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In Objective-C, for example, both the generic Object and NSObject (in Cocoa/OpenStep) provide the method isMemberOfClass: which returns true if the argument to the method is an instance of the specified class. The method isKindOfClass: analogously returns true if the argument inherits from the specified class.
The method Print in class Box, by invoking the parent version of method Print, is also able to output the private variables length and width of the base class. Otherwise, these variables are inaccessible to Box. The following statements will instantiate objects of type Rectangle and Box, and call their respective Print methods:
Many languages have explicit pointers or references. Reference types differ from these in that the entities they refer to are always accessed via references; for example, whereas in C++ it's possible to have either a std:: string and a std:: string *, where the former is a mutable string and the latter is an explicit pointer to a mutable string (unless it's a null pointer), in Java it is only ...
In computer science, boxing (a.k.a. wrapping) is the transformation of placing a primitive type within an object so that the value can be used as a reference. Unboxing is the reverse transformation of extracting the primitive value from its wrapper object. Autoboxing is the term for automatically applying boxing and/or unboxing transformations ...
In some languages, for example C++, Java, and Raku this or self is a keyword, and the variable automatically exists in instance methods. In others, for example, Python, Rust, and Perl 5, the first parameter of an instance method is such a reference. It needs to be specified explicitly.
Python allows the creation of class methods and static methods via the use of the @classmethod and @staticmethod decorators. The first argument to a class method is the class object instead of the self-reference to the instance. A static method has no special first argument. Neither the instance, nor the class object is passed to a static method.
create object variable ... basic/void method value-returning method ABAP Objects ... Java — D x.property: Python Visual Basic .NET Xojo
Objects are never created implicitly but instead are always passed or assigned by a reference variable. (Methods in Java are always pass by value, however, it is the value of the reference variable that is being passed.) [11] The Java Virtual Machine manages garbage collection so that objects are cleaned up after they are no longer reachable ...