传输对象模式（Transfer Object Pattern）

是一种业务对象传输的实践表达。

传输对象模式的实例

定义值对象类

  1. class StudentVO {
  2.     constructor(name, rollNo){
  3.        this.name = name;
  4.        this.rollNo = rollNo;
  5.     }
  6.     getName() {
  7.        return this.name;
  8.     }
  9.     setName(name) {
  10.        this.name = name;
  11.     }
  12.     getRollNo() {
  13.        return this.rollNo;
  14.     }
  15.     setRollNo(rollNo) {
  16.        this.rollNo = rollNo;
  17.     }
  18. }

定义值对象对应的业务对象

  1. class StudentBO{
  2.     constructor(){
  3.         //列表是当作一个数据库
  4.         this.students = [];
  5.         this.students.getIndexByRollNo = (rollNo)=>{
  6.             return this.students.findIndex(
  7.                 (val)=>val.getRollNo() == rollNo
  8.             );
  9.         }
  10.         const student1 = new StudentVO("Robert",0);
  11.         const student2 = new StudentVO("John",1);
  12.         this.students.push(student1);
  13.         this.students.push(student2);    
  14.     }
  15.     deleteStudent(student) {
  16.         this.students.splice(student.getIndexByRollNo(student.getRollNo() ),1);
  17.        console.log("Student: Roll No " + student.getRollNo() 
  18.           +", deleted from database");
  19.     }
  20.     //从数据库中检索学生名单
  21.     getAllStudents() {
  22.        return this.students;
  23.     }
  24.     getStudent(rollNo) {
  25.        return this.students[this.students.getIndexByRollNo(rollNo)];
  26.     }
  28.     updateStudent(student) {
  29.         this.students[this.students.getIndexByRollNo(student.getRollNo())].setName(student.getName());
  30.        console.log("Student: Roll No " + student.getRollNo() 
  31.           +", updated in the database");
  32.     }
  33. }

获取全部业务对象，并更新传输对象

  1. const studentBusinessObject = new StudentBO();
  3. //输出所有的学生
  4. for (const student of studentBusinessObject.getAllStudents()) {
  5.     console.log("Student: [RollNo : "
  6.     +student.getRollNo()+", Name : "+student.getName()+" ]");
  7. }
  9. //更新学生
  10. const student =studentBusinessObject.getAllStudents()[
  11.     studentBusinessObject.getAllStudents().getIndexByRollNo(0)
  12. ];
  13. student.setName("Michael");
  14. studentBusinessObject.updateStudent(student);
  16. //获取学生
  17. studentBusinessObject.getStudent(0);
  18. console.log("Student: [RollNo : "
  19. +student.getRollNo()+", Name : "+student.getName()+" ]");

传输对象模式的优势

代码看起来和数据访问对象模式很像，但是表达的意思是完全不一样的。传输对象模式表达的是一种传输模型，数据访问对象模式表达的是模型层和操作层的分离。