Question

我想将this example转换为Delphi代码，我的问题在于获得“Associators of”语句查询的结果：

procedure TUSB.GetInfo;
var
 WMIService : OLEVariant;
 DItems, PItems, LItems, VItems: OLEVariant;
 Drive, Partition, Logical, Volume : OLEVariant;
 Drives, Partitions, Logicals, Volumes : IEnumVARIANT;
 IValue : LongWord;
begin
 WMIService := GetWMIObject('winmgmts:\\localhost\root\cimv2');
 DItems := WMIService.ExecQuery('select DeviceID, Model from Win32_DiskDrive where InterfaceType='+QuotedStr('USB'));

 Drives := IUnKnown(DItems._NewEnum) as IEnumVARIANT;
 Drives.Next(1, Drive, IValue);
 DeviceID := Drive.Properties_.Item('DeviceID', 0);

 PItems := WMIService.ExecQuery('associators of {{Win32_DiskDrive.DeviceID='+QuotedStr(DeviceID)+'}} where AssocClass = Win32_DiskDriveToDiskPartition');

 Partitions := IUnKnown(PItems._NewEnum) as IEnumVARIANT;
 Partitions.Next(1, Partition, IValue);
 **PDeviceID := Partition.Properties_.Item('DeviceID', 0);**

...

end;

在标有2星的行中！我收到错误：“ 无效的变体操作 ”，而在上面的相同代码中，不是任何错误！

问题是什么？，在“协会的声明”或......？！

非常感谢...

Answer 1

如果没有看到所有相关的代码和声明，很难说清楚当你写：

Partitions.Next(1, Partition, IValue);

你应该在Partition检查你是否真正得到了你想要的东西更一般地说，要进行调试，您应该始终打破复合语句来测试每个中间步骤：

Partition.Properties_  // is it correct? how many items?
Partition.Properties_.Item('DeviceID', 0) // if not OK try to iterate through all items

Answer 2

感谢弗朗索瓦......

“没有看到所有人就很难说出来相关的代码和声明。“

但是没有更相关的代码！，我更改了以下代码：

procedure TUSBItem.GetInfo;
var
 WMIService : OLEVariant;
 DItems, PItems, LItems, VItems: OLEVariant;
 Drive, Partition, Logical, Volume : OLEVariant;
 Drives, Partitions, Logicals, Volumes : IEnumVARIANT;
 IValue : LongWord;
begin
 WMIService := GetWMIObject('winmgmts:\\localhost\root\cimv2');

 DItems := WMIService.ExecQuery('select DeviceID, Model from Win32_DiskDrive where InterfaceType='+QuotedStr('USB'));
 Drives := IUnKnown(DItems._NewEnum) as IEnumVARIANT;
 while Drives.Next(1, Drive, IValue) = S_OK do
  begin
   DeviceID := Drive.Properties_.Item('DeviceID', 0);
   PItems := WMIService.ExecQuery('associators of {{Win32_DiskDrive.DeviceID='+QuotedStr(DeviceID)+'}} where AssocClass = Win32_DiskDriveToDiskPartition');
   Partitions := IUnKnown(PItems._NewEnum) as IEnumVARIANT;
   if Partitions.Next(1, Partition, IValue) = S_OK then
    begin
     if not VarIsNull(Partition) then
      PDeviceID := Partition.Properties_.Item('DeviceID', 0);
    end;
   ...
  end;
 ...
end;

在 While 循环中，对于驱动器Enumerate Variant中的每个驱动器，我得到一个“DeviceID”，我应该将“DeviceID”传递给“Associators of”语句以获取与之关联的分区列表作为查询结果由“DeviceID”驱动...

在下一行中，我将分区中的PItems作为IEnumVARIANT，接下来我检查分区中的第一个分区元素是否返回“S_OK”（成功！）然后我检查分区，如果它不是t null then i get one of it s项名为“DeviceID”，但在此行中我收到此消息的错误：“无效的变体操作”

有相同的方法来获取驱动器的DeviceID和分区的DeviceID，但是当我想获得分区的DeviceID时我得到了一个错误，它们和它的WMI查询之间有一个不同，我猜问题是但是我不确定！

有一些有用的句子：

“但是，在编写框架提供程序时，请记住以下几点：

* Make sure you support standard queries in your association class, especially queries where the reference properties are used in a WHERE clause. For more information, see CFrameworkQuery::GetValuesForProp.
* In your association class support, when you check to see if the endpoints exist, ensure you use the CWbemProviderGlue::GetInstanceKeysByPath or CWbemProviderGlue::GetInstancePropertiesByPath methods.

  These methods allow the endpoints to skip populating expensive or unneeded properties.
* Make sure any association endpoint classes support per-property Get methods. For more information, see Supporting Partial-Instance Operations. For more information about the query parameter, see CFrameworkQuery. **"**

因为这个解释！，我认为问题是路径！，意味着我应该将我的目标（这里是分区）提供给WMIService对象以获得结果！，there is some help它，但我完全糊涂了!!!!

当然在转换它的Source page中，不是关于路径的任何解释......！

非常感谢...

在WMI查询中获取“关联者”结果的问题（无效的变体操作！）

2 个答案: