Exposing Methods

 

Methods are implemented as functions or subroutines in your Windows Script Component file.

Procedures

To expose a method

1. Create a <public> element as a child of the <component> element.

2. In the <public> element, include a <method> element. The method element can optionally include one or more <parameter> elements to define the method's parameters.

3. Write a procedure in any scripting language to implement the function. Place the procedure in a <script> element outside the <implements> element but within the <component> element. Be sure the function name matches the functionName, or if you did not specify a functionName, the methodName name you specified in the <method> element.

   For example, the following example shows a fragment from a script component file with two methods, factorial and getRandomNumber.

   Note

   A CDATA section is required to make the script in the <script> element opaque. For details, see Script Component Files and XML Conformance.

   <public>
      <method name="factorial"/>
      <method name="random" internalName="getRandomNumber">
         <parameter name="upperBound"/><parameter name="seed"/>
      </method>
   </public>
   
   <script language="VBScript">
   Function factorial(n)
      <![CDATA[
      If isNumeric(n) Then
         If n <= 1 Then
            factorial = 1
         Else
            factorial = n*factorial(n-1)
         End If
      Else
         factorial = -2   ' Error code.
      End If
   End Function
   
   Function getRandomNumber(upperBound, seed)
      getRandomNumber = Cint(upperBound * Rnd(seed) + 1)
   End Function
   ]]>
   </script>
   

You can specify a default method for a script component so the host application can invoke the method without explicitly calling it. For example, if you have exposed a method called factorial and marked it as the default, you can call it in the following ways in Visual Basic:

Set component = CreateObject("component.MyComponent")
n = component.factorial(4)   ' Calls factorial method explicitly.
n = component(4)   ' Calls factorial method as default.

To specify a default method, include an attribute assigning a special dispatch identifier (a dispid) to the method. For more information about dispids, see Exposing Events.

To specify a default method

1. In the <method> element, include the attribute dispid="0", as shown in the following example:

   <public>
      <method name="factorial" dispid="0"/>
   </public>
   

   Note

   This technique can be used to assign either a default method or a default property, but not both. There can be only one element in the script component with the dispid of zero.

See Also

Exposing Events
Exposing Properties
Script Component File Contents