Defining the Greeter Interface in Slice

The first step of writing an Ice application is to define the contract between our client and server using Slice. For this example, we just want a single operation that accepts a name, and returns a greeting computed from this name. Let’s see how to express this in Slice.

Slice Files

All Slice definitions must be stored in Slice files, i.e. files ending with a .ice extension.
For this example, we write our definitions in a Slice file named Greeter.ice.

Writing the Greeter.ice Slice File

We start by adding a module to our Slice file. Modules are containers that can be used to organize Slice definitions into named groups. Slice requires that all definitions be contained within modules. So at this point, our Slice file looks like:

module VisitorCenter
{
    // ... definitions go here
}

Now that we have a module, there’s only one more thing we need before we can define our operation: an interface. Interfaces are at the core of Ice, as they specify the remote API (the ‘contract’) between clients and servers. So how you split your operations among interfaces can have large implications for the structure of your application. But, with only one operation, there’s no such considerations in this example:

    interface Greeter
    {
         // ... operations go here
    }

Finally, we can write our operation. It should take a name and return a greeting. So we write an operation named greet which takes a single string parameter (named name) and returns a string:

    string greet(string name);

Notice that there is no implementation for our operation. Slice is only for defining the API between clients and servers. How operations get called or implemented is not the domain of Slice, and will be covered separately in the following pages.

Putting it all together (and adding some doc-comments), here is what our final Slice file looks like:

module VisitorCenter
{
    /// Represents a simple greeter.
    interface Greeter
    {
        /// Creates a personalized greeting.
        /// @param name The name of the person to greet.
        /// @return The greeting.
        string greet(string name);
    }
}