如果希望增加属性，您必须把price元素定义成复杂类型。

If you want to add an attribute, you must define price as a complex type.

youdao

和一般的类别不同，一个类的扩展可以为其增加属性和实例变量。

Unlike regular categories, a class extension can add its own properties and instance variables to a class.

youdao

和一般的类别不同，一个类的扩展可以为其增加属性和实例变量。如果你像下面这样声明属性。

Unlike regular categories, a class extension can add its own properties and instance variables to a class. If you declare a property in a class extension, like this.

youdao

Having created c p 1 and c p 2, I had this weird looking form here.

我可以在类中建立一些属性，我可以给类增加一些特征。

麻省理工公开课 - 计算机科学及编程导论课程节选