The metatype conflict can be avoided by manually creating the needed metaclass for C
为 C 手工创建必需的元类,可以避免元型冲突
A metatype type refers to the type of any type, including class types, structure types, enumeration types, and protocol types.
一个元类型是对任一类型(包括类类型,结构类型,枚举类型以及协议类型)的类型的引用。
Users should understand the cause and the resolution of metatype conflicts. This becomes essential when you want to use more than one custom metaclass.