Constructor based object initialization with overrides

• US 6,085,034 A
• Filed: 03/18/1996
• Issued: 07/04/2000
• Est. Priority Date: 03/18/1996
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Danforth, Scott Harrison
• Primary Examiner(s): Oberley, Alvin E.
• Assistant Examiner(s): STECHER, PETER S
• Application Number:
  US08/620,860
• Time in Patent Office: 1,569 Days
• Field of Search: 395/704, 395/702, 395/707, 709/300, 709/303
• US Class Current: 717/108
• CPC Class Codes: G06F 9/44552 Conflict resolution, i.e. enabling coexistence of conflicting executables
• CPC Class Codes: G06F 9/4488 Object-oriented

Abstract

An initializer which is a dynamically resolved method for initializing an object in a multiple inheritance object oriented system is introduced. The initializer is introduced in an ancestor class and can be inherited and overridden by subclasses. An overridden initializer can be invoked on an instance of a subclass to initialize an object in the system.

Claims

1. A method for initializing a first object in an object oriented class hierarchy, comprising the steps of:

defining a plurality of coexisting alternative initialization methods as dynamically resolved methods by a respective ancestor class object of a plurality of ancestor class objects of a first class object in the hierarchy;

selecting a set of ancestor class objects whose alternative initialization methods are invocable by the first class object;

dynamically selecting between the alternative initialization methods at runtime by the first class object;

overriding the selected initialization method in the selected set of ancestor class objects by the first class object; and

invoking a selected overridden initialization method on an instance of the first class object to initialize the first object.

2. The method as recited in claim 1 wherein the set of ancestor class objects are ordered in an order in which their respective initialization methods are invoked.

3. The method as recited in claim 1 wherein program logic in an overridden initialization method in the first class object which dynamically selects between alternative initialization methods in ancestor classes.

4. The method as recited in claim 3 wherein the program logic makes an explicit call to an initialization method in an ancestor class.

5. The method as recited in claim 3 wherein a control argument is used to determine whether an ancestor class should invoke a specific ancestor class during the invoking step to avoid redundant initialization of the first object.

6. The method as recited in claim 5 wherein the control argument is computed according to a dynamic runtime class ancestry.

7. A system for initializing a first object in an object oriented class hierarchy, comprising:

a memory for storing a plurality of class objects in the hierarchy;

a processor for executing methods associated with the plurality of class objects;

a plurality of coexisting alternative initialization methods defined as dynamically resolved methods in a plurality of ancestor class objects of a first class object in the hierarchy, wherein at least one ancestor class object defines more than one coexisting alternative initialization method;

an array for selecting a set of ancestor class objects whose initialization methods are invocable by the first class object;

means for dynamically selecting among the alternative initialization methods of the set of ancestor class objects at runtime by the first class object;

means for overriding the selected alternative initialization method in the first class object; and

means for invoking the selected overridden initialization method on an instance of the first class object to initialize the first object.

8. The system as recited in claim 7 wherein the set of ancestor class objects are ordered in the array in an order in which their respective initialization methods are invoked by the invoking means.

9. The method as recited in claim 7 further comprising program logic in an overridden initialization method in the first class object which dynamically selects between alternative initialization methods in ancestor classes.

10. The system as recited in claim 9 wherein the program logic further comprises an explicit call to an initialization method in an ancestor class.

11. The system as recited in claim 9 further comprising a control argument for determining whether an ancestor class should invoke a specific ancestor class.

12. The system as recited in claim 11 wherein the control argument is computed according to a dynamic runtime class ancestry.

15. The product as recited in claim 11 further comprising means for dynamically selecting between alternative initialization methods in ancestor classes.

13. A computer program product in a computer readable medium for initializing a first object in an object oriented class hierarchy, comprising:

means for defining a plurality of coexisting initialization alternatives as dynamically resolved methods by one class object in the hierarchy;

means for dynamically selecting one of the initialization alternatives at runtime by a subclass object in the hierarchy which inherits from the class object;

means for overriding at least one of the initialization methods in the subclass object in the hierarchy; and

means for invoking the overridden method to initialize the first object.

14. The product as recited in claim 13 further comprising:

means for selecting a set of ancestor class objects from all ancestor class objects whose initialization methods are invocable by the subclass object; and

means for selecting the order of the set of ancestor class objects in which their respective initialization methods are invoked.

16. The product as recited in claim 13 further comprising means for determining whether an ancestor class should invoke a specific ancestor class to avoid redundant initialization of the first object.

17. The product as recited in claim 13 further comprising means for computing a dynamic runtime class ancestry so that the determining means decision to invoke a specific ancestor class is based on runtime values.