iOS FMDB使用與緩存數據

AlberthaTin 8年前發布 | 25K 次閱讀 iOS開發 移動開發

來自： http://www.jianshu.com/p/968c381cb7d7


一、FMDB簡介

  • 什么是FMDB
    • FMDB是iOS平臺的SQLite數據庫 框架
    • FMDB以面向OC的方式封裝了SQLite的C語言API

  • FMDB優點

    • 使用起來更加面向對象，省去了很多麻煩、冗余的C語言代碼

    • 對比蘋果自帶的Core Data框架，更加輕量級和靈活
    • 提供了多線程安全的數據庫操作方法，有效地防止數據混亂

      • </ul> </li>

    • FMDB的github地址

      • https://github.com/ccgus/fmdb

        • </ul> </li>

      • 核心類

        • FMDatabase
          • 一個FMDatabase對象就代表一個單獨的SQLite數據庫
            •  <li>用來執行SQL語句</li>

 <li>FMDatabase這個類是線程不安全的，如果在多個線程中同時使用一個FMDatabase實例，會造成數據混亂等問題</li>

 <li>為了保證線程安全，FMDB提供方便快捷的FMDatabaseQueue類</li>

</ul>

            </li>

          • FMResultSet
            • 使用FMDatabase執行查詢后的結果集
              • </ul>

              </li>

            • FMDatabaseQueue
              • 用于在多線程中執行多個查詢或更新，它是線程安全的
                • </ul>

                </li>

                </ul> </li> </ul> 

                // FMDatabaseQueue的創建
FMDatabaseQueue *queue =
                

                [FMDatabaseQueue databaseQueueWithPath:path];
[queue inDatabase:^(FMDatabase*db) {
   [db executeUpdate:@"INSERTINTO t_student(name)VALUES (?)",@"Jack"];
   [db executeUpdate:@"INSERTINTO t_student(name)VALUES (?)",@"Rose"];
   [db executeUpdate:@"INSERTINTO t_student(name)VALUES (?)",@"Jim"];
                

                FMResultSetrs= [dbexecuteQuery:@"select from t_student"];
   while([rsnext]) {
        // …
   }
}];</pre> 
                   
 
                •  
                  注意：打開數據庫，文件路徑有三種情況
                  

                     
   
                  • 具體文件路徑：如果不存在會自動創建
                    • 

                  • 空字符串@""：會在臨時目錄創建一個空的數據庫，當FMDatabase連接關閉時，數據庫文件也被刪除‘ 
                  • nil：會創建一個內存中臨時數據庫，當FMDatabase連接關閉時，數據庫會被銷毀
                    • </ul>
 
                    // 通過指定SQLite數據庫文件路徑來創建FMDatabase對象
FMDatabase*db= [FMDatabase databaseWithPath:path];
if (![dbopen]) {
 NSLog(@"數據庫打開失敗！");
}
                     </li>
                    

                  •  
                    在FMDB中，除查詢以外的所有操作，都稱為“更新”：create、drop、insert、update、delete等
                    
 
                    • 
 
                  
 
                  // 使用executeUpdate:方法執行更新
- (BOOL)executeUpdate:(NSString*)sql, ...
- (BOOL)executeUpdateWithFormat:(NSString*)format,...
- (BOOL)executeUpdate:(NSString*)sqlwithArgumentsInArray:(NSArray*)arguments
                   
                     
 
                  • 執行查詢
                    • 
 
                  
 
                  - (FMResultSet*)executeQuery:(NSString*)sql, ...
- (FMResultSet*)executeQueryWithFormat:(NSString*)format,...
- (FMResultSet*)executeQuery:(NSString*)sqlwithArgumentsInArray:(NSArray*)arguments
                   
                  二、CoreData 與 FMDB
                  
 
                     
 
                  • coreData：自動生成SQL語句，不能自己設置，個性化的、優化的等SQL語句不能實現
                  • FMDB：可以自己定制不同的SQL語句，擴展性好
                    • 
 
                  
 
                  三、FMDB實例 基本使用
                  
 
                     
 
                  • 1.導入FMDB框架到項目中
                  • 2.使用FMDB
                    • 
 </ul>
 
                    # 二、增刪改查
                    

                      

                    • 數據庫操作都放在queue中的，queue中操作database，線程是安全的
                      • 

                    

                    ```objc
                    

                    import "JPViewController.h"
                    

                    import "FMDB.h"
                    

                    @interface JPViewController ()
@property (nonatomic, strong) FMDatabase *db;
@end
                    

                    @implementation JPViewController
                    

                      

                    • (void)viewDidLoad
{
  [super viewDidLoad];
                      

                      // 1.獲得數據庫文件的路徑
  NSString doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
  NSString filename = [doc stringByAppendingPathComponent:@"students.sqlite"];
                      

                      // 2.得到數據庫
  FMDatabase *db = [FMDatabase databaseWithPath:filename];
                      

                      // 3.打開數據庫
  if ([db open]) {
                      


                        // 4.創表
  BOOL result = [db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_student (id integer PRIMARY KEY AUTOINCREMENT, name text NOT NULL, age integer NOT NULL);"];
  if (result) {
      NSLog(@"成功創表");
  } else {
      NSLog(@"創表失敗");
  }

                      

                      }
                      

                      self.db = db;
}
                      

                      • 

                    • (void)touchesBegan:(NSSet )touches withEvent:(UIEvent )event
{
  [self delete];
  [self insert];
  [self query];
}
                      

                      • 

                    • (void)insert
{
  for (int i = 0; i<10; i++) {
                      


                        NSString *name = [NSString stringWithFormat:@"jack-%d", arc4random_uniform(100)];
  // executeUpdate : 不確定的參數用?來占位，參數都必須是對象
  [self.db executeUpdate:@"INSERT INTO t_student (name, age) VALUES (?, ?);", name, @(arc4random_uniform(40))];

                      

                      //        [self.db executeUpdate:@"INSERT INTO t_student (name, age) VALUES (?, ?);" withArgumentsInArray:@[name, @(arc4random_uniform(40))]]; // ?方式，參數要是對象，不是對象要包裝為對象
                      


                        // executeUpdateWithFormat : format方式拼接，不確定的參數用%@、%d等來占位

                      

                      //        [self.db executeUpdateWithFormat:@"INSERT INTO t_student (name, age) VALUES (%@, %d);", name, arc4randomuniform(40)];
// 注意：如果直接寫%@不用加單引號兩邊，會自動加單引號兩邊，如果'jack%d'的兩邊不加單引號就會報錯，所以要注意
   [self.db executeUpdateWithFormat:@"INSERT INTO tstudent (name, age) VALUES ('jack%d', %d);", name, arc4random_uniform(40)]; 
  }
}
                      

                      • 

                    • (void)delete
{
//    [self.db executeUpdate:@"DELETE FROM t_student;"];
  [self.db executeUpdate:@"DROP TABLE IF EXISTS t_student;"];
  [self.db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_student (id integer PRIMARY KEY AUTOINCREMENT, name text NOT NULL, age integer NOT NULL);"];
}
                      

                      • 

                    • (void)query
{
  // 1.執行查詢語句
  FMResultSet resultSet = [self.db executeQuery:@"SELECT  FROM t_student"];
                      

                      // 2.遍歷結果
  while ([resultSet next]) {
                      


                        int ID = [resultSet intForColumn:@"id"];
  NSString *name = [resultSet stringForColumn:@"name"];
  int age = [resultSet intForColumn:@"age"];
  NSLog(@"%d %@ %d", ID, name, age);

                      

                      }
}
@end</pre> 
                      +  事務操作
                      

                      • 

                    

                    ```objc
                    

                    import "JPViewController.h"
                    

                    import "FMDB.h" // 導入頭文件
                    

                    @interface JPViewController ()
@property (nonatomic, strong) FMDatabaseQueue *queue;
@end
                    

                    @implementation JPViewController
                    

                      

                    • (void)viewDidLoad
{
  [super viewDidLoad];
                      

                      // 1.獲得數據庫文件的路徑
  NSString doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
  NSString filename = [doc stringByAppendingPathComponent:@"persons.sqlite"];
                      

                      // 2.得到數據庫
  FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:filename];
                      

                      // 3.打開數據庫
  [queue inDatabase:^(FMDatabase *db) {
                      


                        // 4.創表
  BOOL result = [db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_person (id integer PRIMARY KEY AUTOINCREMENT, name text NOT NULL, age integer NOT NULL);"];
  if (result) {
      NSLog(@"成功創表");
  } else {
      NSLog(@"創表失敗");
  }

                      

                      }];
                      

                      self.queue = queue;
}
                      

                      • 

                    

                    // 事務操作：錯誤會回滾
                    

                      

                    • (void)touchesBegan:(NSSet )touches withEvent:(UIEvent )event
{
//    [self.queue inDatabase:^(FMDatabase *db) {
//        [db beginTransaction];
//
                      
//        [db executeUpdate:@"INSERT INTO t_person (name, age) VALUES (?, ?);", @"jake", @30];
//        [db executeUpdate:@"INSERT INTO t_person (name, age) VALUES (?, ?);", @"jake", @30];
//        [db executeUpdate:@"INSERT INTO t_person (name, age) VALUES (?, ?);", @"jake", @30];
//        [db executeUpdate:@"INSERT INTO t_person (name, age) VALUES (?, ?);", @"jake", @30];
//
                      
//        [db commit];
//    }];
                      • 

                    

                    //    [self.queue inTransaction:^(FMDatabase db, BOOL rollback) {
//        [db executeUpdate:@"INSERT INTO t_person (name, age) VALUES (?, ?);", @"jake", @30];
//        [db executeUpdate:@"INSERT INTO t_person (name, age) VALUES (?, ?);", @"jake", @30];
//        [db executeUpdate:@"INSERT INTO t_person (name, age) VALUES (?, ?);", @"jake", @30];
//        [db executeUpdate:@"INSERT INTO t_person (name, age) VALUES (?, ?);", @"jake", @30];
//    }];
                    

                    }
@end</pre> 
                    四、FMDB緩存數據
                    
 
                    #import "JPStatusTool.h"
                    

                    import "JPHttpTool.h"
                    

                    import "MJExtension.h"
                    

                    import "FMDB.h"
                    

                    import "JPStatus.h"
                    

                    @implementation JPStatusTool
                    

                    /* 數據庫實例 /
static FMDatabase *_db;
                    

                      

                    • (void)initialize
{
  // 1.獲得數據庫文件的路徑
  NSString doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
  NSString filename = [doc stringByAppendingPathComponent:@"status.sqlite"];
                      

                      // 2.得到數據庫
  _db = [FMDatabase databaseWithPath:filename];
                      

                      // 3.打開數據庫
  if ([_db open]) {
                      


                        // 4.創表
  BOOL result = [_db executeUpdate:@"CREATE TABLE IF NOT EXISTS t_home_status (id integer PRIMARY KEY AUTOINCREMENT, access_token text NOT NULL, status_idstr text NOT NULL, status_dict blob NOT NULL);"];
  if (result) {
      NSLog(@"成功創表");
  } else {
      NSLog(@"創表失敗");
  }

                      

                      }
}
                      

                      • 

                    • (void)homeStatusesWithParam:(JPHomeStatusesParam )param success:(void (^)(JPHomeStatusesResult ))success failure:(void (^)(NSError *))failure
{
//    param.count = @5;
                      

                      // 從數據庫中讀取（加載）緩存數據(微博模型數組)
  NSArray *cachedHomeStatuses = [self cachedHomeStatusesWithParam:param];
  if (cachedHomeStatuses.count != 0) { // 有緩存數據
                      


                        if (success) {
      JPHomeStatusesResult *result = [[JPHomeStatusesResult alloc] init];
      result.statuses = cachedHomeStatuses;
      success(result);
  }

                      

                      } else { // 沒有緩存數據
                      


                        NSDictionary *params = [param keyValues];

  [JPHttpTool get:@"https://api.weibo.com/2/statuses/home_timeline.json" params:params success:^(id responseObj) {
      // 新浪返回的字典數組
      NSArray *statusDictArray = responseObj[@"statuses"];

      // 緩存微博字典數組
      [self saveHomeStatusDictArray:statusDictArray accessToken:param.access_token];

      if (success) {
          JPHomeStatusesResult *result = [JPHomeStatusesResult objectWithKeyValues:responseObj];
          success(result);
      }
  } failure:^(NSError *error) {
      if (failure) {
          failure(error);
      }
  }];

                      

                      }
}
                      

                      • 

                    

                    /**
                    

                      

                    • 通過請求參數去數據庫中加載對應的微博數據
*
                      • 

                    • @param param 請求參數
*/
                      

                        

                      • (NSArray )cachedHomeStatusesWithParam:(JPHomeStatusesParam )param
{
// 創建數組緩存微博數據
NSMutableArray *statuses = [NSMutableArray array];
                        • 

                      

                      // 根據請求參數查詢數據
FMResultSet *resultSet = nil;
if (param.since_id) {
                      


                      resultSet = [_db executeQuery:@"SELECT * FROM t_home_status WHERE access_token = ? AND status_idstr > ? ORDER BY status_idstr DESC limit ?;", param.access_token, param.since_id, param.count];

                      

                      } else if (param.max_id) {
                      


                      resultSet = [_db executeQuery:@"SELECT * FROM t_home_status WHERE access_token = ? AND status_idstr <= ? ORDER BY status_idstr DESC limit ?;", param.access_token, param.max_id, param.count];

                      

                      } else {
                      


                      resultSet = [_db executeQuery:@"SELECT * FROM t_home_status WHERE access_token = ? ORDER BY status_idstr DESC limit ?;", param.access_token, param.count];

                      

                      }
                      

                      // 遍歷查詢結果
while (resultSet.next) {
                      


                      NSData *statusDictData = [resultSet objectForColumnName:@"status_dict"];
NSDictionary *statusDict = [NSKeyedUnarchiver unarchiveObjectWithData:statusDictData];
// 字典轉模型
JPStatus *status = [JPStatus objectWithKeyValues:statusDict];
// 添加模型到數組中
[statuses addObject:status];

                      

                      }
                      

                      return statuses;
}
                      

                      • 

                    

                    /**
                    

                      

                    • 緩存微博字典數組到數據庫中
*/
                        

                      • (void)saveHomeStatusDictArray:(NSArray )statusDictArray accessToken:(NSString )accessToken
{
for (NSDictionary statusDict in statusDictArray) {
  // 把statusDict字典對象序列化成NSData二進制數據
  NSData data = [NSKeyedArchiver archivedDataWithRootObject:statusDict];
  [_db executeUpdate:@"INSERT INTO t_home_status (access_token, status_idstr, status_dict) VALUES (?, ?, ?);",
   accessToken, statusDict[@"idstr"], data];
}
}
@end</pre>
                        • 

                      

                      •
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