Created
February 5, 2024 11:09
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| // See https://aka.ms/new-console-template for more information | |
| using ConsoleApp1; | |
| var nameEntities = new[] { "", null, "Dawid", "Kacper", "Wojciech", "Michał M", "Michał B", "Rafał", "Anna", "Floris" } | |
| .Select(CreateUser).ToList(); | |
| var index = 0; | |
| foreach (var ne in nameEntities) | |
| { | |
| if (ne.TryGetValue(out var u)) Console.WriteLine($"{index++}. User created: {u}"); | |
| if (ne.TryGetError(out var err)) Console.Error.WriteLine($"{index++}. Failed: {err}"); | |
| } | |
| //static Result<MyEnum> Parse(string name) => name switch | |
| //{ | |
| // "A" => MyEnum.A, | |
| // "B" => MyEnum.B, | |
| // "C" => MyEnum.C, | |
| // _ => MyApiExpectedErrors.EnumCannotBeParsed | |
| //}; | |
| static Result<User> CreateUser(string? name) | |
| { | |
| if (string.IsNullOrEmpty(name)) return MyApiExpectedErrors.ValidationFailed; | |
| if (Random.Shared.NextDouble() > 0.8) return MyApiExpectedErrors.DatabaseNotOnline; | |
| try | |
| { | |
| if (Random.Shared.NextDouble() > 0.5) throw new Exception("Something went wrong in upstream"); | |
| return new User(Random.Shared.Next(), name); | |
| } | |
| catch (Exception e) | |
| { | |
| // TODO use logger | |
| var fore = Console.ForegroundColor; | |
| Console.ForegroundColor = ConsoleColor.Red; | |
| Console.Error.WriteLine(e); | |
| Console.ForegroundColor = fore; | |
| return (Error)e.Message; | |
| } | |
| } | |
| enum MyEnum { A, B, C } | |
| public static class MyApiExpectedErrors | |
| { | |
| public static readonly Error DatabaseNotOnline = new("DatabaseNotOnline", "Cannot connect to DB"); | |
| public static readonly Error ValidationFailed = new("ValidationFailed", "Some data is wrong"); | |
| public static readonly Error EnumCannotBeParsed = new("EnumParseFailed", $"Cannot parse enum. Valid labels are: {string.Join(", ", Enum.GetNames<MyEnum>())}"); | |
| } | |
| public record User(int Id, string Name); |
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| #nullable enable | |
| using System.Diagnostics.CodeAnalysis; | |
| namespace ConsoleApp1; | |
| public sealed record Error(string Code, string? Description = null) | |
| { | |
| private const string UNEXPECTED = "UNEXPECTED"; | |
| public static explicit operator Error(string description) => new(UNEXPECTED, description); | |
| } | |
| public class Result<TValue> | |
| { | |
| private readonly TValue? Value; | |
| private readonly Error? Error; | |
| [MemberNotNullWhen(true, nameof(Value))] | |
| [MemberNotNullWhen(false, nameof(Error))] | |
| public bool IsSuccess { get; } | |
| private Result(TValue value) | |
| { | |
| Value = value; | |
| Error = default; | |
| IsSuccess = true; | |
| } | |
| private Result(Error error) | |
| { | |
| Value = default; | |
| Error = error; | |
| IsSuccess = false; | |
| } | |
| public static Result<TValue> Success(TValue value) => new(value); | |
| public static Result<TValue> Failure(Error error) => new(error); | |
| public static implicit operator Result<TValue>(TValue result) => new(result); | |
| public static implicit operator Result<TValue>(Error error) => new(error); | |
| public void Invoke(Action<TValue> success, Action<Error>? failure = null) | |
| { | |
| if (IsSuccess) success(Value); | |
| else failure?.Invoke(Error); | |
| } | |
| public bool TryGetValue([NotNullWhen(true)] out TValue? value) | |
| { | |
| if (IsSuccess) | |
| { | |
| value = Value; | |
| return true; | |
| } | |
| else | |
| { | |
| value = default; | |
| return false; | |
| } | |
| } | |
| public bool TryGetError([NotNullWhen(true)] out Error? error) | |
| { | |
| if (!IsSuccess) | |
| { | |
| error = Error; | |
| return true; | |
| } | |
| else | |
| { | |
| error = default; | |
| return false; | |
| } | |
| } | |
| public override string ToString() | |
| { | |
| if (IsSuccess) return Value.ToString() ?? ""; | |
| else return Error.ToString() ?? ""; | |
| } | |
| } |
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