kann keine Datenbanktabelle erstellen und in iOS einfügen sqlite3

Question

Ich bin neu in iOS-Entwicklung. Ich versuche eine einfache Todo-Liste App zu machen. Ich benutze Xocde 8 und Ziel-C-Sprache. Ich habe mehrere Tutorials ausprobiert, konnte aber die Datenbanktabelle nicht erstellen. Hier ist mein Code.

-(void)createOrOpenDB{ 
    printf("createOrOpenDB: into this function \n"); 

    NSArray *docsDir = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *dirPaths = [docsDir objectAtIndex:0]; 

    dbPathString = [[NSString alloc] initWithString: [dirPaths stringByAppendingPathComponent:@"person.db"]]; 

    NSFileManager *fileManager = [NSFileManager defaultManager]; 

    char *err; 
    printf("createOrOpenDB: into this function before if statement \n"); 
    if(![fileManager fileExistsAtPath:dbPathString]){ 
     const char *dbPath = [dbPathString UTF8String]; 
      printf("createOrOpenDB: into this functions 1st if statement \n"); 
     //create db here 
     if(sqlite3_open(dbPath, &personDB) ==SQLITE_OK){ 
      const char *sql_stnt = "CREATE TABLE IF NOT EXISTS PERSONS (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, AGE INTEGER)"; 
      if(sqlite3_exec(personDB, sql_stnt, NULL, NULL, &err) !=SQLITE_OK){ 
       printf("Failed to create table\n"); 
      } 
      sqlite3_close(personDB); 
      printf("createOrOpenDB: database table created\n"); 
     } 
    } 
} 

, wenn ich die Add-Taste drücken, das gibt mir keine Fehler. aber es fügt keine Daten hinzu. NSLog in xcode 8 nicht funktioniert. also habe ich stattdessen printf gemacht. und mein Code bricht vor der if-Anweisung. kann mir jemand sagen, was ich falsch mache?

Answer 1

wie dies tun,

+(DBManager*)getSharedInstance{ 
    if (!sharedInstance) { 
     sharedInstance = [[super allocWithZone:NULL]init]; 
     [sharedInstance createDB]; 
    } 
    return sharedInstance; 
} 

-(BOOL)createDB{ 
    NSString *docsDir; 
    NSArray *dirPaths; 
    // Get the documents directory 
    dirPaths = NSSearchPathForDirectoriesInDomains 
    (NSDocumentDirectory, NSUserDomainMask, YES); 
    docsDir = dirPaths[0]; 
    // Build the path to the database file 
    databasePath = [[NSString alloc] initWithString: 
        [docsDir stringByAppendingPathComponent: @"student.db"]]; 
    BOOL isSuccess = YES; 
    NSFileManager *filemgr = [NSFileManager defaultManager]; 
    if ([filemgr fileExistsAtPath: databasePath ] == YES) 
    { 
     const char *dbpath = [databasePath UTF8String]; 
     if (sqlite3_open(dbpath, &database) == SQLITE_OK) 
     { 
      char *errMsg; 
      const char *sql_stmt = "create table if not exists studentsDetail (regno integer primary key, name text, department text, year text)"; 
      if (sqlite3_exec(database, sql_stmt, NULL, NULL, &errMsg) 
       != SQLITE_OK) 
      { 
       isSuccess = NO; 
       NSLog(@"Failed to create table"); 
      } 
      else 
      { 
       NSLog(@"Table Created Successfully"); 
      } 
      sqlite3_close(database); 
      return isSuccess; 
     } 
     else { 
      isSuccess = NO; 
      NSLog(@"Failed to open/create database"); 
     } 
     sqlite3_finalize(statement); 
    } 
    return isSuccess; 
    // NSLog(@"database %@", isSuccess); 
} 

Für in dieser Tabelle die Daten zu speichern,

- (BOOL) saveData:(NSString*)registerNumber name:(NSString*)name 
     department:(NSString*)department year:(NSString*)year; 
{ 
    const char *dbpath = [databasePath UTF8String]; 
    if (sqlite3_open(dbpath, &database) == SQLITE_OK) 
    { 
     NSString *insertSQL = [NSString stringWithFormat:@"insert into studentsDetail (regno,name, department, year) values (\"%ld\",\"%@\", \"%@\", \"%@\")",(long)[registerNumber integerValue], name, department, year]; 
           const char *insert_stmt = [insertSQL UTF8String]; 
           sqlite3_prepare_v2(database, insert_stmt,-1, &statement, NULL); 
           if (sqlite3_step(statement) == SQLITE_DONE) 
           { 
            return YES; 
           } 
           else { 
            return NO; 
           } 
           sqlite3_reset(statement); 
           } 
           return NO; 
           } 

Es wird jedes Mal erstellen Tabelle, wenn Tabelle nicht existiert.

Hoffnung t hilft dir.