「専門演習Ⅰ」

ＵＭＬにおける実体指向

•Object-oriented concepts have been around since the 1970s. •A variety of programming languages, including C++, Smalltalk, Java, and Eiffel, implement object-oriented principles. •Object-oriented modeling languages followed close behind, built on earlier modeling environments based on basic drawing tools and procedural modeling techniques like structured analysis. •By the early 1990s formal object-oriented methods such as the Object Modeling Technique came into common use.

Object-Oriented（実体指向）

Objects and Classes （実体とクラス）

An object can be a physical entity, such as a chair or a book.

An object may also be intangible （物理的実体を伴わないもの） , such as a job or class attendance. Class attendance can be described, monitored, and reported.

Anything that you can describe can be represented as an object, and that representation can be created, manipulated, and destroyed to represent how you use the real object that it models.

What does the phrase object-oriented mean

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To use objects, we first need to distinguish between a real object and the representation of an object.

In software projects we are nearly always working with representations of objects.

The system needs to manage the representation to reflect how you are managing the real objects. 【例】 an order-processing system needs to manage 　　　　

customers, orders, and products. The software does not directly manipulate 　　　

customers, orders, or products. Instead the software creates representations called

abstractions, a general term referring to the use of objects and classes.

Creating Abstractions （抽象） of Objects （実体）

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Defining an object has to take into account information and behavior.

Each object defines three basic types of information and two types of behavior.

InformationIdentityStructureState

BehaviorWhat it can do.What can be done to it.

Defining an object

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Encapsulation is another concept that sets the object-oriented approach to software apart from its predecessors.

Encapsulation is a way to organize the many types of information and behavior described earlier so that objects can be used as efficiently and effectively as possible.

Encapsulation states that when designing an object we should separate what we know about the object according to two concepts:

2010/4/13 6２０１０年度「専門演習Ⅰ」

Encapsulation （カプセル化）

The minimum information needed to use the object.an external view that asks only,

"What can I do with this object?"

The information required to make the object work properly.an internal view that asks,

"How does this thing work?"

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Defining individual objects is just the beginning of object modeling. In order for software objects to get work done, they need to work together the way the objects they represent work together.

【例】When a customer orders tickets, the customer has to create

an order and add tickets to that order. The software objects that represent the customer, order, and

tickets need to exactly replicate the relationships between the real-world objects.

A link is a relationship between two objects. An association is a relationship between two classes. An association is the definition of a type of link in the

same way that a class is a definition of a type of object. Just as an object is an instance of a class, a link is an

instance of an association. 2010/4/13 8２０１０年度「専門演習Ⅰ」

Defining associations（関連） and links（結合）

Aggregation is a special type of association used to indicate that the participating objects are not just independent objects that know about each other.

Instead, they are assembled or configured together to create a new, more complex object. 【例】 a number of different parts can be combined

to create a physical assembly,such as a car, a boat, or a plane.

You could also create a logical assembly such as a team where the parts are not physically connected to one another but they still operate as a unit.

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Defining aggregation （集約）

Composition (構成） is used for aggregations( 集約 ) in which the life span of the part depends on the life span of the aggregate object.

The aggregate has control over the creation and destruction of the part. In short, the member object cannot exist apart from the assembly. The part object would never exist on its own, in inventory or in a parts store.

Draw this stronger form of aggregation simply by making the aggregation diamond solid (black). In Figure 4-10, the car example uses aggregation, the hollow diamond. A car contains an engine as part of its assembly.

The order example uses composition, the solid diamond. An order is composed of line items. A line item is simply a place on an order that records the fact that you want a product, along with the quantity, price, and possible discount.

Whether the order is ever placed, or the order is deleted, the product still exists. But a line item only exists as part of an order.

The line items would not continue to exist elsewhere on their own if the order was deleted.

If the order containing the line items is deleted, the line items cease to exist along with the order. 2010/4/13 10２０１０年度「専門演習Ⅰ」

Defining composition （構成）

The term generalization （汎化） is used in two ways. １．Creating a generalization is the process of organizing the features of different

types of objects that share the same purpose. A generalization is a description of the features shared by a set of objects. We

use the generalization process to create generalizations routinely to organize large amounts of information.

【例】 fruits, vegetables and meat are foods, but they are different kinds or types of

foods. Phrases like "kind of" or "type of” are often used to describe a generalization relationship between classes (for example, an apple is a type of fruit that is a kind of food and so on).

２．You might also hear this type of relationship referred to as inheritance. Many times the terms generalization and inheritance are used synonymously.

【例】 An apple is a kind of fruit, then it inherits all of the properties of fruit. Likewise,

an apple is a specialization（特化）of fruit because it inherits all of the generalized properties of fruit and adds some unique properties that make apples special or unique within the larger group of fruits.

In the reverse, we could say that the concept "fruit" is a generalization of the facts that are true for watermelons, apples, peaches, and all types of objects in the group.

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Defining inheritance （継承） / generalization （汎化）

Polymorphism is the ability to dynamically choose the method for an operation at runtime, depending on the type of object responding to the request. 【例】 < car and rocket > An application can invoke the accelerate operation

on any car, without having to first know how the individual car will implement the operation.

Polymorphism is made possible by two principles: encapsulation and generalization.

Encapsulation defines a means of organizing the information about an object so that the interface/operation is separate from the implementation/method.

Generalization defines a means of organizing class features so that shared features reside in one class and unique features reside in another class.

Applied together, these concepts say that an operation could be shared and defined in a superclass, but that the method for that operation might.be unique within each subclass.2010/4/13 12２０１０年度「専門演習Ⅰ」

Defining Polymorphism( 多態性 )

Polymorphism simply means many ways to accomplish the same thing.

A polymorphic operation has a different method in each class in which it is implemented. 【例】

Figure 4-13 models discounts. All discounts can calculate an applied discount amount. But not all discounts implement the calculation the same way. In this model, subclasses GroupDiscount, ValueDiscount, QuantityDiscount each inherit the “calculate applied discount” operation defined in the Discount class.

Each subclass provides its own method. It is also valid to provide some or all of the implementation logic in the superclass and have the subclasses inherit, and then override or extend the logic. 2010/4/13 13２０１０年度「専門演習Ⅰ」