly as written, and nothing else.
Reflection, in Allors.Documents.Reflection	ReflectionShape.Of<T>(), ReflectionShape.Arguments<T>()	ReflectionResolver	Dictionary keys as written; on any other object the name with its first letter upper-cased or as written, as a property, a Get method, a get_ method, a string indexer or a field.

TryGetMember returns false for a member the scope does not have, which the renderer reports, and true with a null value for a member that is empty, which prints blank. The renderer never passes a null scope.

To put a resolver of your own in place:

1. Derive from Resolver, implement TryGetMember, and override Items, IsTrue, Format, Compare and Picture where your value types need it.
2. Implement IShape over your metadata, with Variants for an abstract shape, and build the root shape a template renders against from the same source.
3. Pass the resolver in RenderSettings.Resolver for every render, and the root shape to Validate.
4. Write a contract test that the shape and the resolver agree: every member the shape declares, the resolver reads, and a collection in the one is a collection in the other.