Six relationships of UML class diagram, the best way to learn and understand

UML What is it? ？

The more official description is like this ：

UML（Unified Modeling Language） It's an open way , Pertaining to 、 visualization 、 Build and write a developing 、 Object oriented 、 Open methods of software intensive system products .

And my description ：
 

UML Count as Between R & D and non R & D   For business design Way of communication .

and , Before you write the code , Design must be first .

Code written without thinking ... It's thoughtless .

---

  The class diagram structure

Interface diagram structure

---

UML Class diagram Of Six relationships

Inherit 、 Realization 、 Combine 、 polymerization 、 relation 、 rely on

Each relationship has its own way of expression , That is to say Line + arrow form

Professional lines and arrows

Professional symbols  

Properties and methods “+”、“-” and “#” Indicates access level ：

 

+：public

-：private

#：protected

---

Combined with examples 、 Schematic diagram Study

Inheritance relationships

  The inheritance relationship between classes , You must be familiar with , Father and son , Inherit the father and the son .

  Icon ：

---

Realization relationship

Implementation relationship between class and interface , You must be no stranger .

  Icon ：

---

  Aggregate relationship

What is embodied is A object （ School ） Can contain B object （ teacher 、 Student ）, but B Object is not A Part of the object .

teacher 、 Student , If the school doesn't exist , They can still exist alone .

Aggregation represents a weak ‘ Have ’ Relationship .

Icon ：

---

synthetic relation

What is embodied is A object （ Phoenix ） Can contain B object （ Wing 、 Claws, etc ）.A As a whole , B As part .

If A be without ,B It's gone . The Phoenix is gone , Its wings are also equivalent to missing .

The whole and the part have the same life cycle .

Combination represents a strong ‘ Have ’ Relationship .

Icon ： 

---

Connections

Connections , Obviously, there is There are associations between classes , That's it Two way to Two way connection .

Well, for example , The connection between students and teachers , Students associate with multiple teachers , Teachers can also manage multiple students .

Of course, there are One way Association , That is, students are related to multiple courses , But the course can't actively relate to students .

Actually , There is also a connection between oneself , Self correlation .

  Icon ：

 

---

Dependency relationship  

In fact, there is a little similar correlation , however Dependency has a very personal characteristic ,

Namely Methods of one class use objects of another class as parameters .

Icon ：

 

Okay , That's all for this article .