3.2.4.1 Draft sample106
Draft samples "are descriptions of co-operating objects and classes, which are custom-made, in order to solve a general draft problem in a certain context. A draft sample designates, abstracted and identifies the relevant aspects of a general draft structure " 107, helps during the component development and represents again even universal components, which can be flexibly reused. They offer simple and elegant solutions for specific problems of the object-oriented software design, by representing simple and concentrated problem solutions.
Draft samples are by the consideration developed that itself in each well structured, object-oriented architecture samples find to let must. From this less extensive and more easily understandable architectures, which already successfully converted requirements, result and concentrate the knowledge and the experiences of the programmers in such a way that always recurring problems do not have again to be solved. They consist object-oriented of objects, classes, interfaces and leaving hierarchies.
The catalog after gamma contains 23 samples in 3 different Categories 108: Production samples, structure samples and behavior patterns, which resemble each other however frequent. They contain fundamental elements how
Sample name: As a knappe designation of the problem and elucidation of the vocabulary. Problem section: As problem and description of context with conditions for the employment of a sample (motivation, purpose, basic principle, questions, application diagrams). Solution section: As abstract description of the elements, relations, competencies and interactions and arrangements of the elements of the draft as a template, here also an example code belongs to.
Consequence section: As description of the pro and cons with use, e.g. storage location consumption, run time, speaking and aspects of implementation, influence on flexibility, expandability and portability of a system, variant possibilities, traps, Tipps and techniques for the implementation, samples and well-known applications and which samples used to be together used can.
Exemplary is here the structure sample for an adapter and/or a Wrapper described109.
The sample serves the interface implementation between incompatible classes without the classes themselves be changed must. Like that a re-use of classes of a class library is possible, which otherwise not the case would be. The proceeding is to be inferred illustration 9:
The Client accesses the target category and would like to implement an operation, which does not offer the class, but one offers by the adapted class. On direct way this operation incompatibility reasons cannot out e.g. take place, therefore in this development sample a new class is inserted "adapter ", which gets both methods left by the upper classes, implements the computation and returns the result to the Client. Pro and cons of draft samples are here summarized:
| Evaluation of Draft samples110 |
| Advantages | Disadvantages |
Beside the draft sample there is among other things architecture sample, which in principle pursues the same goal of solving i.e. a specific problem by an existing template. Architecture samples are here substantially far, since they give a complete basic structure for the arrangement of elements in a software system.
- 106: See [Phil 2003] P. 42 FF
- 107: See [Gamm 1996] P. 3 FF
- 108: See [Gamm 1996] P. 8 FF
- 109: See [Gamm 1996] P. 171 FF
- 110: See [Gamm 1996] P. 4 FF and [Vran 2002] P. 1 FF