General Responsibility Assignment Software Patterns – is composed of various instructions which make the definition of classes but also of objects in the design that are oriented by different objects. GRASP has 9 different principles and models, each of which presents as a start the problems and solutions they have:
Information expert – What is the basic principle from which the responsibility for objects is determined?
-We have to assign a class responsibility that has
necessary information in order to fulfill it
In this example, the customer class carries references to all the messages that customers have. In this way, taking responsibility from the candidate to do the calculation of the total value of the various orders, comes gradually naturally. For this reason, this is one of the main principles, but also for the fact that if we do not have all the data we need, at that time we would not be able to meet the requirements and determine the responsibility.
Creator – Who creates object A?
We need to define class B in order to create object A (or e
in other words, B contains the data of A, records them, uses them closely, and with
most importantly I have the initializing data that A) has.
This model tries to help in order to be able to decide which class should be responsible for creating a new example of a certain class. In principle, creating an object as a whole is one of the most important processes, and it is important to have a principle for deciding who should have the opportunity to create a possible class example.
Controller – Who is the first object to be used beyond the UI layer which receives and
coordinates the control that a system operation performs?
– The responsibility of an object which represents: “system” e
generally represents the “root object” as well as a usage scenario from
where the operation of the system is possible.
The high-level design of our system creates dependence on the implementation of this principle. However, we always have to define the object in order to process the business transactions that we have.
Low Merger – How do we enable the impact of change? How to make it possible to
do we support low dependency but also increased reuse?
-To determine the responsibility that belongs to us so that the union (Which in this case is
Unnecessary, to remain the same Low.
The relation is basically about the mass, how one element relates to another. In this way, the higher the union is, the greater the dependence that one element has on another.
High cohesion – The way we keep objects focused, manageable,
understandable, but also as a side role to support the low link?
-We have to assign a certain responsibility, for the sole reason that cohesion
to remain high again.
The definition of cohesion is that it has the role of a measure of how tightly all the responsibilities that the element has can be related. In general, classes that have low cohesion, have within the data that are unrelated, or that have unrelated behaviors.
Indirect – The place from where responsibility should be assigned to avoid merging in order
direct between two or even more things.
– A responsibility must be assigned to an object that is intermediate, from where
mediation of services or other components is done, for the sole reason that they
not have a direct connection.
At this moment, the position of the mediator model enters the game. Another role that Indirection has is that it supports low fusion, but at the same time reduces all readability and reasoning to be used for the whole system as a whole.
Polymorphism – How are alternatives that are based on their type treated?
-At the moment when the alternatives or even the behaviors which are
based on the type of class, determine the responsibility we should have for
behavior towards the species from where the behavior also changes, using in this way
also polymorphic operations.
Polymorphism is a term that indicates the basic design principle that is object-oriented. This principle has very strong links with what is otherwise called the Strategy Model.
Clean fabrication – Which object should have more responsibility, when we need it to violate the
High Cohesion but also the Low League. But in addition to these, the solutions
which are offered by other principles and which are not considered appropriate?
-We need to define a group that is responsible for a certain class
artificial or even a suitable class that can not do the representation of
a concept that has the domain of the problem.
In some cases, it is very difficult to understand the moment where we have to place the responsibility. This is the main reason why there is a Domain Service concept in Domain-driven Design. The logic behind these services is not directly related to the entities that are separate.
Protected variations – How to design subsystems, objects, and systems in
these elements, not to be influenced by other elements?
-How to identify points that have variations or
even the instability that is predicted, must
define the responsibility we need to create an interface that is with
This principle is the most important and is indirectly related to the other principles that GRASP has. But we must always be ready for the demands that are constantly changing, as programmers that we are.
From the blog CS@worcester – Xhulja's Blogs by xmurati and used with permission of the author. All other rights reserved by the author.