Best practices for working with dynamic units?

[Mobz87]

I'm working on a program where the customer wants to be able to change the 'default units'.

ex
In a Settings-tab:
Pressure (choose) Bar or Pascal.
If you select 'Bar' then all input and output are displayed in Bar.

Right now I have hard coded it like:

Pressure = Pressure.FromBars(Control.Value);

OutputBox = Pressure.ToUnit(PressureUnit.Bar).ToString();

What is Best practices for making dynamic units?

[tmilnthorp]

I would generally populate a combo box with the pressure units. I use a wrapper like so to store a string/value:

internal class ComboBoxItemWrapper<T>
{
	private T item;
	private readonly Func<ComboBoxItemWrapper<T>, string> toStringMethod;

	public ComboBoxItemWrapper( T item, string text )
	{
		this.item = item;
		this.toStringMethod = cbiw => text;
	}

	public ComboBoxItemWrapper( T item, Func<ComboBoxItemWrapper<T>, string> toStringMethod )
	{
		this.item = item;
		this.toStringMethod = toStringMethod;
	}

	public override bool Equals( object obj )
	{
		if( obj is T )
			return Item.Equals( obj );
		else
			return base.Equals( obj );
	}

	public T Item
	{
		get { return item; }
	}

	public override string ToString()
	{
		return toStringMethod( this );
	}
}

And populate a combo box like so:

foreach( PressureUnit unit in Enum.GetValues( typeof( PressureUnit ) ) )
{
	if( unit == PressureUnit.Undefined )
		continue;

	var comboBoxItem = new ComboBoxItemWrapper<PressureUnit>( unit, UnitAbbreviationsCache.Default.GetDefaultAbbreviation( unit ) );
	pressureChoiceComboBox.Items.Add( comboBoxItem );
}

Then you can switch like so:

var selectedPressureUnit = ( (ComboBoxItemWrapper<PressureUnit>)pressureChoiceComboBox.SelectedValue ).Item;
var pressure = Pressure.From( Control.Value, selectedPressureUnit );

[angularsen]

I think you should get far by using this:

• Pressure.From(value, selectedUnit) for reading input values in the configured default unit
• myPressure.ToUnit(selectedUnit).ToString() for showing the value and unit as a string
• myPressure.As(selectedUnit) for showing the value in the default unit

[Mobz87]

Thanks you two for your feedback!

If I make a new pressure unit:
Pressure _pressure = new Pressure((double)Control.Value, DefaultUnit);

And then change its unit:
_pressure.As(NewUnit);

Displaying it value:
Debug.Print(_pressure.Value);

The output is displayed as the DefaultUnit and not the NewUnit.
It is a mistake or have I misunderstod its functionality?

Also if I do:
Debug.Print(_pressure.Unit.ToString());

It prints it name: poundspersquareinch
And not its unit: Psi

Is there another way to display its units rather then its name?

[tmilnthorp]

_pressure.As(NewUnit); does not change the value of _pressure, it returns the converted pressure.

var converted = _pressure.As(NewUnit);
Debug.Print(converted.Value);

As for the unit, it's just an enum. In that case you're doing a .ToString on an enum.

To get the abbreviation, do the following:

UnitAbbreviationsCache.Default.GetDefaultAbbreviation(NewUnit)

[angularsen]

To be clear, converted here is double not Pressure.

double converted = _pressure.As(NewUnit);

To change the unit, use ToUnit().

Is it possible you simply want to do this?

string psiText = _pressure.ToUnit(PressureUnit.PoundForcePerSquareInch).ToString(); // "20 psi"

[angularsen]

@Mobz87 There is a pretty big PR #576 on the way to greatly improve working dynamically with units.

Please see the PR's updated README.

[MrFoged]

To be clear, converted here is double not Pressure.

double converted = _pressure.As(NewUnit);

To change the unit, use ToUnit().

Is it possible you simply want to do this?

string psiText = _pressure.ToUnit(PressureUnit.PoundForcePerSquareInch).ToString(); // "20 psi"

I just want it without the 20 - so just the psi

Right now I can get the value + unit:
Ex 20 psi

Or I can get the value:
Ex 20

Or I can get the name:
PoundForcePerSquareInch (Name of enum)

Im just missing the unit in a string:
psi

@angularsen Looks great that you're already looking into improve working dynamically with units!

[angularsen]

Ah, then what Tristan proposed should work for you.

To get the abbreviation, do the following:

UnitAbbreviationsCache.Default.GetDefaultAbbreviation(PressureUnit.PoundForcePerSquareInch) // "psi"

[MrFoged]

I posted from the the wrong account :-)
Thanks I just do that!

[angularsen]

Ok, I'm closing this issue. Just reopen if there is anything else.