什么是0,1 ,. ,*在此Yii2文档图像中

Question

来自Yii的文件

http://www.yiiframework.com/doc-2.0/guide-start-workflow.html#application-structure

这意味着什么？

Answer 1

这些是UML图中不同类型的多重性.

Multiplicity Option Cardinality
0..0         0      Collection must be empty
0..1                No instances or one instance
1..1         1      Exactly one instance
0..*         *      Zero or more instances
1..*                At least one instance
5..5         5      Exactly 5 instances
m..n                At least m but no more than n instances

在此处查看更多信息.