How to register a service to trigger a method and override it

Need to register a service to trigger a method but override it in the class I'm working on

The service forces dirty objects to save with a custom function.

The class needs to use the service to activate the function.

Tried the following code:

operationManager:service()&

operationManager:service('operation-manager')

in init

this.register(this.get('operationManager'));

and override method in class

forcePendingSave: function(){console.log('need to get here')}

The service is not initting therefore not registering properly.