Question

I have question regarding the use of function parameters.

In the past I have always written my code such that all information needed by a function is passed in as a parameter. I.e. global parameters are not used.

However through looking over other peoples code, functions without parameters seem to be the norm. I should note that these are for private functions of a class and that the values that would have been passed in as paramaters are in fact private member variables for that class.

This leads to neater looking code and im starting to lean towards this for private functions but would like other peoples views.

E.g.

Start();  
Process();  
Stop();  

is neater and more readable than:

ParamD = Start(paramA, ParamB, ParamC);  
Process(ParamA, ParamD);  
Stop(ParamC);  

It does break encapsulation from a method point of view but not from a class point of view.

Answer 1

In an object-oriented language it is common to pass in dependencies (classes that this class will communicate with) and configuration values in the constructor and only the values to actually be operated on in the function call.

This can actually be more readable. Consider code where you have a service that generates and publishes an invoice. There can be a variety of ways to do the publication – via a web-service that sends it to some sort of centralized server, or via an email sent to someone in the warehouse, or maybe just by sending it to the default printer. However, it is usually simpler for the method calling Publish() to not know the specifics of how the publication is happening – it just needs to know that the publication went off without a hitch. This allows you to think of less things at a time and concentrate on the problem better. Then you are simply making use of an interface to a service (in C#):

// Notice the consuming class needs only know what it does, not how it does it
public interface IInvoicePublisher {
  pubic void Publish(Invoice anInvoice);
}

This could be implemented in a variety of ways, for example:

public class DefaultPrinterInvoicePublisher
  DefaultPrinterInvoicePublisher _printer;
  public DefaultPrinterInvoicePublisher(DefaultPrinterFacade printer) {
    _printer = printer
  }
  public void Publish(Invoice anInvoice) {
    printableObject = //Generate crystal report, or something else that can be printed
    _printer.Print(printableObject);
  }

The code that uses it would then take an IInvoicePublisher as a constructor parameter too so that functionality is available to be used throughout.