FMDB介紹
FMDB是iOS平臺的SQLite數據庫框架
FMDB以OC的方式封裝了SQLite的C語言API
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
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
FMDB基本使用
FMDB GitHub鏈接: https://github.com/ccgus/fmdb
1.導入FMDB文件
2.導入系統依賴庫sqlite3.0.tbd
創建數據庫并打開
/*
1. 如果該路徑下已經存在該數據庫，直接獲取該數據庫;
2. 如果不存在就創建一個新的數據庫;
3. 如果傳@""，會在臨時目錄創建一個空的數據庫，當數據庫關閉時，數據庫文件也被刪除;
4. 如果傳nil，會在內存中臨時創建一個空的數據庫，當數據庫關閉時，數據庫文件也被刪除;
*/
+ (FMDatabase *)databaseWithPath:(NSString *)filePath;
// 1.獲得數據庫文件的路徑
NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filename = [doc stringByAppendingPathComponent:@"my.sqlite"];
// 2.得到數據庫
FMDatabase* db = [FMDatabase databaseWithPath:filename];
// 3.打開數據庫
if ([db open]) {
NSLog(@"打開數據庫成功");
}else {
NSLog(@"打開數據庫失敗");
}
執行更新
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
/* 執行更新的SQL語句，字符串里面的"?"，依次用后面的參數替代，必須是對象，不能是int等基本類型 */
- (BOOL)executeUpdate:(NSString *)sql,... ;
/* 執行更新的SQL語句，可以使用字符串的格式化進行構建SQL語句 */
- (BOOL)executeUpdateWithFormat:(NSString*)format,... ;
/* 執行更新的SQL語句，字符串中有"?"，依次用arguments的元素替代 */
- (BOOL)executeUpdate:(NSString*)sql withArgumentsInArray:(NSArray *)arguments;
/* 1. 直接使用完整的SQL更新語句 */
[database executeUpdate:@"insert into mytable(num,name,sex) values(0,'liuting','m');"];
NSString *sql = @"insert into mytable(num,name,sex) values(?,?,?);";
/* 2. 使用不完整的SQL更新語句，里面含有待定字符串"?"，需要后面的參數進行替代 */
[database executeUpdate:sql,@0,@"liuting",@"m"];
/* 3. 使用不完整的SQL更新語句，里面含有待定字符串"?"，需要數組參數里面的參數進行替代 */
[database executeUpdate:sql
withArgumentsInArray:@[@0,@"liuting",@"m"]];
/* 4. SQL語句字符串可以使用字符串格式化，這種我們應該比較熟悉 */
[database executeUpdateWithFormat:@"insert into mytable(num,name,sex) values(%d,%@,%@);",0,@"liuting","m"];
執行查詢
- (FMResultSet *)executeQuery:(NSString*)sql, ...
- (FMResultSet *)executeQueryWithFormat:(NSString*)format, ...
- (FMResultSet *)executeQuery:(NSString *)sql withArgumentsInArray:(NSArray *)arguments
- 處理結果FMResultSet的方法
/* 獲取下一個記錄 */
- (BOOL)next;
/* 獲取記錄有多少列 */
- (int)columnCount;
/* 通過列名得到列序號，通過列序號得到列名 */
- (int)columnIndexForName:(NSString *)columnName;
- (NSString *)columnNameForIndex:(int)columnIdx;
/* 獲取存儲的整形值 */
- (int)intForColumn:(NSString *)columnName;
- (int)intForColumnIndex:(int)columnIdx;
/* 獲取存儲的長整形值 */
- (long)longForColumn:(NSString *)columnName;
- (long)longForColumnIndex:(int)columnIdx;
/* 獲取存儲的布爾值 */
- (BOOL)boolForColumn:(NSString *)columnName;
- (BOOL)boolForColumnIndex:(int)columnIdx;
/* 獲取存儲的浮點值 */
- (double)doubleForColumn:(NSString *)columnName;
- (double)doubleForColumnIndex:(int)columnIdx;
/* 獲取存儲的字符串 */
- (NSString *)stringForColumn:(NSString *)columnName;
- (NSString *)stringForColumnIndex:(int)columnIdx;
/* 獲取存儲的日期數據 */
- (NSDate *)dateForColumn:(NSString *)columnName;
- (NSDate *)dateForColumnIndex:(int)columnIdx;
/* 獲取存儲的二進制數據 */
- (NSData *)dataForColumn:(NSString *)columnName;
- (NSData *)dataForColumnIndex:(int)columnIdx;
/* 獲取存儲的UTF8格式的C語言字符串 */
- (const unsigned cahr *)UTF8StringForColumnName:(NSString *)columnName;
- (const unsigned cahr *)UTF8StringForColumnIndex:(int)columnIdx;
/* 獲取存儲的對象，只能是NSNumber、NSString、NSData、NSNull */
- (id)objectForColumnName:(NSString *)columnName;
- (id)objectForColumnIndex:(int)columnIdx;
- 如何使用
+ (NSArray *)shops
{// 得到結果集
FMResultSet *set = [_db executeQuery:@"SELECT * FROM t_shop;"];
// 不斷往下取數據
NSMutableArray *shops = [NSMutableArray array];
while (set.next) {
// 獲得當前所指向的數據
HMShop *shop = [[HMShop alloc] init];
shop.name = [set stringForColumn:@"name"];
shop.price = [set doubleForColumn:@"price"];
[shops addObject:shop];
}
return shops;
}
- 關閉數據庫
[_db close];
FMDabaseQueue的使用
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
為了保證線程安全，FMDB提供方便快捷的FMDatabaseQueue類
創建FMDabaseQueue
NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"shops.sqlite"];
FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:path];
使用FMDabaseQueue
[queue inDatabase:^(FMDatabase*db) {
//插入記錄到表中
NSString *sqlStr = @"CREATE TABLE IF NOT EXISTS t_shop (id integer PRIMARY KEY, name text NOT NULL, price real);"；
BOOL result = [db executeUpdate:sqlStr];
if (!result) {
NSLog(@"error when insert into database table");
[db close];
}
}];
事務
事務，是指作為單個邏輯工作單元執行的一系列操作，要么完整地執行，要么完全地不執行。
比如你要更新數據庫的大量數據，我們需要確保所有的數據更新成功才行，如果在更新期間出現錯誤，就不好辦了。如果我們不使用事務，我們的更新操作直接對每個記錄生效，萬一遇到更新錯誤，已經更新的數據怎么辦？難道我們要一個一個去找出來修改回來嗎？事務就是解決這種情況的，只有所有的數據更新正確才成功，如果有一條更新錯誤，那么所有的數據都回到解放前，變為沒有更新狀態。
來個demo更好理解吧
- FMDatabase使用事務
//事務
-(void)startTransaction {
// 開啟事務
[self.database beginTransaction];
BOOL isRollBack = NO;
@try {
for (int i = 0; i<100; i++) {
NSNumber *num = @(i+1);
NSString *name = [[NSString alloc] initWithFormat:@"student_%d",i];
NSString *sql = @"insert into mytable(num,name) values(?,?);";
BOOL result = [database executeUpdate:sql,num,name,sex];
if ( !result ) {
NSLog(@"插入失敗！");
return;
}
}
}
@catch (NSException *exception) {
isRollBack = YES;
// 事務回退
[self.database rollback];
}
@finally {
if (!isRollBack) {
//事務提交
[self.database commit];
}
}
}
- FMDatabaseQueue使用事務
//多線程事務
- (void)transactionByQueue {
//開啟事務
[self.queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
for (int i = 0; i<500; i++) {
NSNumber *num = @(i+1);
NSString *name = [[NSString alloc] initWithFormat:@"student_%d",i];
NSString *sex = (i%2==0)?@"f":@"m";
NSString *sql = @"insert into mytable(num,name,sex) values(?,?,?);";
BOOL result = [db executeUpdate:sql,num,name,sex];
if ( !result ) {
//當最后*rollback的值為YES的時候，事務回退，如果最后*rollback為NO，事務提交
*rollback = YES;
return;
}
}
}];
}
demo展示
@interface ViewController ()
@property (nonatomic, strong) FMDatabase *db;
@end
@implementation ViewController
@synthesize db;
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
// 1.獲得數據庫文件的路徑
NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filename = [doc stringByAppendingPathComponent:@"operDB.sqlite"];
// 2.得到數據庫
db = [FMDatabase databaseWithPath:filename];
}
- (IBAction)openDB:(id)sender {
// 3.打開數據庫
if ([db open]) {
NSLog(@"打開operDB成功");
}else {
NSLog(@"打開operDB失敗");
}
}
- (IBAction)createShopCarTable:(id)sender {
// 4.創表
if ([db open]) {
BOOL result = [db executeUpdate:@"CREATE TABLE IF NOT EXISTS shopCar (dbid integer PRIMARY KEY AUTOINCREMENT, specId integer NOT NULL, shopNum integer NOT NULL default 1, shopInfo TEXT NOT NULL);"];
if (result) {
NSLog(@"成功創表");
} else {
NSLog(@"創表失敗");
}
[db close];
}
}
- (IBAction)insertData:(id)sender {
if ([db open]) {
for (int i = 0; i < 5; i++) {
NSDictionary *dict = @{@"shopId":@(i+1),@"shopName":@"歐陽公仔",@"shopPrice":@(55.9 + i)};
NSString *shopInfo = [dict mj_JSONString];
NSString *insertSql1= [NSString stringWithFormat:@"INSERT INTO shopCar (specId, shopNum, shopInfo) VALUES (%d, %d, '%@')", i+2, i+3, shopInfo];
BOOL res = [db executeUpdate:insertSql1];
if (res) {
NSLog(@"數據插入表成功");
} else {
NSLog(@"數據插入表失敗");
}
}
[db close];
}
}
- (IBAction)selectAllData:(id)sender {
if ([db open]) {
NSString * sql = @"SELECT * FROM shopCar";
FMResultSet * rs = [db executeQuery:sql];
while ([rs next]) {
int dbId = [rs intForColumn:@"dbid"];
int specId = [rs intForColumn:@"specId"];
int shopNum = [rs intForColumn:@"shopNum"];
NSString * shopInfo = [rs stringForColumn:@"shopInfo"];
NSLog(@"dbId = %d, specId = %d, shopNum = %d shopInfo = %@", dbId, specId, shopNum, shopInfo);
}
[db close];
}
}
- (IBAction)selectDbidData:(id)sender {
if ([db open]) {
NSString * sql = @"SELECT * FROM shopCar WHERE dbid = '3'";
FMResultSet * rs = [db executeQuery:sql];
while ([rs next]) {
int dbId = [rs intForColumn:@"dbid"];
int specId = [rs intForColumn:@"specId"];
int shopNum = [rs intForColumn:@"shopNum"];
NSString * shopInfo = [rs stringForColumn:@"shopInfo"];
NSLog(@"dbId = %d, specId = %d, shopNum = %d shopInfo = %@", dbId, specId, shopNum, shopInfo);
}
[db close];
}
}
- (IBAction)updataDbidData:(id)sender {
if ([db open]) {
NSString *updateSql = [NSString stringWithFormat:@"update shopCar set shopNum = '88' where dbid ='3'"];
BOOL res = [db executeUpdate:updateSql];
if (res) {
NSLog(@"修改數據成功");
} else {
NSLog(@"修改數據失敗");
}
[db close];
}
}
- (IBAction)deleteDbidData:(id)sender {
if ([db open]) {
NSString *updateSql = [NSString stringWithFormat:@"DELETE FROM shopCar WHERE dbid = '3'"];
BOOL res = [db executeUpdate:updateSql];
if (res) {
NSLog(@"刪除指定數據成功");
} else {
NSLog(@"刪除指定數據失敗");
}
[db close];
}
}
- (IBAction)deleteAllData:(id)sender {
if ([db open]) {
//清空數據表并將自增字段清零
NSString *deleteSql = @"DELETE FROM shopCar";
[db executeUpdate:@"UPDATE sqlite_sequence set seq = 0 where name = 'shopCar'"];
BOOL res = [db executeUpdate:deleteSql];
if (res) {
NSLog(@"清空shopCar表數據成功");
} else {
NSLog(@"清空shopCar表數據失敗");
}
[db close];
}
}
- (IBAction)deleteShopCarTable:(id)sender {
if ([db open]) {
NSString *deleteSql = @"DROP TABLE shopCar";
BOOL res = [db executeUpdate:deleteSql];
if (res) {
NSLog(@"刪除shopCar表成功");
} else {
NSLog(@"刪除shopCar表失敗");
}
[db close];
}
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
