Symbiont Pattern


The active object symbiont pattern is a structural pattern that provides a means of dynamically adding output interfaces to a host active object. The

A short statement that answers the following questions:

What does this design pattern do?
What is its rationale and intent?
What particular design issue or problem does it address?

Also Known As

Other well-known names for the pattern, if any.


A scenario that illustrates a design problem and how the class and object structures in the pattern solve the problem. The scenario will help you understand the more abstract description of the pattern that follows.


What are the situations in which the design pattern can be applied? What are examples of poor designs that the pattern can address? How can you recognize these situations?


A graphical representation of the classes in the pattern using a notation based on the Object Modeling Technique. We also use interaction diagrams to illustrate sequences of requests and collaborations between objects.


The classes and/or objects participating in the design pattern and their responsibilities.


How the participants collaborate to carry out their responsibilities.


How does the pattern support its objectives? What are the trade-offs and results of using the pattern? What aspect of system structure does it let you var independently?


What pitfalls, hints, or techniques should you be aware of when implementing the pattern? Are there language-specific issues?

Sample Code

Code fragments that illustrate how you might implement the pattern in C++ or Smalltalk.

Known Uses

Examples of the pattern found in real systems. We include at least two examples from different domains.

Related Patterns

What design patterns are closely related to this one? What are the important differences? With which other patterns should this one be used?