Question

-(NSMutableArray *)getStudentsInfo
{
    NSMutableArray *studentsList = [[NSMutableArray alloc]init];
    sqlite3_stmt* getStatement;

    const char* sql = "select * from Person";

    if (sqlite3_prepare_v2(database, sql, -1, &getStatement, NULL) != SQLITE_OK)
    {
        NSAssert1(0, @"Error: failed to prepare statement with message '%s'.", sqlite3_errmsg(database));
    }
    else{

        while (sqlite3_step(getStatement) == SQLITE_ROW)
        {
            Person* pObj = [[Person alloc]init];

            pObj.pNumber = sqlite3_column_int(getStatement,0);

            pObj.pName = [NSString stringWithUTF8String:(char*)sqlite3_column_text(getStatement, 1)];


            NSLog(@"Student Name is %@",pObj.pName);

            pObj.pRoundTime = [NSString stringWithUTF8String:(char*)sqlite3_column_text(getStatement, 2)];


            NSLog(@"Student Class is %@",pObj.pRoundTime);

            pObj.pRoundCount = [NSString stringWithUTF8String:(char*)sqlite3_column_text(getStatement, 3)];


            NSLog(@"Student Section is %@",pObj.pRoundCount);

            pObj.pRestTime = [NSString stringWithUTF8String:(char*)sqlite3_column_text(getStatement, 4)];


            NSLog(@"Student Section is %@",pObj.pRestTime);

             pObj.pAlertTime = [NSString stringWithUTF8String:(char*)sqlite3_column_text(getStatement, 5)];



             NSLog(@"Student Section is %@",pObj.pAlertTime);

             pObj.pPreparationTime = [NSString stringWithUTF8String:(char*)sqlite3_column_text(getStatement, 6)];



            NSLog(@"Student Section is %@",pObj.pPreparationTime);






            [studentsList addObject:pObj];
        }
        printf("Successfully retrieved data from database");

    }
    sqlite3_finalize(getStatement);

    return studentsList;

}

我在这里遇到一个问题，我存储的所有这些字段都存储为sqlite数据库中的浮点值，前两个字段除外。但是，当我想使用选择查询获取所有这些记录时，我不会获取并显示记录，并显示以下错误：

*由于未捕获的异常终止应用＆＃39; NSInvalidArgumentException＆＃39;，原因：＆＃39; * + [NSString stringWithUTF8String：]：NULL cString＆＃39;

Answer 1

将sqlite3_column_text替换为sqlite3_column_double以获取上述代码中的浮点值。

NSNumber *floatValue = [NSNumber numberWithFloat:(float)sqlite3_column_double(statement, column)];

以上是您可以申请获得浮动值的方法。

Answer 2

使用：

sqlite3_column_double(statement, column)

而不是：

sqlite3_column_text(statement, column)

如果是整数：

sqlite3_column_int(statement, column)

Answer 3

即使我使用double来获取浮点值，也会显示错误任何人都可以告诉我如何为这些下面的行写下正确的行

pObj.pRoundTime = [NSString stringWithUTF8String:(char*)sqlite3_column_text(getStatement, 2)];

如何获取存储在sqlite数据库中的浮点值？

3 个答案: