RSCG – OneOf

RSCG – OneOf
 
 

Functional discriminated unions

This is how you can use OneOf .

The code that you start with is

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="OneOf" Version="3.0.255" />
    <PackageReference Include="OneOf.SourceGenerator" Version="3.0.255" />
  </ItemGroup>
 <PropertyGroup>
        <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
        <CompilerGeneratedFilesOutputPath>$(BaseIntermediateOutputPath)\GX</CompilerGeneratedFilesOutputPath>
    </PropertyGroup>
</Project>

The code that you will use is

using OneOfDemo;

Console.WriteLine("Please enter data - string or number");

var data= Console.ReadLine();
//you can experiment with
StringOrNumber nr1 = 5;
var nr = new StringOrNumber(data);
var dataNumber = nr.TryGetNumber();
Console.WriteLine($"{dataNumber.isNumber} {dataNumber.number}");

using OneOf;
namespace OneOfDemo;

[GenerateOneOf]
public partial class StringOrNumber : OneOfBase<string,int> {
    public (bool isNumber,int number) TryGetNumber() =>
           Match( //this match function is auto generated
               s => (int.TryParse(s,out var n),n),
               i => (true,i)
           );
}

The code that is generated is

// <auto-generated />
using System;

#pragma warning disable 1591

namespace OneOf
{
    [AttributeUsage(AttributeTargets.Class,Inherited = false,AllowMultiple = false)]
    internal sealed class GenerateOneOfAttribute : Attribute
    {
    }
}

// <auto-generated />
#pragma warning disable 1591

namespace OneOfDemo
{
    partial class StringOrNumber
    {
        public StringOrNumber(OneOf.OneOf<string,int> _) : base(_) { }

        public static implicit operator StringOrNumber(string _) => new StringOrNumber(_);
        public static explicit operator string(StringOrNumber _) => _.AsT0;

        public static implicit operator StringOrNumber(int _) => new StringOrNumber(_);
        public static explicit operator int(StringOrNumber _) => _.AsT1;
    }
}

Code and pdf at

https://ignatandrei.github.io/RSCG_Examples/v2/docs/OneOf