如何查找「NSTableColumn」的關鍵字來繪製排序指示符？

Question

我創建了一個自定義NSTableViewHeader。一切工作正常，但我沒有找到一個簡單的方法來獲取當前列的「關鍵」，以檢查是否應該繪製排序指標。

這裏的核心代碼檢查排序指標：

// Check if we need to draw a sort descriptor 
for (NSInteger priority = 0; priority < self.tableView.sortDescriptors.count; ++priority) { 
    NSSortDescriptor *sortDesciptor = self.tableView.sortDescriptors[priority]; 
    if ([sortDesciptor.key isEqualTo:???????]) { 
     [tableHeaderCell drawSortIndicatorWithFrame:rect inView:self ascending:sortDesciptor.ascending priority:priority]; 
    } 
} 

要了解來龍去脈，這裏的整個drawRect代碼：

- (void)drawRect:(NSRect)dirtyRect 
{ 
    [NSGraphicsContext saveGraphicsState]; 
    // Fill the background 
    [_backgroundColor setFill]; 
    const CGRect headerRect = CGRectMake(0.0, 1.0, self.bounds.size.width, self.bounds.size.height-1.0); 
    [[NSBezierPath bezierPathWithRect:headerRect] fill]; 

    // Draw separators and column header text. 
    for (NSUInteger i = 0; i < self.tableView.numberOfColumns; ++i) { 
     NSRect rect = [self headerRectOfColumn:i]; 
     if (i != 0) { 
      [[NSColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.35] setFill]; 
      [[NSBezierPath bezierPathWithRect:NSMakeRect(rect.origin.x, rect.origin.y+4.0, 1.0, rect.size.height-8.0)] fill]; 
     } 
     NSTableColumn *tableColumn = self.tableView.tableColumns[i]; 
     NSTableHeaderCell *tableHeaderCell = tableColumn.headerCell; 
     NSString *columnText = tableHeaderCell.stringValue; 
     [columnText drawInRect:NSInsetRect(rect, 5.0, 4.0) withAttributes:_headerTextAttributes]; 

     // Check if we need to draw a sort indicator 
     for (NSInteger priority = 0; priority < self.tableView.sortDescriptors.count; ++priority) { 
      NSSortDescriptor *sortDesciptor = self.tableView.sortDescriptors[priority]; 
      if ([sortDesciptor.key isEqualTo:tableColumn.key]) { 
       [tableHeaderCell drawSortIndicatorWithFrame:rect inView:self ascending:sortDesciptor.ascending priority:priority]; 
      } 
     } 
    } 
    [NSGraphicsContext restoreGraphicsState]; 
} 

我如何才能找到「鑰匙」了當前列檢查是否應繪製排序指示符？

Answer 1

我工作的唯一方法是檢查NSTableColumn的綁定。這對我很有用，因爲我使用了NSArrayController。我的NSTableView正在使用基於單元格的佈局，並且每個NSTableColumn都綁定到arrangedObjects.xxx關鍵路徑。

// Check if we need to draw a sort descriptor 
for (NSInteger priority = 0; priority < self.tableView.sortDescriptors.count; ++priority) { 
    NSSortDescriptor *sortDesciptor = self.tableView.sortDescriptors[priority]; 
    NSDictionary *bindingInfo = [tableColumn infoForBinding:@"value"]; 
    NSString *keyPath = bindingInfo[NSObservedKeyPathKey]; 
    keyPath = [keyPath stringByReplacingOccurrencesOfString:@"arrangedObjects." withString:@""]; 
    if ([sortDesciptor.key isEqualTo:keyPath]) { 
     [tableHeaderCell drawSortIndicatorWithFrame:rect inView:self ascending:sortDesciptor.ascending priority:priority]; 
    } 
} 

但是這不適用於基於視圖的表。這真的是唯一的解決方案嗎？