Command-Query Responsibility Segregation, or CSRQ, provides the ability to separate Query from Commands responsibilities using SOLID Principles. Queries retrieve information from a sink (data store) for the user. A command performs a task, such as update a sink (data store). Commands mutate state, while a Query does not. Technically, a Command does not return a value; however, the example which follows will return status. Each provides a single responsibility (Single Responsibility principle in Solid).

Documentation can be found in the docs directory and CQRS

The sample code is just that. There is room for much improvement and robustness. The Unit Tests are enough to provide at least 75% code coverage. If one decides to use the code, it is AS-IS. Finally, the code was prefixed with either cqrs_ or util_ to avoid name collision. The packaging does not use a namespace but was tested and can be packaged as a 2GP unlocked package.

The simplest thing to do is start with a sample command. This example is found in the source tree (./scripts/apex/exampleCommand.apex). Please note this is a raw form and can be used in a service supporting specific functionality (i.e., Customer Management, Lead Management, etc.). Above, is a collection of commands, creates a Command Dispatcher, passes in the command collection, and the dispatcher finds the appropriate handlers and executes.

// list of commands to run (default behavior is to exits on bad status on any command)
final List<cqrs_ICommand> commands = new List<cqrs_ICommand> {
    new cqrs_AuthenticationCommand('test-uid','test-password'),
    new cqrs_WriteResultCommand('test-id')
};
cqrs_ICommandResult result= new cqrs_CommandDispatcher().dispatch(commands);
System.debug('++++++++++++++++RESULTs++++++++++++++++++++++++++++');
System.debug('Command(s) Result Successful?:' + result.success());
System.debug('Command(s) Result:' + result);

Like the sample command there is a sample query. This example is found in the source tree (./scripts/apex/exampleQuery.apex). Please note, this too is a raw form and can be used in a service supporting specific functionality (i.e., Customer Management, Lead Management, etc.)

// set up / arrange
final List<cqrs_IQuery> queries = new List<cqrs_IQuery> {
   // get account by type ()
   new cqrs_GetAccountByTypeQuery('Enterprise')
};
Integer inx=1;
// act -- dispatcher looks up a handler and executes
final cqrs_IQueryResult result= new cqrs_QueryDispatcher().dispatch(queries);
//
// results
//
System.debug('++++++++++++++++RESULTs++++++++++++++++++++++++++++');
System.debug('Query(s) Result Successful ?:' + result.success());
System.debug('Query(s) Result Count Found :' + result.results().size());
System.debug('Query(s) Result Searched for: "' + ((cqrs_GetAccountByTypeQuery)queries[0]).theUserAccountType() + '"' );
System.debug('++++++++++++++++RECORDs++++++++++++++++++++++++++++');
//
// iterate over the results
for ( cqrs_AccountTypeRecordsDTO dto: (List<cqrs_AccountTypeRecordsDTO>)result.results() ) {
   System.debug('Query Result (' + inx++ + ') Name=' + dto.name);
}

Following the same flow as a command, the above is a collection of (one) query, where we create a Query Dispatcher, pass in the query collection, and the dispatcher finds the appropriate handlers and executes.

The Commands and Queries can be used to form a Service. The service could be Customer Search, Customer Management, Order Management, etc. In this example, we create a Customer Service. The Customer Service just contains a query method; it could contain a sundry of services relevant to Customer Service.

//
// Call a Service directly -- service wraps Command and Query Behavior
//
Integer inx=1;
// The Service Name -- Note, it looks for the service based on name and running environment
// If run from anonymous window ( that is considered "Debug" mode
//
final String serviceName='Customer Service';
// our account type parameter
final String accountType = 'enterprise';
//
// get the service by name -- resolver looks for service by name and runtime environment ( this can be overloaded)
cqrs_CustomerService service = (cqrs_CustomerService) cqrs_ServiceProvider.newInstance().getService( serviceName);
//
// show some service information
System.debug('++++++++++++++++RESULTs++++++++++++++++++++++++++++');
System.debug('Service Name:' + service.name());
System.debug('Service Guid:' + service.guid());
System.debug('++++++++++++++++RECORDs++++++++++++++++++++++++++++');
//
// iterate over the results (DTO)
//
for ( cqrs_AccountTypeRecordsDTO dto: service.findAccountRecordsByAccountType(accountType)) {
  System.debug('Service Result (' + inx++ + ') Name=' + dto.name);
}

The above Customer Service, cqrs_CustomerService, uses a provider to return the service by name. The service holds similar attributes of a Command or Query (name, guid, user-context). Our service method, findAccountRecordsByAccountType(accountType) passes in an account type, value of enterprise, and gets back a collection (Data Transfer Object) of Account Type Records.

Download the directory. Assumes you have :

• SFDX installed
• Dev Hub,
• Bash or Git-Bash

you can install this offering by running the following script from the source root directory:

./scripts/inint/install.sh -v YOUR-DEV-HUB -l <#-of-days-the-Scratch-Org-Is-Active>

for example:

./scripts/inint/install.sh -v MyDevHub -l 5

Note, some work was done on a Windows (git-bash), script may have carriage-control, line-feed causing issues in a Unix (Mac) environment