RunnableFunction<RunInput extends Object, RunOutput extends Object> class

A RunnableFunction allows you to run a Dart function as part of a chain.

You can create a RunnableFunction using the Runnable.fromFunction static method.

When you call invoke on a RunnableFunction, it will invoke the function, passing the input to it. The output of the function is returned.

Example:

final openaiApiKey = Platform.environment['OPENAI_API_KEY'];
final model = ChatOpenAI(apiKey: openaiApiKey);

final promptTemplate = ChatPromptTemplate.fromTemplate(
  'How much is {a} + {b}?',
);

final chain = Runnable.fromMap({
      'a': Runnable.fromFunction((
        final Map<String, String> input,
        final options,
      ) async {
        final foo = input['foo'] ?? '';
        return '${foo.length}';
      }),
      'b': Runnable.fromFunction((
        final Map<String, String> input,
        final options,
      ) async {
        final foo = input['foo'] ?? '';
        final bar = input['bar'] ?? '';
        return '${bar.length * foo.length}';
      }),
    }) |
    promptTemplate |
    model |
    StringOutputParser();

final res = await chain.invoke({'foo': 'foo', 'bar': 'bar'});
print(res);
// 3 + 9 = 12