Original
Abstract methods
An abstract method is a virtual or
dynamic method that has no implementation in the class where it is declared.
Its implementation is deferred to a descendant class. Abstract methods must be
declared with the directive abstract after virtual or dynamic.
For example,
procedure
DoSomething; virtual; abstract;
You can call an abstract method only in a class or instance of a class in which the method has been overridden.
See also
Method declarations and implementations
译文
抽象方法
抽象方法是那些在类中声明但未实现的虚拟方法或动态方法。抽象方法的实现推延到后裔类中。声明抽象方法必需在指示字virtual或dynamic之后使用abstract。例如：
procedure
DoSomething; virtual; abstract;
只有在抽象方法已被覆盖的类或类的实例中才能对其进行调用。（也就是说，不能调用没有实现或没有定义声明的抽象方法。）