Custom UI Binding objects to controls

Question

I am creating my own UI Binding system, which ties controls to their associated objects. What would be better than using a series of if-statements? If I add new controls to serve new track items, I would not want to update this series of if statements every time.

TimelineTrackControl control;
Type objectType = track.GetType();

if (objectType == typeof(ShotTrack))
{
    control = new ShotTrackControl();
}
else if (objectType == typeof(AudioTrack))
{
    control = new AudioTrackControl();
}
else if (objectType == typeof(GlobalItemTrack))
{
    control = new GlobalItemTrackControl();
}
else
{
    control = new TimelineTrackControl();
}

control.TargetTrack = track;
timelineTrackMap.Add(track, control);

Dmitry · Accepted Answer · 2014-04-14 17:39:44Z

1

You could:

Create a Dictionary<Type, Type> that contains the track types and the corresponding control types:

private static readonly Dictionary<Type, Type> ControlTypes = new Dictionary<Type, Type>
{
    { typeof(ShotTrack), typeof(ShotTrackControl) },
    ...
};

To get a corresponding control:

control = Activator.CreateInstance(ControlTypes[track.GetType()]);

Create a Dictionary<Type, Func<Control>> that contains the track types and the corresponding control creators:

private static readonly Dictionary<Type, Func<Control>> ControlTypes = new Dictionary<Type, Func<Control>>
{
    { typeof(ShotTrack), () => new ShotTrackControl() },
    ...
};

To create a new corresponding control:

control = ControlTypes[track.GetType()]();

Define a custom attribute that stores the corresponding control type:

[AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
public class TrackControlAttribute : Attribute
{
    public readonly Type ControlType;

    public TrackControlAttribute(Type controlType)
    {
        ControlType = controlType;
    }
}

[TrackControl(typeof(ShotTrackControl))]
public class ShotTrack
{
    ...
}

To create a new corresponding control:

object[] attrs = track.GetType().GetCustomAttributes(typeof(TrackControlAttribute), true);
if (attrs.Length != 0);
    control = Activator.CreateInstance(((TrackControlAttribute)attrs[0]).ControlType);

EDIT
Bug fixed in the 3rd option.

edited Apr 14, 2014 at 17:39

answered Apr 14, 2014 at 16:15

Dmitry

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2 Comments

Adrian Over a year ago

I really like option #3. Though I think I will make the Attribute for the control and point to it's track. That way the tracks have no knowledge of the controls.

Dmitry Over a year ago

Oops. I made a mistake in the getting of the attribute. I updated the sample.

kat0r · Accepted Answer · 2014-04-14 15:51:16Z

1

You could use reflection, in this case http://msdn.microsoft.com/en-us/library/vstudio/d133hta4 like this:

Activator.CreateInstance(null, track.GetType().toString() + "Control");

answered Apr 14, 2014 at 15:51

kat0r

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1 Comment

Adrian Over a year ago

This is a nice answer, but will only really work if you keep your class names consistent.

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