Assumptions when using interfaces

From: Mike (michaelloll_at_hotmail.com)
Date: 02/16/05

  • Next message: Dmitry A. Kazakov: "Re: Disadvantages of Inheritance, Polymorphism and Encapsulation" 
    Date: 15 Feb 2005 19:31:00 -0800

    Hello all:

    I had a question about interfaces. I am writing a piece of software
    that in theory will allow programmers to submit jobs to be run on a
    network. Like a grid, but not that advanced. All jobs must follow a
    set of interfaces - originally I had used abstract classes in a
    hierarchy, but I wanted to use interfaces to not force my users to
    inherit from base classes.

    Anyhow, basically my question revolves around one to many
    relationships. I have an interface IJob which has various properties,
    one of which is a collection of ITask, another interface. An IJob
    contains a collection of ITask via its getTasks method (there is no
    setter needed, I beleive, since my execution engine only ever reads the
    tasks, it never sets them; so the developer using my interfaces would
    load his tasks however he saw fit).

    Throughout the life of an object implementing ITask, the status of an
    ITask will be udpated via its UpdateStatus method. So far, I have
    something like (pseudo-language):

    Interface IJob
      collection GetTasks()

    Interface ITask
      void SetStatus(string)
      string GetStatus()

    Now, I beleive I can't make assumptions about how consumers of my
    framework will stores there ITasks ... what I mean is, if I modify an
    ITask obtained from a call to IJob::GetTasks, I can't assume that the
    modification will be persisted between calls to GetTasks, right?

    So if I did this:

    job.GetTasks()[0].SetStatus("Processing")

    I can't guarantee that this is true in a subsequent call:

    job.GetTasks()[0].GetStatus() == "Processing"

    Right?

    I should store the tasks myself in an array or something while I am
    using them.

    Any help is appreciated. What can I assume? Any guidance is
    appreciated. Are there any good texts on using interfaces like this.

    Thanks. 

    -- 
Mike
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