移動開發之設計模式- 資料訪問物件模式(IOS&Android)
阿新 • • 發佈:2018-12-19
資源
完全參照資料訪問物件模式|菜鳥教程但不包括IOS程式碼
資料訪問物件模式
資料訪問物件模式(Data Access Object Pattern)或 DAO 模式用於把低階的資料訪問 API 或操作從高階的業務服務中分離出來。以下是資料訪問物件模式的參與者。
- 資料訪問物件介面(Data Access Object Interface) - 該介面定義了在一個模型物件上要執行的標準操作。
- 資料訪問物件實體類(Data Access Object concrete class) - 該類實現了上述的介面。該類負責從資料來源獲取資料,資料來源可以是資料庫,也可以是 xml,或者是其他的儲存機制。
- 模型物件/數值物件(Model Object/Value Object) - 該物件是簡單的 POJO,包含了 get/set 方法來儲存通過使用 DAO 類檢索到的資料。
Android
Student
public class Student { private String name; private int rollNo; Student(String name, int rollNo){ this.name = name; this.rollNo = rollNo; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getRollNo() { return rollNo; } public void setRollNo(int rollNo) { this.rollNo = rollNo; } }
StudentDao.java
import java.util.List;
public interface StudentDao {
public List<Student> getAllStudents();
public Student getStudent(int rollNo);
public void updateStudent(Student student);
public void deleteStudent(Student student);
}
StudentDaoImpl
import java.util.ArrayList; import java.util.List; public class StudentDaoImpl implements StudentDao { //列表是當作一個數據庫 List<Student> students; public StudentDaoImpl(){ students = new ArrayList<Student>(); Student student1 = new Student("Robert",0); Student student2 = new Student("John",1); students.add(student1); students.add(student2); } @Override public void deleteStudent(Student student) { students.remove(student.getRollNo()); System.out.println("Student: Roll No " + student.getRollNo() +", deleted from database"); } //從資料庫中檢索學生名單 @Override public List<Student> getAllStudents() { return students; } @Override public Student getStudent(int rollNo) { return students.get(rollNo); } @Override public void updateStudent(Student student) { students.get(student.getRollNo()).setName(student.getName()); System.out.println("Student: Roll No " + student.getRollNo() +", updated in the database"); } }
DaoPatternDemo
public class DaoPatternDemo {
public static void main(String[] args) {
StudentDao studentDao = new StudentDaoImpl();
//輸出所有的學生
for (Student student : studentDao.getAllStudents()) {
System.out.println("Student: [RollNo : "
+student.getRollNo()+", Name : "+student.getName()+" ]");
}
//更新學生
Student student =studentDao.getAllStudents().get(0);
student.setName("Michael");
studentDao.updateStudent(student);
//獲取學生
studentDao.getStudent(0);
System.out.println("Student: [RollNo : "
+student.getRollNo()+", Name : "+student.getName()+" ]");
}
}
結果
Student: [RollNo : 0, Name : Robert ]
Student: [RollNo : 1, Name : John ]
Student: Roll No 0, updated in the database
Student: [RollNo : 0, Name : Michael ]
IOS
Student.h
#import <Foundation/Foundation.h>
@interface Student : NSObject
@property (nonatomic, strong) NSString* name;
@property (nonatomic, assign) int rollNo;
- (instancetype)initWithName:(NSString*)name rollNo:(int)rollNo;
@end
Student.m
#import "Student.h"
@interface Student()
@end
@implementation Student
- (instancetype)initWithName:(NSString*)name rollNo:(int)rollNo
{
self = [super init];
if (self) {
self.name = name;
self.rollNo = rollNo;
}
return self;
}
- (NSString *)description
{
return [NSString stringWithFormat:@"Student: [RollNo : %d , Name : %@]", self.rollNo, self.name];
}
@end
StudentDaoImpl.h
#import <Foundation/Foundation.h>
#import "Student.h"
@protocol StudentDao <NSObject>
-(NSArray*)getAllStudents;
-(Student*)getStudent:(int)rollNo;
-(void)updateStudent:(Student*)student;
-(void)deleteStudent:(Student*)student;
@end
@interface StudentDaoImpl : NSObject <StudentDao>
@end
StudentDaoImpl.m
#import "StudentDaoImpl.h"
@interface StudentDaoImpl ()
@property (nonatomic, strong) NSMutableArray *students;
@end
@implementation StudentDaoImpl
- (instancetype)init
{
self = [super init];
if (self) {
self.students = [[NSMutableArray alloc]init];
Student *student1 = [[Student alloc] initWithName:@"Robert" rollNo:0];
Student *student2 = [[Student alloc] initWithName:@"John" rollNo:1];
[self.students addObject:student1];
[self.students addObject:student2];
}
return self;
}
- (void)deleteStudent:(Student *)student {
[self.students removeObject:student];
NSLog(@"Student: roll No %d , deleted from database.", student.rollNo);
}
- (NSArray *)getAllStudents {
//self.students removeObject:
return self.students;
}
- (Student *)getStudent:(int)rollNo {
if(rollNo <= [self.students count]) {
return [self.students objectAtIndex:rollNo];
}
return nil;
}
- (void)updateStudent:(Student *)student {
[[self.students objectAtIndex:student.rollNo] setName:student.name];
NSLog(@"Student: Roll No %d ,updated in the database.", student.rollNo);
}
@end
ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
id<StudentDao> studentDao = StudentDaoImpl.new;
//輸出所有的學生
for (Student *student in [studentDao getAllStudents]) {
NSLog(@"%@", [student description]);
}
//更新學生
Student *student = [[studentDao getAllStudents] objectAtIndex:0];
[student setName:@"Michael"];
[studentDao updateStudent:student];
//獲取學生
NSLog(@"%@", [[studentDao getStudent:0] description]);
}
結果
Student: [RollNo : 0 , Name : Robert]
Student: [RollNo : 1 , Name : John]
Student: Roll No 0 ,updated in the database.
Student: [RollNo : 0 , Name : Michael]