簡介:iOS開發的持久化數據存儲有4種方式:NSUserDefault和.plist、NSKeyedArchiver和NSKeyedUnarchiver、sqlite3數據庫、CoreData。
sqlite3和CoreData適合存儲大量數據(內容數據等),而另外兩種適合存儲簡單數據(語言,字體,標記等簡單數據存儲)。
準備:這里主要介紹利用sqlite3封裝的FMDatabase的數據庫,(當然還有PlausibleDatabase、sqlitepersistentobjects等其他封裝的庫),導入需要依賴的libsqlite3.dylib包,FMDatabase已經根據工程不同情況兼容ARC和非ARC。為了只針對數據庫進行講解,直接創建一個簡單工程,導入FMDatabase庫。
內容:1.創建數據庫
#import <UIKit/UIKit.h>#import "FMDatabase.h"#import "FMDatabaseQueue.h"@interface ViewController : UIViewController{ FMDatabase *db; FMDatabaseQueue *queue_db;}
//創建數據庫文件路徑- (NSString*)getPath{ NSArray* paths =NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES) ; return [[paths objectAtIndex:0]stringByAppendingPathComponent:@"TEST.sqlite"] ;}
2.數據庫的建表－增－刪－改操作
- (void)viewDidLoad { [super viewDidLoad]; [self executeSql:[self createTable]];//創表 [self executeSql:[self insertData]];//增 [self executeSql:[self deleteData]];//刪 [self executeSql:[self setData]];//改 //查 [self queryData]; //開辟多線程 [NSThread detachNewThreadSelector:@selector(multipleThread) toTarget:self withObject:nil]; }
//創建數據庫-(NSString *)createTable{ NSString *createSql = [NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS TEST(a interger,b text)"]; return createSql;}//增- (NSString *)insertData{ NSString *insertSql= [NSString stringWithFormat: @"INSERT INTO '%@' ('%@', '%@') VALUES ('%@', '%@')", @"TEST", @"a", @"b", [NSNumber numberWithInt:1], @"寧波"]; return insertSql;}//刪- (NSString *)deleteData{ NSString *deleteSql = [NSString stringWithFormat: @"DELETE FROM '%@' where %@ = '%@'", @"TEST", @"b", @"寧波"]; return deleteSql;}//改-(NSString *)setData{ NSString *setSql = [NSString stringWithFormat:@"UPDATE '%@' SET '%@' = '%@' WHERE '%@' = '%@'", @"TEST", @"b", @"象山" ,@"a", [NSNumber numberWithInt:1]]; return setSql;}
3.數據庫的執行操作
//數據庫執行操作-(BOOL)executeSql:(NSString *)sql{ db = [FMDatabase databaseWithPath:[self getPath]]; BOOL success; if ([db open]) { success = [db executeUpdate:sql]; }else{ NSLog(@"OPEN FAIL"); } [db close]; return success;}
4.數據庫的查詢操作
//查-(void)queryData{ if ([db open]) { NSString *querySql = [NSString stringWithFormat: @"SELECT * FROM %@",@"TEST"]; FMResultSet * rs = [db executeQuery:querySql]; while ([rs next]) { int a = [rs intForColumn:@"a"]; NSString *b = [rs stringForColumn:@"b"]; NSLog(@"a:%d == b:%@",a,b); } [db close]; }}
5.數據庫的多線程操作
若在多線程的環境下,不能在多線程中共用同一個FMDatabase進行數據訪問,會造成數據混亂,多線程下不能用單例對象,這時得依靠FMDatabaseQueue。
//多線程下使用FMDatabaseQueue進行數據庫操作-(void)multipleThread{ queue_db = [FMDatabaseQueue databaseQueueWithPath:[self getPath]]; @autoreleasepool{ [queue_db inDatabase:^(FMDatabase *db2) { [db2 executeUpdate:[self insertData]]; [self queryData]; }]; }}
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