iPhone：在分组 UITableview 的每个部分中重复行

Question

我正在尝试学习如何将 UITableView 与 SQLite 后端结合使用。我的问题是我已经得到了表格来填充数据库中的记录，但是我遇到了部分标题的问题。我无法为此找出正确的设置，并且我正在重复每个部分下的所有任务。

桌子看起来像这样。组字段是我试图从中提取部分标题的地方。

TaskID  groups      TaskName    sched   lastCompleted   nextCompleted   success
1       Household   laundry     3       03/19/2010      03/22/2010      y 
1       Automotive  Change oil  3       03/20/2010      03/23/2010      y 

在我的 viewDidLoad 方法中，我从表中的每一列创建一个数组，如下所示。

    //Create and initialize arrays from table columns
    //______________________________________________________________________________________

    ids =[[NSMutableArray alloc] init];
    tasks =[[NSMutableArray alloc] init];
    sched =[[NSMutableArray alloc] init];
    lastComplete =[[NSMutableArray alloc] init];
    nextComplete =[[NSMutableArray alloc] init];
    weight =[[NSMutableArray alloc] init];
    success =[[NSMutableArray alloc] init];
    group =[[NSMutableArray alloc] init];



// Bind them to the data
//______________________________________________________________________________________    
    NSString *query = [NSString stringWithFormat:@"SELECT * FROM Tasks ORDER BY nextComplete "];

    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2( database, [query UTF8String],
                           -1, &statement, nil) == SQLITE_OK) {
        while (sqlite3_step(statement) == SQLITE_ROW) {
            [ids addObject:[NSString stringWithFormat:@"%i",(int*) sqlite3_column_int(statement, 0)]];
            [group addObject:[NSString stringWithFormat:@"%s",(char*) sqlite3_column_text(statement, 1)]];
            [tasks addObject:[NSString stringWithFormat:@"%s",(char*) sqlite3_column_text(statement, 2)]];
            [sched addObject:[NSString stringWithFormat:@"%i",(int*) sqlite3_column_int(statement, 3)]];
            [lastComplete addObject:[NSString stringWithFormat:@"%s",(char*) sqlite3_column_text(statement, 4)]];
            [nextComplete addObject:[NSString stringWithFormat:@"%s",(char*) sqlite3_column_text(statement, 5)]];
            [success addObject:[NSString stringWithFormat:@"%s",(char*) sqlite3_column_text(statement, 6)]];
            [weight addObject:[NSString stringWithFormat:@"%i",(int*) sqlite3_column_int(statement, 7)]];




        }
        sqlite3_finalize(statement);
    }

在表格方法：cellForRowAtIndexPath 中，我动态创建控件并将它们的文本属性设置为数组中的对象。下面是一个示例，我可以提供更多，但我已经在这里写了一本书...... :)

/create the task label 
NSString *tmpMessage;
tmpMessage = [NSString stringWithFormat:@"%@ every %@ days, for %@ points",[tasks objectAtIndex:indexPath.row],[sched objectAtIndex:indexPath.row],[weight objectAtIndex:indexPath.row]];
    CGRect schedLabelRect = CGRectMake(0, 0, 250, 15);
    UILabel *lblSched = [[UILabel alloc] initWithFrame:schedLabelRect];
    lblSched.textAlignment = UITextAlignmentLeft;
    lblSched.text = tmpMessage;
    lblSched.font = [UIFont boldSystemFontOfSize:10];
    [cell.contentView addSubview: lblSched];
    [lblSched release];

我的 numberOfSectionsInTableView 方法看起来像这样

// Figure out how many sections there are by a distinct count of the groups field
// The groups are entered by user when creating tasks   
//______________________________________________________________________________________    
    NSString *groupquery = [NSString stringWithFormat:@"SELECT COUNT(DISTINCT groups) as Sum FROM Tasks"];
    int sum;

    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2( database, [groupquery UTF8String],
                           -1, &statement, nil) == SQLITE_OK) {
        while (sqlite3_step(statement) == SQLITE_ROW) {
            sum = sqlite3_column_int(statement, 0);

        }
        sqlite3_finalize(statement);
    }
    if (sum=0) {
        return 1;
    }
    return 2;
}

我知道我在这里出错了，但这就是我的 numberOfRowsInSection 方法中的全部内容

return [ids count];

Answer 1

从数据模型的角度来看，这就是您希望表格的样子：

"Household" section
    record 1 of (all records whose "group" column=="Household")
    record 2 of (all records whose "group" column=="Household")
    record 3 of (all records whose "group" column=="Household")
"Automotive" section
    record 1 of (all records whose "group" column=="Automotive")
    record 2 of (all records whose "group" column=="Automotive")
    record 3 of (all records whose "group" column=="Automotive")

因此，您的数据模型必须反映这种结构。现在，它没有。您只需将每一列加载到一个数组中，但数组之间没有关系，例如“组”数组中的每个元素与任何其他数组中的任何元素都没有关系。这意味着您无法将每个“组”与同一记录中的其他列相关联。

由于 SQL 没有结构，你必须提供一个对象层来将非结构化的 SQL 返回转换为结构化的。

（我的 SQL 生锈了，所以下面的所有 SQL 都是伪代码。）

// for simplicity, assume that the SQL table is indexed and always returns the same order
@property (nonAtomic,retain) NSArray *group;
@sythesize group;

- (void) viewWillAppear:(BOOL)animated{
    // here groups is the column with "Household", "Automotive" etc
    // You want them unique because you want all "Household" under the same section
    NSArray *unSortedgroup=SQL(every unique name in column "group");
    self.group=[unsortedSectionName arraySortedUsing...]; //Sort the array however you wish
}//------------------------------------viewWillAppear:------------------------------------

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return [self.group count];
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section{
    return [self.group objectAtIndex:section];  
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    NSString *sectionName=[self.group objectAtIndex:section];
    NSUInteger *rowCount=SQL(count of all records whose "group" column == sectionName);
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    //... setup cell


    NSString *sectionName=[self.group objectAtIndex:section];
    NSArray *rowsForThisSection=SQL(indexs of all records whose "group" column == sectionName);
    // the data for each row cell is now in/pointed to by [rowsForThisSection objectAtIndex:indexPath.row]
    cell.idLabel.text=SQL(column "id" of record whose index is [rowsForThisSection objectAtIndex:indexPath.row])

    // ... and so on for your other columns/attributes      
}

这就是创建 Core Data 的原因。 SQL 和其他串行形式必须硬塞到面向对象 API 使用的对象图中，这需要大量的胶水代码。使用 Core Data，您可以创建一个对象图，然后让后端担心它是如何存储到磁盘上的。

使用 Core Data，您可以用大约 8 行代码加上图形数据模型来完成所有这些工作。