The server-side mapping for interfaces provides an up-call API for the Ice run time: by implementing methods in a servant class, you provide the hook that gets the thread of control from the Ice server-side run time into your application code.
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Skeleton Classes in C#
On the client side, interfaces map to proxy classes. On the server side, interfaces map to skeleton classes. A skeleton is a class that has an abstract method for each operation on the corresponding interface. For example, consider our Slice definition for the Node interface:
module Filesystem {
interface Node {
idempotent string name();
};
// ...
};
The Slice compiler generates the following definition for this interface:
namespace Filesystem
{
public interface NodeOperations_
{
string name(Ice.Current __current);
}
public interface NodeOperationsNC_
{
string name();
}
public interface Node : Ice.Object, NodeOperations_, NodeOperationsNC_
{
}
public abstract class NodeDisp_ : Ice.ObjectImpl, Node
{
public string name()
{
return name(new Ice.Current());
}
public abstract string name(Ice.Current __current);
// Mapping-internal code here...
}
}
The important points to note here are:
- As for the client side, Slice modules are mapped to C# namespaces with the same name, so the skeleton class definitions are part of the
Filesystemnamespace. - For each Slice interface
<interface-name>, the compiler generates C# interfaces<interface-name>Operations_and<interface-name>OperationsNC_(NodeOperations_andNodeOperationsNC_in this example). These interfaces contain a method for each operation in the Slice interface. (You can ignore theIce.Currentparameter for the now.) - For each Slice interface
<interface-name>, the compiler generates a C# interface<interface-name>(Nodein this example). That interface extendsIce.Objectand the two operations interfaces. - For each Slice interface
<interface-name>, the compiler generates an abstract class<interface-name>Disp_(NodeDisp_in this example). This abstract class is the actual skeleton class; it is the base class from which you derive your servant class.
Servant Classes in C#
In order to provide an implementation for an Ice object, you must create a servant class that inherits from the corresponding skeleton class. For example, to create a servant for the Node interface, you could write:
public class NodeI : NodeDisp_
{
public NodeI(string name)
{
_name = name;
}
public override string name(Ice.Current current)
{
return _name;
}
private string _name;
}
By convention, servant classes have the name of their interface with an I-suffix, so the servant class for the Node interface is called NodeI. (This is a convention only: as far as the Ice run time is concerned, you can choose any name you prefer for your servant classes.) Note that NodeI extends NodeDisp_, that is, it derives from its skeleton class.
As far as Ice is concerned, the NodeI class must implement only a single method: the abstract name method that it inherits from its skeleton. This makes the servant class a concrete class that can be instantiated. You can add other methods and data members as you see fit to support your implementation. For example, in the preceding definition, we added a _name member and a constructor. (Obviously, the constructor initializes the _name member and the name method returns its value.)
Server-Side Normal and idempotent Operations in C#
Whether an operation is an ordinary operation or an idempotent operation has no influence on the way the operation is mapped. To illustrate this, consider the following interface:
interface Example {
void normalOp();
idempotent void idempotentOp();
};
The operations class for this interface looks like this:
public interface ExampleOperations_
{
void normalOp(Ice.Current __current);
void idempotentOp(Ice.Current __current);
}
Note that the signatures of the methods are unaffected by the idempotent qualifier.