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Consider the two abstract classes alpha and beta:
[<AbstractClass>]
type alpha () =
abstract member foo: beta->beta
[<AbstractClass>]
and beta () = //***
abstract member bar: alpha
If I try to compile that I get an error, on the line indicated with * * *:
error FS0010: Unexpected keyword 'and' in interaction
And if I write:
[<AbstractClass>]
type alpha () =
abstract member foo: beta->beta
and beta () =
abstract member bar: alpha
then I get:
error FS0365: No implementation was given for 'abstract member beta.bar : alpha'
and the hint that I should add the AbstractClass Attribute
So how do i declare circularly defined abstract classes?
530
You create an abstract class by declaring at least one pure virtual member function. That's a virtual function declared by using the pure specifier ( = 0 ) syntax. Classes derived from the abstract class must implement the pure virtual function or they, too, are abstract classes.
No, we can't create an object of an abstract class. But we can create a reference variable of an abstract class. The reference variable is used to refer to the objects of derived classes (subclasses of abstract class).
A method which does not have body is known as abstract method. It contains only method signature with a semi colon and, an abstract keyword before it. public abstract myMethod(); To use an abstract method, you need to inherit it by extending its class and provide implementation to it.
An abstract method in Java is declared through the keyword “abstract”.
Put the attribute after the 'and' keyword:
[<AbstractClass>]
type alpha () =
abstract member foo : beta -> beta
and [<AbstractClass>] beta () =
abstract member bar : alpha
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