NSOutlineView rowForItem：总是返回0

我有一个应用程序需要在某些列中异步更新单元格。我有一个GCD队列，其中添加了块，稍后获取使用-rowForItem:给出的行和列的单元格，但-rowForItem:的结果始终为0，并且每次都抛出NSAssert([self.outlineView itemAtRow:row] == item, @"rowForItem: and itemForRow: not reversible! (Item %@, row %ld)", item, (long)row);。我没有看到我在这里做错了什么。该索引不是-1，这意味着该项目未找到，但该项目被认为位于不正确的索引处。（第一项总是JODirectoryInfo，我只上JOFileInfo运行块，所以它不可能是错误的项目。）NSOutlineView rowForItem：总是返回0

- (NSTableCellView *)_cellForRow:(NSInteger)row columnIdentifier:(NSString *)column { 
    if (row < 0) return nil; 
    NSInteger colIdx = [self.outlineView columnWithIdentifier:column]; 
    if (colIdx == -1) return nil; 
    if (colIdx + 1 > self.outlineView.tableColumns.count) return nil; 
    return [self.outlineView viewAtColumn:colIdx row:row makeIfNecessary:NO]; 
} 
- (NSTableCellView *)_cellForItem:(id)item columnIdentifier:(NSString *)column { 
    NSInteger row = [self.outlineView rowForItem:item]; 
    NSAssert([self.outlineView itemAtRow:row] == item, @"rowForItem: and itemForRow: not reversible! (Item %@, row %ld)", item, (long)row); 
    DDLogVerbose(@"Getting cell for item %@ (row %ld) in column %@", item, (long)row, column); 
    return [self _cellForRow:row columnIdentifier:column]; 
} 

- (dispatch_block_t)_loadingBlockForItem:(JOFileInfo *)item block:(JOFileInfoBlock)block column:(NSString *)columnIdentifier { 
    return ^{ 
     NSTableCellView *cellView = [self _cellForItem:item columnIdentifier:columnIdentifier]; 
     if (!cellView) return; 
     cellView.objectValue = block(item); 
    }; 
} 
- (id)outlineView:(NSOutlineView *)outlineView objectValueForTableColumn:(NSTableColumn *)tableColumn byItem:(id)item { 
    DDLogVerbose(@"Requested value of column %@ for item %@", tableColumn.identifier, item); 
    if ([tableColumn.identifier isEqualToString:@"Size"]) { 
     if ([item isKindOfClass:[JOFileInfo class]]) { 
      dispatch_async(self.queue, [self _loadingBlockForItem:item block:^(JOFileInfo *item) { 
       unsigned long long size = item.size; 
       if (size != ULONG_LONG_MAX) return [self.byteCountFormatter stringFromByteCount:size]; 
       else return @"--"; 
      } column:tableColumn.identifier]); 
      return @"--"; 
     } else { 
      return @"--"; 
     } 
    } else { 
     return @"text"; 
    } 
}

来源

2013-06-28 Josh The Geek

它返回零，因为大纲视图为零。

来源

2013-07-06 15:48:09

NSOutlineView rowForItem：总是返回0

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