iOS FMDB使用与缓存数据

AlberthaTin 9年前

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

一、FMDB简介

什么是FMDB

FMDB是iOS平台的SQLite数据库 框架
FMDB以面向OC的方式封装了SQLite的C语言API

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FMDB优点
- 使用起来更加面向对象，省去了很多麻烦、冗余的C语言代码
- 对比苹果自带的Core Data框架，更加轻量级和灵活
- 提供了多线程安全的数据库操作方法，有效地防止数据混乱
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FMDB的github地址

https://github.com/ccgus/fmdb

核心类

FMDatabase

一个FMDatabase对象就代表一个单独的SQLite数据库
用来执行SQL语句
FMDatabase这个类是线程不安全的，如果在多个线程中同时使用一个FMDatabase实例，会造成数据混乱等问题
为了保证线程安全，FMDB提供方便快捷的FMDatabaseQueue类

FMResultSet

使用FMDatabase执行查询后的结果集

FMDatabaseQueue

用于在多线程中执行多个查询或更新，它是线程安全的

// FMDatabaseQueue的创建  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"];       FMResultSet*rs= [dbexecuteQuery:@"select* from t_student"];     while([rsnext]) {          // …     }  }];

注意：打开数据库，文件路径有三种情况
- 具体文件路径：如果不存在会自动创建
- 空字符串@""：会在临时目录创建一个空的数据库，当FMDatabase连接关闭时，数据库文件也被删除‘
- nil：会创建一个内存中临时数据库，当FMDatabase连接关闭时，数据库会被销毁
```
// 通过指定SQLite数据库文件路径来创建FMDatabase对象  FMDatabase*db= [FMDatabase databaseWithPath:path];  if (![dbopen]) {   NSLog(@"数据库打开失败！");  }
```
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在FMDB中，除查询以外的所有操作，都称为“更新”：create、drop、insert、update、delete等

// 使用executeUpdate:方法执行更新  - (BOOL)executeUpdate:(NSString*)sql, ...  - (BOOL)executeUpdateWithFormat:(NSString*)format,...  - (BOOL)executeUpdate:(NSString*)sqlwithArgumentsInArray:(NSArray*)arguments

执行查询

- (FMResultSet*)executeQuery:(NSString*)sql, ...  - (FMResultSet*)executeQueryWithFormat:(NSString*)format,...  - (FMResultSet*)executeQuery:(NSString*)sqlwithArgumentsInArray:(NSArray*)arguments

二、CoreData 与 FMDB

coreData：自动生成SQL语句，不能自己设置，个性化的、优化的等SQL语句不能实现
FMDB：可以自己定制不同的SQL语句，扩展性好

三、FMDB实例基本使用

1.导入FMDB框架到项目中
2.使用FMDB

# 二、增删改查  + 数据库操作都放在queue中的，queue中操作database，线程是安全的    ```objc  #import "JPViewController.h"  #import "FMDB.h"    @interface JPViewController ()  @property (nonatomic, strong) FMDatabase *db;  @end    @implementation JPViewController    - (void)viewDidLoad  {      [super viewDidLoad];        // 1.获得数据库文件的路径      NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];      NSString *filename = [doc stringByAppendingPathComponent:@"students.sqlite"];        // 2.得到数据库      FMDatabase *db = [FMDatabase databaseWithPath:filename];        // 3.打开数据库      if ([db open]) {          // 4.创表          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(@"成功创表");          } else {              NSLog(@"创表失败");          }      }        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 : 不确定的参数用?来占位，参数都必须是对象          [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，参数要是对象，不是对象要包装为对象            // executeUpdateWithFormat : format方式拼接，不确定的参数用%@、%d等来占位  //        [self.db executeUpdateWithFormat:@"INSERT INTO t_student (name, age) VALUES (%@, %d);", name, arc4random_uniform(40)];  // 注意：如果直接写%@不用加单引号两边，会自动加单引号两边，如果'jack_%d'的两边不加单引号就会报错，所以要注意       [self.db executeUpdateWithFormat:@"INSERT INTO t_student (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.执行查询语句      FMResultSet *resultSet = [self.db executeQuery:@"SELECT * FROM t_student"];        // 2.遍历结果      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

+  事务操作    ```objc  #import "JPViewController.h"  #import "FMDB.h" // 导入头文件    @interface JPViewController ()  @property (nonatomic, strong) FMDatabaseQueue *queue;  @end    @implementation JPViewController    - (void)viewDidLoad  {      [super viewDidLoad];        // 1.获得数据库文件的路径      NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];      NSString *filename = [doc stringByAppendingPathComponent:@"persons.sqlite"];        // 2.得到数据库      FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:filename];        // 3.打开数据库      [queue inDatabase:^(FMDatabase *db) {          // 4.创表          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(@"成功创表");          } else {              NSLog(@"创表失败");          }      }];        self.queue = queue;  }    // 事务操作：错误会回滚  - (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

四、FMDB缓存数据

#import "JPStatusTool.h"  #import "JPHttpTool.h"  #import "MJExtension.h"  #import "FMDB.h"  #import "JPStatus.h"    @implementation JPStatusTool    /** 数据库实例 */  static FMDatabase *_db;    + (void)initialize  {      // 1.获得数据库文件的路径      NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];      NSString *filename = [doc stringByAppendingPathComponent:@"status.sqlite"];        // 2.得到数据库      _db = [FMDatabase databaseWithPath:filename];        // 3.打开数据库      if ([_db open]) {          // 4.创表          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(@"成功创表");          } else {              NSLog(@"创表失败");          }      }  }    + (void)homeStatusesWithParam:(JPHomeStatusesParam *)param success:(void (^)(JPHomeStatusesResult *))success failure:(void (^)(NSError *))failure  {  //    param.count = @5;        // 从数据库中读取（加载）缓存数据(微博模型数组)      NSArray *cachedHomeStatuses = [self cachedHomeStatusesWithParam:param];      if (cachedHomeStatuses.count != 0) { // 有缓存数据          if (success) {              JPHomeStatusesResult *result = [[JPHomeStatusesResult alloc] init];              result.statuses = cachedHomeStatuses;              success(result);          }      } else { // 没有缓存数据          NSDictionary *params = [param keyValues];            [JPHttpTool get:@"https://api.weibo.com/2/statuses/home_timeline.json" params:params success:^(id responseObj) {              // 新浪返回的字典数组              NSArray *statusDictArray = responseObj[@"statuses"];                // 缓存微博字典数组              [self saveHomeStatusDictArray:statusDictArray accessToken:param.access_token];                if (success) {                  JPHomeStatusesResult *result = [JPHomeStatusesResult objectWithKeyValues:responseObj];                  success(result);              }          } failure:^(NSError *error) {              if (failure) {                  failure(error);              }          }];      }  }    /**   *  通过请求参数去数据库中加载对应的微博数据   *   *  @param param 请求参数   */  + (NSArray *)cachedHomeStatusesWithParam:(JPHomeStatusesParam *)param  {      // 创建数组缓存微博数据      NSMutableArray *statuses = [NSMutableArray array];        // 根据请求参数查询数据      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];      }        // 遍历查询结果      while (resultSet.next) {          NSData *statusDictData = [resultSet objectForColumnName:@"status_dict"];          NSDictionary *statusDict = [NSKeyedUnarchiver unarchiveObjectWithData:statusDictData];          // 字典转模型          JPStatus *status = [JPStatus objectWithKeyValues:statusDict];          // 添加模型到数组中          [statuses addObject:status];      }        return statuses;  }    /**   *  缓存微博字典数组到数据库中   */  + (void)saveHomeStatusDictArray:(NSArray *)statusDictArray accessToken:(NSString *)accessToken  {      for (NSDictionary *statusDict in statusDictArray) {          // 把statusDict字典对象序列化成NSData二进制数据          NSData *data = [NSKeyedArchiver archivedDataWithRootObject:statusDict];          [_db executeUpdate:@"INSERT INTO t_home_status (access_token, status_idstr, status_dict) VALUES (?, ?, ?);",           accessToken, statusDict[@"idstr"], data];      }  }  @end

iOS FMDB使用与缓存数据

一、FMDB简介

二、CoreData 与 FMDB

三、FMDB实例 基本使用

四、FMDB缓存数据

相关经验

目录

三、FMDB实例基本使用