TypeTagAttribute Class Reference

Assigns a "type tag" to a synchronizer, which identifies the type of object it reads/writes within a data stream, enabling dynamic typing (polymorphic serialization and deserialization). More...

---

Source file:

• /Core/Loyc.Essentials/SyncLib/Dynamic/TypeTagAttribute.cs

Inheritance diagram for TypeTagAttribute:

Remarks

Assigns a "type tag" to a synchronizer, which identifies the type of object it reads/writes within a data stream, enabling dynamic typing (polymorphic serialization and deserialization).

Place this attribute on a synchronizer method (preferred), or on a synchronizer struct/class that implements ISyncObject{SM, T}. Do not put it on the data types being synchronized, as SyncLib does not expect business objects to be concerned with serialization.

This attribute is merely data; it is read and interpreted by TypeTagRegistry, whose virtual AttributeTagOf methods define the convention (and can be overridden to change it). In brief:

• When a synchronizer has a type tag, the tag is written whether the object appears in a statically-typed context (an explicit synchronizer was given) or a dynamically-typed one (SyncDynamicExt.SyncDynamic{SM, T}), so data written statically can be read back dynamically and vice versa.
• When reading statically, the tag in the data stream is checked against the expected tag; a mismatch is reported to TypeTagRegistry.TagMismatchError, which throws by default.
• ObjectMode.NoTypeTag suppresses the tag at a particular call site (the same mode flag must then be used when reading it back).
• TypeSyncRegistry.Add(Type, bool) records discovered tags in TypeTagRegistry.Default; an explicit tag argument in the Add<T> overloads takes precedence over this attribute.

Synchronizers without a tag behave as before: no tag is read or written unless the synchronizer calls ISyncManager.SyncTypeTag manually (a low-level technique that is incompatible with dynamic typing, because a reader must know the tag before it can choose which synchronizer to invoke).

Properties
string	Tag [get]

Public Member Functions
	TypeTagAttribute (string tag)