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singleton^2
subjectfact 
singleton^2has definition A class for which only one instance should exist2001-08-30 14:57:32.0
is a subtopic of 6.5 - The Singleton Pattern2001-08-30 14:57:32.0
is a kind of class2001-08-30 14:57:32.0
classcan have instances2001-08-30 14:54:50.0
contains all of the code that relates to its objects including
  • code describing how the objects of the class are structured - i.e. the data stored in each object that implement the properties
  • The procedures, called methods, that implement the behaviour of the objects
2001-08-30 14:54:50.0
contains data associated with each object2001-08-30 14:54:50.0
declares a list of variables, called instance variables, corresponding to data that will be present in each instance2001-08-30 14:54:50.0
has part class name2001-08-30 14:54:50.0
has part class variable2001-08-30 14:54:50.0
has part code2001-08-30 14:54:50.0
has part constructor2001-08-30 14:54:50.0
has part instance variable2001-08-30 14:54:50.0
has part method2001-08-30 14:54:51.0
has part variables2001-08-30 14:54:51.0
is an abstract representation of all the instances of that class that may ever exist2001-08-30 14:54:51.0
is probably useless if it has no responsibilities attached to it2001-08-30 14:54:51.0
is the unit of data abstraction in an object-oriented program2001-08-30 14:54:51.0
is divided up into methods2001-08-30 14:54:51.0
is drawn as a box with the name of the class inside in a UML class diagram2001-08-30 14:54:51.0
is needed in a domain model if you have to store or manipulate instances of it in order to implement a requirement2001-08-30 14:54:51.0
represents several similar objects2001-08-30 14:54:51.0
see also class^22001-08-30 14:54:51.0
should be created to hold a responsibility if the responsibility cannot be attributed to any of the existing classes2001-08-30 14:54:51.0
should be named after things their instances represent in the real world2001-08-30 14:54:51.0
should have a comment at the top describing the purpose of the class, how it should be used, its authors and its history of modification2001-08-30 14:54:51.0
should not be named after the internals of a computer system such as 'Record', 'Table', 'Data', 'Structure', or 'Information'2001-08-30 14:54:51.0
data abstractiongroups the pieces of data that describe some entity, so that programmers can manipulate that data as a unit2001-08-30 14:55:09.0
helps a programmer to cope with the complexity of data2001-08-30 14:55:09.0
hides the details of data2001-08-30 14:55:09.0

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