Classes require various objects and parameters to function. The "Construct with Collaborators, Call with Work" guideline can help you construct effective inputs: 

• Use the constructor for collaborators—the dependencies that establish the object’s identity. Collaborators stay with the object for its lifetime to enable it to fulfill its ongoing duties.

• Pass work—the parameters that change with each interaction—to methods. Unique to each call, these inputs provide the specific data needed for an operation such as a file path or database query.

Consider a ReportGenerator that needs a database, a formatter, and a date range to generate a report. The database and formatter, as collaborators, are injected via the constructor, while dateRange, which varies per report generation, is passed as a method parameter to the generate method:

A single ReportGenerator object can generate multiple reports with different date ranges:

Following the "Construct with Collaborators, Call with Work" guideline promotes:

• Reusability: Enables instances to be used for multiple, distinct operations.

• Testability: Separates dependency setup from business logic.

• Cleaner code: Hides implementation dependencies from the object’s users.

• Predictable behavior: Locks in dependencies at creation time.

Note that the definition of "collaborator" versus "work" depends on the object's identity. For example, a RequestMessage could be a collaborator for a RequestHandler if the handler operates on a single request, or work if the handler processes different requests with each method call.