Iphone數據庫操作

iPhone 中使用名爲 SQLite 的數據庫管理系統。它是一款輕型的數據庫，是遵守ACID的關聯式數據庫管理系統，它的設計目標是嵌入式的，而且目前已經在很多嵌入式產品中使用了它，它佔用資源非常的低，在嵌入式設備中，可能只需要幾百K的內存就夠了。它能夠支持Windows/Linux/Unix等等主流的操作系統，同時能夠跟很多程序語言相結合，比如 Tcl、PHP、Java 等，還有 ODBC 接口，同樣比起 Mysql、PostgreSQL 這兩款開源世界著名的數據庫管理系統來講，它的處理速度比他們都快。

    其使用步驟大致分爲以下幾步：

   1. 創建DB文件和表格
   2. 添加必須的庫文件(FMDB for iPhone, libsqlite3.0.dylib)
   3. 通過 FMDB 的方法使用 SQLite

創建DB文件和表格

$ sqlite3 sample.db
sqlite> CREATE TABLE TEST(
   ...>  id INTEGER PRIMARY KEY,
   ...>  name VARCHAR(255)
   ...> );

    簡單地使用上面的語句生成數據庫文件後，用一個圖形化SQLite管理工具，比如 Lita 來管理還是很方便的。

    然後將文件(sample.db)添加到工程中。

添加必須的庫文件(FMDB for iPhone, libsqlite3.0.dylib)

    首先添加 Apple 提供的 sqlite 操作用程序庫 ibsqlite3.0.dylib 到工程中。位置如下

/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS${VER}.sdk/usr/lib/libsqlite3.0.dylib

    這樣一來就可以訪問數據庫了，但是爲了更加方便的操作數據庫，這裏使用 FMDB for iPhone。

svn co http://flycode.googlecode.com/svn/trunk/fmdb fmdb

    如上下載該庫，並將以下文件添加到工程文件中：

FMDatabase.h
FMDatabase.m
FMDatabaseAdditions.h
FMDatabaseAdditions.m
FMResultSet.h
FMResultSet.m

通過 FMDB 的方法使用 SQLite

    使用 SQL 操作數據庫的代碼在程序庫的 fmdb.m 文件中大部分都列出了、只是連接數據庫文件的時候需要注意 — 執行的時候，參照的數據庫路徑位於 Document 目錄下，之前把剛纔的 sample.db 文件拷貝過去就好了。

位置如下
/Users/xxxx/Library/Application Support/iPhone Simulator/User/Applications/xxxx/Documents/sample.db

    以下爲鏈接數據庫時的代碼：

BOOL success;
NSError *error;
NSFileManager *fm = [NSFileManager defaultManager];
NSArray  *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *writableDBPath = [documentsDirectory stringByAppendingPathComponent:@"sample.db"];
success = [fm fileExistsAtPath:writableDBPath];
if(!success){
  NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"sample.db"];
  success = [fm copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
  if(!success){
    NSLog([error localizedDescription]);
  }
}

// 連接DB
FMDatabase* db = [FMDatabase databaseWithPath:writableDBPath];
if ([db open]) {
  [db setShouldCacheStatements:YES];

  // INSERT
  [db beginTransaction];
  int i = 0;
  while (i++ < 20) {
    [db executeUpdate:@"INSERT INTO TEST (name) values (?)" , [NSString stringWithFormat:@"number %d", i]];
    if ([db hadError]) {
      NSLog(@"Err %d: %@", [db lastErrorCode], [db lastErrorMessage]);
    }
  }
  [db commit];

  // SELECT
  FMResultSet *rs = [db executeQuery:@"SELECT * FROM TEST"];
  while ([rs next]) {
    NSLog(@"%d %@", [rs intForColumn:@"id"], [rs stringForColumn:@"name"]);
  }
  [rs close];
  [db close];
}else{
  NSLog(@"Could not open db.");
}

    接下來再看看用 DAO 的形式來訪問數據庫的使用方法，代碼整體構造如下。

    首先創建如下格式的數據庫文件：

$ sqlite3 sample.db
sqlite> CREATE TABLE TbNote(
   ...>  id INTEGER PRIMARY KEY,
   ...>  title VARCHAR(255),
   ...>  body VARCHAR(255)
   ...> );

創建DTO（Data Transfer Object）

//TbNote.h
#import <Foundation/Foundation.h>

@interface TbNote : NSObject {
  int index;
  NSString *title;
  NSString *body;
}

@property (nonatomic, retain) NSString *title;
@property (nonatomic, retain) NSString *body;

- (id)initWithIndex:(int)newIndex Title:(NSString *)newTitle Body:(NSString *)newBody;
- (int)getIndex;

@end

//TbNote.m
#import "TbNote.h"

@implementation TbNote
@synthesize title, body;

- (id)initWithIndex:(int)newIndex Title:(NSString *)newTitle Body:(NSString *)newBody{
  if(self = [super init]){
    index = newIndex;
    self.title = newTitle;
    self.body = newBody;
  }
  return self;
}

- (int)getIndex{
  return index;
}

- (void)dealloc {
  [title release];
  [body release];
  [super dealloc];
}

@end

創建DAO（Data Access Objects）

    這裏將 FMDB 的函數調用封裝爲 DAO 的方式。

//BaseDao.h
#import <Foundation/Foundation.h>

@class FMDatabase;

@interface BaseDao : NSObject {
  FMDatabase *db;
}

@property (nonatomic, retain) FMDatabase *db;

-(NSString *)setTable:(NSString *)sql;

@end

//BaseDao.m
#import "SqlSampleAppDelegate.h"
#import "FMDatabase.h"
#import "FMDatabaseAdditions.h"
#import "BaseDao.h"

@implementation BaseDao
@synthesize db;

- (id)init{
  if(self = [super init]){
    // 由 AppDelegate 取得打開的數據庫
    SqlSampleAppDelegate *appDelegate = (SqlSampleAppDelegate *)[[UIApplication sharedApplication] delegate];
    db = [[appDelegate db] retain];
  }
  return self;
}
// 子類中實現
-(NSString *)setTable:(NSString *)sql{
  return NULL;
}

- (void)dealloc {
  [db release];
  [super dealloc];
}

@end

    下面是訪問 TbNote 表格的類。

//TbNoteDao.h
#import <Foundation/Foundation.h>
#import "BaseDao.h"

@interface TbNoteDao : BaseDao {
}

-(NSMutableArray *)select;
-(void)insertWithTitle:(NSString *)title Body:(NSString *)body;
-(BOOL)updateAt:(int)index Title:(NSString *)title Body:(NSString *)body;
-(BOOL)deleteAt:(int)index;

@end

//TbNoteDao.m
#import "FMDatabase.h"
#import "FMDatabaseAdditions.h"
#import "TbNoteDao.h"
#import "TbNote.h"

@implementation TbNoteDao

-(NSString *)setTable:(NSString *)sql{
  return [NSString stringWithFormat:sql,  @"TbNote"];
}
// SELECT
-(NSMutableArray *)select{
  NSMutableArray *result = [[[NSMutableArray alloc] initWithCapacity:0] autorelease];
  FMResultSet *rs = [db executeQuery:[self setTable:@"SELECT * FROM %@"]];
  while ([rs next]) {
    TbNote *tr = [[TbNote alloc]
              initWithIndex:[rs intForColumn:@"id"]
              Title:[rs stringForColumn:@"title"]
              Body:[rs stringForColumn:@"body"]
              ];
    [result addObject:tr];
    [tr release];
  }
  [rs close];
  return result;
}
// INSERT
-(void)insertWithTitle:(NSString *)title Body:(NSString *)body{
  [db executeUpdate:[self setTable:@"INSERT INTO %@ (title, body) VALUES (?,?)"], title, body];
  if ([db hadError]) {
    NSLog(@"Err %d: %@", [db lastErrorCode], [db lastErrorMessage]);
  }
}
// UPDATE
-(BOOL)updateAt:(int)index Title:(NSString *)title Body:(NSString *)body{
  BOOL success = YES;
  [db executeUpdate:[self setTable:@"UPDATE %@ SET title=?, body=? WHERE id=?"], title, body, [NSNumber numberWithInt:index]];
  if ([db hadError]) {
    NSLog(@"Err %d: %@", [db lastErrorCode], [db lastErrorMessage]);
    success = NO;
  }
  return success;
}
// DELETE
- (BOOL)deleteAt:(int)index{
  BOOL success = YES;
  [db executeUpdate:[self setTable:@"DELETE FROM %@ WHERE id = ?"], [NSNumber numberWithInt:index]];
  if ([db hadError]) {
    NSLog(@"Err %d: %@", [db lastErrorCode], [db lastErrorMessage]);
    success = NO;
  }
  return success;
}

- (void)dealloc {
  [super dealloc];
}

@end

    爲了確認程序正確，我們添加一個 UITableView。使用 initWithNibName 測試 DAO。

//NoteController.h
#import <UIKit/UIKit.h>

@class TbNoteDao;

@interface NoteController : UIViewController <UITableViewDataSource, UITableViewDelegate>{
  UITableView *myTableView;
  TbNoteDao *tbNoteDao;
  NSMutableArray *record;
}

@property (nonatomic, retain) UITableView *myTableView;
@property (nonatomic, retain) TbNoteDao *tbNoteDao;
@property (nonatomic, retain) NSMutableArray *record;

@end

//NoteController.m
#import "NoteController.h"
#import "TbNoteDao.h"
#import "TbNote.h"

@implementation NoteController
@synthesize myTableView, tbNoteDao, record;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
  if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
    tbNoteDao = [[TbNoteDao alloc] init];
    [tbNoteDao insertWithTitle:@"TEST TITLE" Body:@"TEST BODY"];
//    [tbNoteDao updateAt:1 Title:@"UPDATE TEST" Body:@"UPDATE BODY"];
//    [tbNoteDao deleteAt:1];
    record = [[tbNoteDao select] retain];
  }
  return self;
}

- (void)viewDidLoad {
  [super viewDidLoad];
  myTableView = [[UITableView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
  myTableView.delegate = self;
  myTableView.dataSource = self;
  self.view = myTableView;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
  return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
  return [record count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
  static NSString *CellIdentifier = @"Cell";

  UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
  if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
  }
  TbNote *tr = (TbNote *)[record objectAtIndex:indexPath.row];
  cell.text = [NSString stringWithFormat:@"%i %@", [tr getIndex], tr.title];
  return cell;
}

- (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
}

- (void)dealloc {
  [super dealloc];
}

@end

    最後我們開看看連接DB，和添加 ViewController 的處理。這一同樣不使用 Interface Builder。

//SqlSampleAppDelegate.h
#import <UIKit/UIKit.h>

@class FMDatabase;

@interface SqlSampleAppDelegate : NSObject <UIApplicationDelegate> {
  UIWindow *window;
  FMDatabase *db;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) FMDatabase *db;

- (BOOL)initDatabase;
- (void)closeDatabase;

@end

//SqlSampleAppDelegate.m
#import "SqlSampleAppDelegate.h"
#import "FMDatabase.h"
#import "FMDatabaseAdditions.h"
#import "NoteController.h"

@implementation SqlSampleAppDelegate

@synthesize window;
@synthesize db;

- (void)applicationDidFinishLaunching:(UIApplication *)application {
  if (![self initDatabase]){
    NSLog(@"Failed to init Database.");
  }
  NoteController *ctrl = [[NoteController alloc] initWithNibName:nil bundle:nil];
  [window addSubview:ctrl.view];
  [window makeKeyAndVisible];
}

- (BOOL)initDatabase{
  BOOL success;
  NSError *error;
  NSFileManager *fm = [NSFileManager defaultManager];
  NSArray  *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *documentsDirectory = [paths objectAtIndex:0];
  NSString *writableDBPath = [documentsDirectory stringByAppendingPathComponent:@"sample.db"];

  success = [fm fileExistsAtPath:writableDBPath];
  if(!success){
    NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"sample.db"];
    success = [fm copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
    if(!success){
      NSLog([error localizedDescription]);
    }
    success = NO;
  }
  if(success){
    db = [[FMDatabase databaseWithPath:writableDBPath] retain];
    if ([db open]) {
      [db setShouldCacheStatements:YES];
    }else{
      NSLog(@"Failed to open database.");
      success = NO;
    }
  }
  return success;
}

- (void) closeDatabase{
  [db close];
}

- (void)dealloc {
  [db release];
  [window release];
  [super dealloc];
}

@end