如何在Python中設置一個空消息的ProtoBuf字段？

Question

以下是Google Protocol Buffer（.proto）文件的內容

message First
{
    required uint32 field1 = 1;

    optional MessageType1 request = 2;
}

message MessageType1
{
}

我想設置MessageType1字段請求。 但我認為這是一個錯誤：

AttributeError: Assignment not allowed to composite field "request" in protocol message object.

如何在Python中設置此空消息的值？

Answer 1

在Proto Buffer的Message類的源代碼中得到了這個。

  def SetInParent(self):
    """Mark this as present in the parent.

    This normally happens automatically when you assign a field of a
    sub-message, but sometimes you want to make the sub-message
    present while keeping it empty.  If you find yourself using this,
    you may want to reconsider your design."""

所以設置這樣一個空消息的方法是調用這個函數：

first.request.SetInParent()