How to Fill Polymorphic Data

This page covers: when a field type is an abstract bean (with multiple subclasses), how to indicate which concrete subtype a cell is.

In one sentence

Write the concrete type name (or alias) first, then fill data in that subclass’s field order.

Schema example

<bean name="Shape"/>
<bean name="Circle" parent="Shape">
  <var name="radius" type="float"/>
</bean>
<bean name="Rect" parent="Shape" alias="矩形">
  <var name="width" type="float"/>
  <var name="height" type="float"/>
</bean>

<bean name="Spawn">
  <var name="id" type="int"/>
  <var name="shape" type="Shape"/>
</bean>

Shape is the abstract base class; Circle / Rect are instantiable subclasses.

Excel: fill across columns

shape spans multiple columns: merge shape on the first row; the child row writes $type and each subclass field.

##var	id	shape
##var		$type	radius	width	height
##type	int	string	float	float	float
	1	Circle	1.5
	2	Rect		2	3
	3	矩形		4	5

Notes:

• The $type column (or the first value in the merged range) holds Circle / Rect / alias 矩形.
• Leave unrelated field columns empty.
• Without a $type column name, the convention is still “first cell in the range = type name”.

Excel: one cell (sep / lite)

When the field name or type carries sep / format, you can write it in one cell:

##var	id	shape#sep=,
##type	int	Shape
	1	Circle,1.5
	2	Rect,2,3

Or shape#format=lite:

##var	id	shape#format=lite
##type	int	Shape
	1	{Circle,1.5}
	2	{Rect,2,3}

See more in sep and Compact format.

Nullable polymorphism Shape?

Cell	Meaning
null or leave empty per rules	Empty
Circle,1.5 / {Circle,1.5}	Non-null Circle

Other data sources

Format	Type-field example
json / yaml	"shape": { "$type": "Circle", "radius": 1.5 }
lua	shape = { _type_ = "Circle", radius = 1.5 }
xml	<shape type="Circle"><radius>1.5</radius></shape>

Runtime (C# sketch)

Shape s = row.Shape;
if (s is Circle c) { /* c.Radius */ }
else if (s is Rect r) { /* r.Width, r.Height */ }

Common pitfalls

• Writing the abstract class name Shape instead of a subclass name.
• Typo in type name / alias.
• Subclass field order does not match Schema (column mode follows declaration order).
• Forgot parent in Schema, so the generated side has no polymorphism.

Related links

• Schema: Polymorphism
• Nested structures and collections
• For designers: complex structures