Should business objects be able to create their own DTOs?
- by Sam
Suppose I have the following class:
class Camera
{
public Camera(
double exposure,
double brightness,
double contrast,
RegionOfInterest regionOfInterest)
{
this.exposure = exposure;
this.brightness = brightness;
this.contrast = contrast;
this.regionOfInterest = regionOfInterest;
}
public void ConfigureAcquisitionFifo(IAcquisitionFifo acquisitionFifo)
{
// do stuff to the acquisition FIFO
}
readonly double exposure;
readonly double brightness;
readonly double contrast;
readonly RegionOfInterest regionOfInterest;
}
... and a DTO to transport the camera info across a service boundary (WCF), say, for viewing in a WinForms/WPF/Web app:
using System.Runtime.Serialization;
[DataContract]
public class CameraData
{
[DataMember]
public double Exposure { get; set; }
[DataMember]
public double Brightness { get; set; }
[DataMember]
public double Contrast { get; set; }
[DataMember]
public RegionOfInterestData RegionOfInterest { get; set; }
}
Now I can add a method to Camera to expose its data:
class Camera
{
// blah blah
public CameraData ToData()
{
var regionOfInterestData = regionOfInterest.ToData();
return new CameraData()
{
Exposure = exposure,
Brightness = brightness,
Contrast = contrast,
RegionOfInterestData = regionOfInterestData
};
}
}
or, I can create a method that requires a special IReporter to be passed in for the Camera to expose its data to. This removes the dependency on the Contracts layer (Camera no longer has to know about CameraData):
class Camera
{
// beep beep I'm a jeep
public void ExposeToReporter(IReporter reporter)
{
reporter.GetCameraInfo(exposure, brightness, contrast, regionOfInterest);
}
}
So which should I do? I prefer the second, but it requires the IReporter to have a CameraData field (which gets changed by GetCameraInfo()), which feels weird. Also, if there is any even better solution, please share with me! I'm still an object-oriented newb.
