Question

我是iOS开发的新手。我正在尝试做一个简单的待办事项列表应用程序。我正在使用xocde 8和Objective-C语言。我尝试了几个教程，但无法创建数据库表。这是我的代码。

-(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");
        }
    }
}

当我按下添加按钮时，它没有给我任何错误。但它没有添加任何数据。 NSLog不在xcode 8中工作。所以我做了printf而不是。我的代码在if语句之前中断。谁能告诉我我做错了什么？

Answer 1

这样做，

@Html.TextBoxFor(model => model.PlayerId, htmlAttributes: new { @readonly = "read-only", @class = "control-label col-md-2", Value = @Html.Raw(TempData["PlayerID"]) })

对于在此表中保存数据，

+(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);
}

每当表不存在时，它将创建表。

希望对你有帮助。

无法在iOS sqlite3中创建数据库表并插入

1 个答案: