Correlation, composition, aggregation, dependency ratio

The relationships between classes

1. Type:Generalization (Generalization),Dependency (Dependent Relationships),Association (Association Relationship),Aggregation (Aggregation Relationships),Composition (Synthetic Relationships).

2.   amongAggregation (Aggregation Relationships),Composition (Synthetic Relationships)belong toAssociation (Association Relationship), is a specialAssociationThe Association relationship.

3. generalization ( generalization ) is represented as an inheritance or implementation relationship (is a). The detailed form is the inheritance relationship between the class and the class, the inheritance relationship between the interface and the interface, and the implementation relationship of the class to the interface.

4.   AssociationAssociation relationships behave as variables(has a). A join between a class and a class that enables a class to know about the properties and methods of a class. Suppose, for example ,Arelies onB, youBembodied asAGlobal variables. Association relationships have two-way associations and one-way associations. Bidirectional correlation: Two classes know that there is also a class of public properties and operations. One-Way Association: There is only one class that knows the public properties and operations of a second class. Most associations should be unidirectional, and one-way relationships easier to build and maintain, helping to find classes that can be taken.

5.   Aggregation (Aggregation Relationships) is a kind of association relation, is a strong association relation. The aggregation relationship is the relationship between the whole and the individual. The two classes of the common relational relationship are at the same level, while the two classes of the aggregation relationship are at different levels, one is the whole and the other is the part. At the same time, it is a weak "owning" relationship. Reflects theAobjects can includeBobject, butBobject is notAthe component of the object. In detail, supposeAbyBPoly-Synthesis, expressed asAinclude aBthe global object, butBobject can not beACreated at the moment of creation.

6.   Composition (Combinatorial Relationships)is a kind of correlation relation, is stronger than the aggregation relationship. It requires that the object representing the whole in a common aggregation relationship be responsible for the life cycle of the object that represents the part. Composition (Combinatorial Relationships)is a strong "own" relationship, reflecting the strict part and the overall relationship, part and the overall life cycle is consistent. AssumptionsAbyBcomposition, expressed asAinclude aBthe Global object, andBobject inACreated at the moment of creation.

7.   Dependency (Dependent Relationships)represented as a parameter in a function(use a). is a connection between a class and a class, which means that a class depends on the definition of a class, and that the change of one class affects the other class. Suppose, for example ,Arelies onB, youBrepresented as a local variable, a method's argument, or a call to a static method.

8. Helios 2008-1-11

Correlation, composition, aggregation, dependency ratio