Question

The Delphi 2009 XML Data Binding Wizard fails to process a simple XSD which contains a complexContent declaration (Invalid Pointer Operation).

Is it a bug or a know limitation?

Example:

<?xml version="1.0" encoding="utf-8"?>
<xsd:schema targetNamespace="http://example.org/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    elementFormDefault="qualified">

  <xsd:complexType name="TestType">
    <xsd:complexContent>
      <xsd:restriction base="xsd:anyType">
        <xsd:attribute name="Name" type="xsd:string"/>
      </xsd:restriction>
    </xsd:complexContent>
  </xsd:complexType>

</xsd:schema>

Edit: other examples work fine, so it looks like a part of the complexContent definition causes the error. Working example:

<xsd:complexType name="pc-Typ">
  <xsd:sequence>
    <xsd:element name="name"       type="xsd:string"/>
  </xsd:sequence>
  <xsd:attribute name="id" type="xsd:integer"/>
</xsd:complexType>

<xsd:complexType name="myPC-Typ">
  <xsd:complexContent>
    <xsd:extension base="pc-Typ">
      <xsd:sequence>
        <xsd:element name="ram" type="xsd:integer"/>
      </xsd:sequence>
    </xsd:extension>
  </xsd:complexContent>
</xsd:complexType>

Answer 1

Can I use xsd:complexContent with the Delphi XML Binding Wizard?

Yes, xsd:complexContent can be used.

I know Delphi has its flaws, but I don’t blame Delphi for this schema. XSD is a rich schema language, and so is Delphi’s OO class. Parts of two worlds overlap, but there are parts that won’t. XML databinding is an act of translating an XML schema into OO class structure, so the schema has to be concrete enough to be expressed as class.

In this example, you are saying that TestType matches any type so long as it has a string attribute called Name. An XML validator may be ok with that kind of definition, but it’s hard to define that in a single-inheritance model, since foo:Animal, foo:Plant, and foo:Mineral may all have Name attribute.

I defined an empty complexType called TestBaseType and that generated class perfectly fine.

<?xml version="1.0" encoding="utf-8"?>
<xsd:schema targetNamespace="http://example.org/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    elementFormDefault="qualified">

  <xsd:complexType name="TestBaseType">
    <xsd:sequence>
    </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name="TestType">
    <xsd:complexContent>
      <xsd:restriction base="TestBaseType">
        <xsd:attribute name="Name" type="xsd:string"/>
      </xsd:restriction>
    </xsd:complexContent>
  </xsd:complexType>
</xsd:schema>

This generated the following code:

unit test;

interface

uses xmldom, XMLDoc, XMLIntf;

type

{ Forward Decls }

  IXMLTestBaseType = interface;
  IXMLTestType = interface;

{ IXMLTestBaseType }

  IXMLTestBaseType = interface(IXMLNode)
    ['{0FBC1D84-DA5E-4315-83A9-B5FFE9528969}']
  end;

{ IXMLTestType }

  IXMLTestType = interface(IXMLTestBaseType)
    ['{12E35067-516F-4457-8C62-4131CA60D706}']
    { Property Accessors }
    function Get_Name: WideString;
    procedure Set_Name(Value: WideString);
    { Methods & Properties }
    property Name: WideString read Get_Name write Set_Name;
  end;

{ Forward Decls }

  TXMLTestBaseType = class;
  TXMLTestType = class;

{ TXMLTestBaseType }

  TXMLTestBaseType = class(TXMLNode, IXMLTestBaseType)
  protected
    { IXMLTestBaseType }
  end;

{ TXMLTestType }

  TXMLTestType = class(TXMLTestBaseType, IXMLTestType)
  protected
    { IXMLTestType }
    function Get_Name: WideString;
    procedure Set_Name(Value: WideString);
  end;

implementation

{ TXMLTestBaseType }

{ TXMLTestType }

function TXMLTestType.Get_Name: WideString;
begin
  Result := AttributeNodes['Name'].Text;
end;

procedure TXMLTestType.Set_Name(Value: WideString);
begin
  SetAttribute('Name', Value);
end;

end.