Applying a Qualifier

Like many other techniques in Managed Object Format (MOF), applying a qualifier to your code is a relatively simple process.

The only real challenges are the following restrictions in naming conventions that WMI enforces:

• A qualifier can describe a class, instance, property, method, or method parameter.

• Qualifier names cannot have either leading or trailing underscores.

• A qualifier name cannot begin with a digit.

• A qualifier name cannot contain special characters such as & * @ ! ~ \ /.

• All qualifier names are case-insensitive.

• You cannot redefine the standard WMI qualifiers or any qualifiers described in the DMTF CIM specification.

• Qualifier types are not explicitly declared.

  If you do not declare a qualifier type, WMI assumes the type as Boolean with a value of TRUE. Otherwise, WMI types qualifiers based on the qualifier values you declare.

• When creating your own qualifiers, you should prefix your schema name to your qualifier name.

  The purpose of this rule is to avoid confusion with new qualifiers.

• You can create homogeneous arrays of qualifiers.

  The following code example shows how qualifier arrays are specified with curly braces that surround the values.

  [StringArray{"hello", "there"}, SingleElementArray{3}]
  

• WMI does not support automation types not listed in the reference, such as VT_NULL. For more information, see MOF Data Types.

The following procedure helps you to use C++ to add a qualifier to a property.

To apply a qualifier using C++

• Apply the qualifier with a call to the IWbemQualifierSet::Put method.

  You can use other methods of IWbemQualifierSet to retrieve or delete existing qualifiers.

The following procedure helps you to apply a qualifier in MOF files.

To describe a keyword or identifier with a qualifier using MOF

• Place a qualifier in brackets before the keyword or identifier described by the qualifier.

  The following code example shows how qualifiers are used.

  [qualifiers...]
  class StdDisk
  {
    [qualifiers...]  uint32 dwNumCylinders;
    [qualifiers...]  uint32 dwNumHeads;
    [qualifiers...]  sint32 Method1();
    sint32 Method2([qualifiers...] Parameter1);
  };
  

  The following example describes the proper placement of qualifiers.

  [Abstract]
  class MyClass
  {
      [Amendment, InstanceOf]  uint32 dwNumber;
      sint32 MyMethod ([in] sint32 Param);
  };