数据库通信

Question

我正在处理sqlite数据库从一个视图控制器到另一个视图控制器之间的通信，但是一些我无法在第二个视图控制器上获得数据库的方法。贝娄是我正在使用的代码。

论第一视图控制器

    //Creating a table of MOtivational Thoughts
    dirPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    docsDir = [dirPath objectAtIndex:0];
    Second.databasePath = [[NSString alloc]initWithString:[docsDir stringByAppendingPathComponent:@"S.H.E.D_DB"]];
    NSFileManager *filemgr = [NSFileManager defaultManager];
    if ([ filemgr fileExistsAtPath: Second.databasePath] == NO) {
        const char *dbpath = [Second.databasePath UTF8String];
        if (sqlite3_open(dbpath, &contactDB) == SQLITE_OK)
        {
            char *errMsg;
            const char *sql_stmt =
            "CREATE TABLE IF NOT EXISTS THOUGHTS (ID integer ,Motivation_Thaought TEXT)";

            if (sqlite3_exec(contactDB, sql_stmt, NULL, NULL, &errMsg) != SQLITE_OK)
            {
               NSLog(@"Failed to create table");
            }
            else
            {
                NSLog(@" created table");
            }
            sqlite3_close(contactDB);
        } else {


        }
    }

   // Fetching Data from table of MOtivational Thoughts 
   if(sqlite3_open([Second.databasePath UTF8String], &contactDB) == SQLITE_OK) {
    // Setup the SQL Statement and compile it for faster access

        int randomNumber = [self getRandomNumberBetween:0 to:6];

        NSString *queryString = [NSString stringWithFormat:@"Select * FROM THOUGHTS where ID= '%d'",randomNumber];
        const char* sql = [queryString UTF8String];
        NSLog(@"path value : %@", Second.databasePath);
        sqlite3_stmt *compiledStatement;

         if (sqlite3_prepare_v2(contactDB, sql, -1, &compiledStatement, nil)==SQLITE_OK)      {
            // Loop through the results and add them to the feeds array
            NSLog(@"Ready to enter while loop");

            while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
                // Read the data from the result row
                NSLog(@"reading");
                NSString *aid = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)];
                motivationView.text = aid;
                NSLog(@"Thought of the day %@", aid);

            }
        }
        // Release the compiled statement from memory
        sqlite3_finalize(compiledStatement);

    }
    sqlite3_close(contactDB);
       // Do any additional setup after loading the view from its nib.
    }

第二视图控制器研究

 NSLog(@"path value : %@", databasePath);
    if(sqlite3_open([databasePath UTF8String], &contactDB) == SQLITE_OK){
        char *errMsg;
        const char *sql_stmt =
        "CREATE TABLE IF NOT EXISTS SHEDSLIST (SHED_ID integer ,SHED_Name TEXT ,SHED_Description TEXT, SHED_TIME DATETIME)";

        if (sqlite3_exec(contactDB, sql_stmt, NULL, NULL, &errMsg) != SQLITE_OK)
        {
            NSLog(@"Failed to create table");
        }
        else
        {
            NSLog(@" created table");
       }
        sqlite3_close(contactDB);
    } else {


    }

PLease定位我的错误并给我一个合适的解决方案。

Answer 1

也许您应该以self.databasePath的形式在SecondViewController中访问数据库路径，因为我相信您已经为此创建了一个属性。相反，您正在尝试访问某些实例变量databasePath。查看FirstViewController中的以下代码：

Second.databasePath = [[NSString alloc]initWithString:[docsDir stringByAppendingPathComponent:@"S.H.E.D_DB"]];