按鈕按下時更新sql查詢？

Question

所以當我按下按鈕時，我想要做的是對我的sqlite數據庫運行UPDATE查詢。下面是我有和它不工作，我認爲的問題是，我打開數據庫從捆綁，這當然是只讀。現在我已經做了一些研究，並且意識到我應該：

1. 檢查Documents文件夾中是否存在數據庫。

2. 如果不存在，請將數據庫從數據包複製到Documents文件夾。

3. 現在，從Documents文件夾中打開數據庫。

但我不知道該怎麼做？任何幫助將不勝感激。這裏是我有什麼：

- (IBAction)update:(id)sender { 
@try { 
    NSFileManager *fileMgr = [NSFileManager defaultManager]; 
    NSString *dbPath = [[[NSBundle mainBundle] resourcePath ]stringByAppendingPathComponent:@"StayhealthyExercises-1.sqlite"]; 
    BOOL success = [fileMgr fileExistsAtPath:dbPath]; 
    if(!success) 
    { 
     NSLog(@"Cannot locate database file '%@'.", dbPath); 
    } 
    if(!(sqlite3_open([dbPath UTF8String], &db) == SQLITE_OK)) 
    { 
     NSLog(@"An error has occured: %s", sqlite3_errmsg(db)); 

    } 
    const char *sql = "UPDATE strengthexercises SET isFavorite = 'true' WHERE ID = '1'"; 
    sqlite3_stmt *sqlStatement; 
    if(sqlite3_prepare(db, sql, -1, &sqlStatement, NULL) != SQLITE_OK) 
    { 
     NSLog(@"Problem with prepare statement: %s", sqlite3_errmsg(db)); 
    }else{ 
     if (sqlite3_step(sqlStatement) == SQLITE_DONE){ 
      NSLog(@"Success"); 
     } 
    } 
    sqlite3_finalize(sqlStatement); 
} 
@catch (NSException *exception) { 
    NSLog(@"Problem with prepare statement: %s", sqlite3_errmsg(db)); 
} 
@finally { 
    sqlite3_close(db); 
} 

} 

一個明確的答案，一個例子會有很大的幫助。提前致謝。

更新＃1

現在我有這個，但它仍然沒有作用......

- (NSString *)applicationDocumentsDirectory { 
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil; 
return basePath; 
} 

- (IBAction)update:(id)sender { 
@try { 
    NSString *docsPath = [self applicationDocumentsDirectory]; 
    NSString *dbPath = [docsPath stringByAppendingPathComponent:@"StayhealthyExercises-1.sqlite"]; 
    BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:dbPath]; 
    if (!fileExists) { 
     // get the source path to copy from 
     NSString *dbSourcePath = [[[NSBundle mainBundle] resourcePath ]stringByAppendingPathComponent:@"StayhealthyExercises-1.sqlite"]; 
     // copy db to documents 
     [[NSFileManager defaultManager] copyItemAtPath:dbSourcePath toPath:dbPath error:nil]; 
    } 
    if(!(sqlite3_open([dbPath UTF8String], &db) == SQLITE_OK)) 
    { 
     NSLog(@"An error has occured: %s", sqlite3_errmsg(db)); 
    } 
    const char *sql = "UPDATE strengthexercises SET isFavorite = 'true' WHERE ID = '1'"; 
    sqlite3_stmt *sqlStatement; 
    if(sqlite3_prepare(db, sql, -1, &sqlStatement, NULL) != SQLITE_OK) 
    { 
     NSLog(@"Problem with prepare statement: %s", sqlite3_errmsg(db)); 
    }else{ 
     if (sqlite3_step(sqlStatement) == SQLITE_DONE){ 
      NSLog(@"Success"); 
     } 
    } 
    sqlite3_finalize(sqlStatement); 
} 
@catch (NSException *exception) { 
    NSLog(@"Problem with prepare statement: %s", sqlite3_errmsg(db)); 
} 
@finally { 
    sqlite3_close(db); 
} 

} 

Answer 1

寫回到這樣的文件路徑的方法 -

- (NSString *)applicationDocumentsDirectory { 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil; 
    return basePath; 
} 

然後檢查db是否存在於文檔路徑 -

NSString *docsPath = [self applicationDocumentsDirectory]; 
NSString *dbDocsPath = [docsPath stringByAppendingPathComponent:@"StayhealthyExercises-1.sqlite"]; 
BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:dbDocsPath]; 

使用條件，以確定是否需要DB複製，如果是複製 -

if (!fileExists) { 
    // get the source path to copy from 
    NSString *dbSourcePath = [[NSBundle mainBundle] pathForResource:@"StayhealthyExercises-1" ofType:@"sqlite"]; 
    // copy db to documents 
    [[NSFileManager defaultManager] copyItemAtPath:dbSourcePath toPath:dbDocsPath error:nil]; 
} 

您現在應該有你的數據庫的副本中，你可以讀/寫文件。