Client-Side MATLAB Mapping for Operations

Mapping for Operations

As we saw in the Client-Side MATLAB Mapping for Interfaces, for each operation on an interface, the generated proxy class contains 2 methods for this operation. To invoke an operation, you call one of these methods on the proxy. For example, let’s take the generated code from the greeter example:

["matlab:identifier:visitorcenter"]
module VisitorCenter
{
    interface Greeter
    {
        string greet(string name);
    }
}

The proxy class generated from the Greeter interface, after removing extra details, is as follows:

classdef GreeterPrx < Ice.ObjectPrx
    methods
        function returnValue = greet(obj, name, context)
            % ...
        end

        function future = greetAsync(obj, name, context)
            % ...
        end
    end
end

Given a proxy to an object of type Greeter, the client can invoke the greetoperation as follows:

greeter = visitorcenter.GreeterPrx(
    communicator, 'greeter:tcp -h localhost -p 4061');

greeting = greeter.greet('Alice');     % Get name via RPC

Sync and Async Methods

For each operation, the Slice compiler generates 2 methods on the proxy class:

• a “sync” method with the same name as the operation. When you call this method, your program waits synchronously until the invocation completes. A successful invocation completes with a return value (which can be void), while an unsuccessful invocation completes with an exception.

• an “async” method, named <operation-name>Async. When you call this method, your program marshals the arguments to the method synchronously, but the remainder of this invocation is asynchronous, and the method returns a future immediately. These async methods are described in more detail in Asynchronous Method Invocation (AMI) in MATLAB.

Async invocations allow you to perform other work while the server is processing the request. Sync invocations are more convenient to call. You decide what’s more important for your application.

Exception Handling

Any operation invocation may throw a runtime exception and, if the operation has an exception specification, may also throw user exceptions. Suppose we have the following simple interface:

exception Tantrum
{
    string reason;
}

interface Child
{
    void askToCleanUp() throws Tantrum;
}

Slice exceptions are thrown as MATLAB exceptions, so you can simply enclose one or more operation invocations in a try-catch block:

child = ...;   % Get child proxy...

try
    child.askToCleanUp();
catch ex
    if isa(ex, 'Tantrum')
        fprintf('The child says: %s\n', ex.reason);
    else
        rethrow(ex);
    end
end

See Also

• MATLAB Mapping for Parameters and Return Values

• Asynchronous Method Invocation (AMI) in MATLAB