Method, software and apparatus for referencing a method in object-based programming

• US 6,381,734 B1
• Filed: 06/03/1998
• Issued: 04/30/2002
• Est. Priority Date: 06/03/1998
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Golde, Peter H., Wiltamuth, Scott M., Wayt, Edward H., Hejlsberg, Anders, Royal, Chad W., Toutonghi, Michael J., Sharpe, Tracy C.
• Primary Examiner(s): Chaki, Kakali
• Assistant Examiner(s): Booker, Kelvin
• Application Number:
  US09/089,619
• Time in Patent Office: 1,427 Days
• Field of Search: 717/1, 717/11, 717/2, 717/10, 709/313, 709/315, 709/332, 709/310, 707/103
• US Class Current: 717/165
• CPC Class Codes: G06F 9/449 Object-oriented method invocation or resolution

Abstract

Method and apparatus for encapsulating a reference to a method in object-based programming systems and ensuring that the reference is safe are disclosed. The method of encapsulation provides for: a) defining an entity that defines the shape of the method to be referenced; b) obtaining a reference to a method; c) storing this reference in arbitrary data structures; d) passing the reference to code written by other parties; e) enabling invocation of the method by anyone holding the method reference; and f) enabling the holder of a method reference to determine the target object and method being referenced. These objectives are achieved in a strongly typed manner, making it possible for: a) developers to learn of type mismatch problems early (at compile-time) rather than late (at run-time); and b) development tools to present information to developers about the shape of components that use delegates. In addition, a model of event based programming is disclosed, wherein event-related code can be encapsulated in delegates.

Claims

1. A method for operating a computer using object-based computer code, comprising using a computer to perform the steps of

representing an instance and a first method of a class by a delegate value that can be assigned to variables and passed from one procedure to another;

and

invoking the first method by calling a second method of an instance of a class using the delegate value,

wherein the parameters supplied to the second method are supplied to the first method and the parameter list of the second method matches the parameter list of the first method, and

further wherein the first method is identified by name and by matching the parameter list and result type of the first method with the parameter list and result type declared for the class.

2. A method according to claim 1 further including the step of using program code to invoke the second method on a variable that has been assigned a value representing an instance of the class.

3. A method according to claim 1 further including the step of handling events using the first method.

4. A method according to claim 1 further including the step of invoking one or more additional first methods with the call to the second method, wherein one or more corresponding additional sets of parameters are supplied to the second method to be supplied to the one more additional first methods, respectively.

5. A method according to claim 4 further including the step of creating an invocation list associated with the second method, wherein the invocation list specifies the first methods to be invoked.

6. A method according to claim 5 further including the step of adding first methods to and deleting first methods from the invocation list.

7. An object-based computer program product comprising computer program code embodied in a computer-readable form on a physical carrier wherein the program code causes a computer to perform the steps of

representing an instance and a first method of a class by a delegate value that can be assigned to variables and passed from one procedure to another;

and

invoking the first method by calling a second method of an instance of a class using the delegate value,

wherein the parameters supplied to the second method are supplied to the first method and the parameter list of the second method matches the parameter list of the first method, and

further wherein the first method is identified by name and by matching the parameter list and result type of the first method with the parameter list and result type declared for the class.

8. A computer program product according to claim 7 further wherein program code causes the computer to invoke the second method on a variable that has been assigned a value representing an instance of the class.

9. A computer program product according to claim 7 further wherein events are handled using the first method.

10. A computer program product according to claim 7 further wherein the computer invokes one or more additional first methods with the call to the second method, wherein one or more corresponding additional sets of parameters are supplied to the second method to be supplied to the one more additional first methods, respectively.

11. A computer program product according to claim 10 further wherein there is created an invocation list associated with the second method, wherein the invocation list specifies the first methods to be invoked.

12. A computer program product according to claim 11 further wherein first methods are added to and deleted from the invocation list.

13. An object-based programming system comprising

a computer adapted to

represent an instance and a first method of a class by a delegate value that can be assigned to variables and passed from one procedure to another;

and

invoke the first method with a call to a second method of an instance of a class using the delegate value,

wherein the parameters supplied to the second method are supplied to the first method and the parameter list of the second method matches the parameter list of the first method, and

further wherein the first method is identified by name and by matching the parameter list and result type of the first method with the parameter list and result type declared for the class.

14. A programming system according to claim 13 further wherein program code causes the computer to invoke the second method on a variable that has been assigned a value representing an instance of the class.

15. A programming system according to claim 13 further wherein events are handled using the first method.

16. A programming system according to claim 13 further wherein the computer invokes one or more additional first methods with the call to the second method, wherein one or more corresponding additional sets of parameters are supplied to the second method to be supplied to the one more additional first methods, respectively.

17. A programming system according to claim 16 further wherein there is created an invocation list associated with the second method, wherein the invocation list specifies the first methods to be invoked.

18. A programming system according to claim 17 further wherein first methods are added to and deleted from the invocation list.

19. A programming system according to claim 13 further wherein the computer is adapted with software.

20. A programming system according to claim 13 further wherein the computer is adapted with hardware and software.

21. A programming system according to claim 13 further wherein the programming system includes a compiler.

22. A programming system according to claim 13 further wherein the programming system includes an interpreter.

23. A method for programming a computer in object-based computer code, comprising using a computer to perform the programming steps of:

a) defining a first class having a first method to be used to reference a second method of a second class;

b) representing an instance of the first class and the first method with a delegate value, wherein an instance of the second class and the second method are identified as parameters of the instance of the first class; and

c) invoking the second method by calling the first method on the instance of the first class using the value to reference the instance.

24. A method for operating a computer using object-based computer code, comprising using a computer to perform the steps of

representing an instance and a first static method of a class by a delegate value that can be assigned to variables and passed from one procedure to another;

and

invoking the first static method by calling a second method of an instance of a class using the delegate value,

wherein the parameters supplied to the second method are supplied to the first method and the parameter list of the second method matches the parameter list of the first method, and

further wherein the first method is identified by name and by matching the parameter list and result type of the first method with the parameter list and result type declared for the class.

25. An object-based computer program operative to cause a computer to:

1) receive the following program statements in computer readable;

a) a program statement declaring a first class to be used to invoke a method of an instance of another class, wherein the first class is declared with a parameter list and result type, and wherein the first class includes a method to be used to invoke the method of the other class;

b) a program statement instantiating an instance of the first class with the method name and the name of the instance of the other class supplied as parameters, wherein the instance and method of the first class are represented as a delegate value that can be assigned to variables and passed from one procedure to another;

c) a program statement calling the method of the instance of the first class using the delegate value and including parameters to be provided to the method of the other class; and

2) search other program statements supplied to the computer for the method of the other class and identifying it by comparing its parameter list and result type with the parameter list and result type of the first class.

26. An object-based program according to claim 25 wherein the compiler is operative on the computer to check if the method of the other class identified by the search meets one or more acceptance criteria.

27. An object-based computer program product including the following program statements encoded in computer-readable form on a physical carrier:

a) a program statement declaring a first class to be used to invoke a method of an instance of an another class, wherein the first class is declared with a parameter list and result type, and wherein the first class includes a method to be used to invoke the method of the other class;

b) a program statement instantiating an instance of the first class with the method name and instance of the other class supplied as parameters, wherein the instance and method of the first class are represented as a delegate value that can be assigned to variables and passed from one procedure to another; and

c) a program statement calling the method of the instance of the first class using the delegate value and including parameters to be provided to the method of the instance of the other class.

28. A product according to claim 27 wherein the instance of the first class is instantiated in a class having a set of security permissions, and the other class has a set of security permissions, and wherein the security permissions are encoded in computer-readable form on the carrier.

29. A computer-implemented method of calling a target method in an object-based computer program comprising

calling a first method on an instance of a first class wherein the parameters supplied to the first method include a delegate reference to the target method and instance on a second class, and wherein the first method calls the target method using the delegate reference, and

wherein the delegate reference can be assigned to variables and passed from one procedure to another, and

further wherein the instance of the first class is instantiated in a third class having a set of security permissions, the second class has a set of security permissions, and the set of security permissions of the third class are compared to the set of security permissions for the second class in order to determine if the third class can instantiate the instance of the first class.

30. A method according to claim 29 further including the step of preventing the first class from being instantiated if the call of the target method is not permitted.

31. A data structure recorded on a computer-readable medium comprising

a plurality of class definitions in an object-based computer language and a plurality of security permissions each associated with at least some of the classes,

wherein the security permissions associated with the classes are structured so that they may be compared with one another to determine if an instance of a class used to call to a method of an instance of another class may be instantiated in yet another class using a delegate value, wherein the delegate value represents a method and instance of the another class that can be assigned to variables and passed from one procedure to another.

32. A computer program product comprising a computer program encoded in computer-readable form on a physical carrier, comprising:

one or more computer program modules for reading and processing an object-based computer program to prepare it for execution; and

wherein one or more of the modules checks security permissions associated with one or more classes to determine if an instance of a class used to call to a method of an instance of another class may be instatiated in yet another class using a delegate value, wherein the delegate value represents a method and instance of the another class that can be assigned to variables and passed from one procedure to another.

33. A method of operating a computer, comprising:

reading and processing an object-based computer program to prepare it for execution; and

checking security permissions associated with one or more classes to determine if an instance of a class used to call to a method of an instance of another class may be instantiated in yet another class using a delegate value, wherein the delegate value represents a method and instance of the another class that can be assigned to variables and passed from one procedure to another.

34. A method according to claim 33 further including the step of checking that the instance of the class is a final class to facilitate a security check.

35. A computer program product comprising a computer program encoded in computer-readable form on a physical carrier, comprising:

one or more computer program modules operative on a computer for reading and processing an object-based computer program to prepare it for execution; and

wherein one or more of the modules;

1) receives the following object-based program statements in computer readable form;

a) a program statement declaring a first class to be used to invoke a method of an instance of another class, wherein the first class is declared with a parameter list and result type, and wherein the first class includes a method to be used to invoke the method of the other class;

b) a program statement instantiating an instance of the first class with the method name and the name of the instance of the other class supplied as parameters, wherein the instance and method of the first class is represented as a delegate value that can be assigned to variables and passed from one procedure to another;

c) a program statement calling the method of the instance of the first class using the delegate value and including parameters to be provided to the method of the other class; and

2) searches other program statements supplied to the computer for the method of the other class and identifying it by comparing its parameter list and result type with the parameter list and result type of the first class.

36. A computer program product comprising a computer program encoded in computer-readable form on a physical carrier, comprising:

one or more computer program modules operative on a computer for reading and processing an object-based computer program to prepare it for execution; and

wherein one or more of the modules receives in computer readable form a program statement, in an object-based computer language, declaring a class to be used to invoke a method of an instance of another class,

wherein the instance and method of the other class are represented by a delegate value that can be assigned to variables and passed from one procedure to another, and

wherein the first class is declared with a parameter list and result type, and automatically creates a method on the first class to be used to invoke the method of the instance of the other class using the delegate value.

37. An object-based program according to claim 36 wherein a module comprises functionally related computer program code and data.

38. A method comprising

a computer receiving a computer readable program statement, in an object-based computer language,

declaring a class to be used to invoke a method of an instance of another class, wherein the class is declared with a parameter list and result type, and

representing the method and instance of the another class by a delegate value that can be assigned to variables and passed from one procedure to another;

and

in response to the declaration of the class automatically creating a method on the first class to be used to invoke the method of the instance of the other class, using the delegate value.