Polymorphism and Abstract Beans

Make the base class an abstract type (with subclasses); data distinguishes implementations by type name (or alias); generated code uses inheritance, and loading yields concrete subclass instances.

Good for skills, AI, quests, dungeons, and other GamePlay data where “one field, many structures”.

Schema: XML

Form 1: nested child beans (parent linked automatically)

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

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

Form 2: flat + parent

<bean name="Shape"/>
<bean name="Circle" parent="Shape" alias="圆">
  <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>

Key points:

• A parent bean with subclasses is generally an abstract type; do not write the parent name Shape as the type in data.
• Subclass fields = parent field hierarchy + own fields.
• alias lets designers write 「圆」「矩形」 in Excel.

Schema: Excel __beans__

Logically equivalent to the above (column names follow the template):

full_name	parent	alias	comment
Shape			形状基类
Circle	Shape	圆
Rect	Shape	矩形

bean	name	type
Circle	radius	float
Rect	width	float
Rect	height	float
Spawn	id	int
Spawn	shape	Shape

Nullable vs non-nullable

Field type	Meaning
Shape	Non-nullable polymorphism: every row must be some subclass; cannot fill null
Shape?	Nullable polymorphism: empty / null allowed

<var name="shape" type="Shape"/>     <!-- must fill a concrete subclass -->
<var name="shape2" type="Shape?"/>   <!-- may be null -->

In compact format, non-nullable should be {Circle,1.5}, not null. See Compact format.

How to fill data

Excel columns, compact, json, etc.: see Excel: filling polymorphism. Column sketch:

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

How to use at runtime (C# sketch)

switch (spawn.Shape)
{
    case Circle c:
        // use c.Radius
        break;
    case Rect r:
        // use r.Width / r.Height
        break;
}

With many types you can branch on GetTypeId() / __ID__ (see generated code in sample projects). Complex skill trees etc. can also put polymorphic data in JSON sources; see Other data sources.

Common pitfalls

• Forgot to define subclasses, or wrong parent spelling / module prefix.
• Wrote the abstract parent name as $type in data.
• Type is Shape (not Shape?) but filled null.
• Chinese names used by designers lack configured alias.

Related links

• Type cheat sheet
• Excel polymorphism
• XML Schema