/*
* Instances allow us to create specific static readonly instances of this type.
*/
internal class InstanceExamples : IScenario
{
public Task Run()
{
VendorInformation vi = new VendorInformation();
Console.WriteLine((bool) (vi.VendorId == VendorId.Unspecified)); // true
Console.WriteLine((bool) (vi.VendorId != VendorId.Invalid)); // true
// from a text file that is screwed, we'll end up with:
var invalidVi = VendorInformation.FromTextFile();
Console.WriteLine((bool) (invalidVi.VendorId == VendorId.Invalid)); // true
return Task.CompletedTask;
}
}
[ValueObject<float>]
[Instance("Freezing", 0.0f)]
[Instance("Boiling", 100.0f)]
[Instance("AbsoluteZero", -273.15f)]
public readonly partial struct Centigrade
{
public static Validation Validate(float value) =>
value >= AbsoluteZero.Value ? Validation.Ok : Validation.Invalid("Cannot be colder than absolute zero");
}
/*
- Instances are the only way to avoid validation, so we can create instances
- that nobody else can. This is useful for creating special instances
- that represent concepts such as 'invalid' and 'unspecified'.
*/
[ValueObject]
[Instance("Unspecified", -1)]
[Instance("Invalid", -2)]
public readonly partial struct Age
{
private static Validation Validate(int value) =>
value > 0 ? Validation.Ok : Validation.Invalid("Must be greater than zero.");
}
[ValueObject]
[Instance("Unspecified", 0)]
[Instance("Invalid", -1)]
public partial class VendorId
{
private static Validation Validate(int value) =>
value > 0 ? Validation.Ok : Validation.Invalid("Must be greater than zero.");
}
[ValueObject<string>]
[Instance("Invalid", "[INVALID]")]
public partial class VendorName
{
}
public class VendorInformation
{
public VendorId VendorId { get; private init; } = VendorId.Unspecified;
public static VendorInformation FromTextFile()
{
// image the text file is screwed...
return new VendorInformation
{
VendorId = VendorId.Invalid
};
}
}
public class VendorRelatedThings
{
public VendorName GetVendorName(VendorId id)
{
if (id == VendorId.Unspecified)
throw new InvalidOperationException("The vendor ID was unspecified");
// throw if invalid
if (id == VendorId.Invalid)
throw new InvalidOperationException("The vendor ID was invalid");
// or record it as invalid
if (id == VendorId.Invalid) return VendorName.Invalid;
