C#•12mo ago

❔ How to fix "Target runtime doesn't support covariant types in overrides?

I have Builder, let's see code:

public abstract class UISchemaBuilderBase
{
   protected readonly UISchemaSpecification UiSchemaSpecification;

   public UISchemaSpecification Builder() =>
      UiSchemaSpecification;

   public virtual UISchemaBuilderBase AddBoolean(
       string fieldName,
       string groupName = null)

   {
       .. some logic
    
       UiSchemaSpecification.Properties[ fieldName ] = schema;
       return this;
   }
}

public class UISchemaBuilder : UISchemaBuilderBase
{
    public UISchemaBuilder() : base(new UISchemaSpecification()) { }

    public UISchemaGroupBuilder StartGroup(string name)
    {
        UiSchemaSpecification.ParsecMetadata ??= new();
        UiSchemaSpecification.ParsecMetadata.Groups ??= new();
        UiSchemaSpecification.ParsecMetadata.Groups.Add( new(name) );

        return new UISchemaGroupBuilder(name, this, UiSchemaSpecification);
    }
}

public class UISchemaGroupBuilder : UISchemaBuilderBase
{
    private readonly string _name;
    private readonly UISchemaBuilder _schemaBuilder;

    public UISchemaGroupBuilder(
       string name,
       UISchemaBuilder schemaBuilder,
       UISchemaSpecification specification)
       : base(specification)
    {
        _name = name;
        _schemaBuilder = schemaBuilder;
    }

   public override UISchemaGroupBuilder AddBoolean(
       string fieldName,
       string fieldTitle,
       string groupName = null)
    {
        base.AddBoolean(fieldName, fieldTitle, _name);
        return this;
    }
}

public abstract class UISchemaBuilderBase
{
   protected readonly UISchemaSpecification UiSchemaSpecification;

   public UISchemaSpecification Builder() =>
      UiSchemaSpecification;

   public virtual UISchemaBuilderBase AddBoolean(
       string fieldName,
       string groupName = null)

   {
       .. some logic
    
       UiSchemaSpecification.Properties[ fieldName ] = schema;
       return this;
   }
}

public class UISchemaBuilder : UISchemaBuilderBase
{
    public UISchemaBuilder() : base(new UISchemaSpecification()) { }

    public UISchemaGroupBuilder StartGroup(string name)
    {
        UiSchemaSpecification.ParsecMetadata ??= new();
        UiSchemaSpecification.ParsecMetadata.Groups ??= new();
        UiSchemaSpecification.ParsecMetadata.Groups.Add( new(name) );

        return new UISchemaGroupBuilder(name, this, UiSchemaSpecification);
    }
}

public class UISchemaGroupBuilder : UISchemaBuilderBase
{
    private readonly string _name;
    private readonly UISchemaBuilder _schemaBuilder;

    public UISchemaGroupBuilder(
       string name,
       UISchemaBuilder schemaBuilder,
       UISchemaSpecification specification)
       : base(specification)
    {
        _name = name;
        _schemaBuilder = schemaBuilder;
    }

   public override UISchemaGroupBuilder AddBoolean(
       string fieldName,
       string fieldTitle,
       string groupName = null)
    {
        base.AddBoolean(fieldName, fieldTitle, _name);
        return this;
    }
}

So implemented code allows use to do this:

var builder = new UISchemaBuilder()
  .StartGroup("groupName")
    .AddBoolean()
  .EndGroup()
  .StartGroup("anotherGroupName")
    .AddBoolean()
  .EndGroup()
  .Build();

var builder = new UISchemaBuilder()
  .StartGroup("groupName")
    .AddBoolean()
  .EndGroup()
  .StartGroup("anotherGroupName")
    .AddBoolean()
  .EndGroup()
  .Build();

22 Replies

SWEETPONY•12mo ago

The problem is: I can't do the same in netstandard and I don't understand how to fix this.. I should change return type of methods in UISchemaGroupBuilder. For example AddText should return UISchemaBuilderBase, not UISchemaGroupBuilder. But if I follow by these advices, my builder wouldn't work. I can't use EndGroup after AddBoolean for example. Can someone help me, please?

ero•12mo ago

why do you need to change the type exactly?

SWEETPONY•12mo ago

I can make some changes for netstandard:

+ public override UISchemaBuilderBase AddBoolean
- public override UISchemaGroupBuilder AddBoolean

+ public override UISchemaBuilderBase AddBoolean
- public override UISchemaGroupBuilder AddBoolean

but my builder will not work I can't use EndGroup after AddBoolean

public UISchemaBuilder EndGroup() =>
   _schemaBuilder;

public UISchemaBuilder EndGroup() =>
   _schemaBuilder;

ero•12mo ago

so, okay, explain this to me, how can you even override AddBoolean like that you're adding a parameter how is that possible?

MODiX•12mo ago

ero

REPL Result: Failure

class C
{
  public virtual void M(string s1, string s2 = "") { }
}

class D : C
{
  public override void M(string s1, string s2, string s3) => base.M(s1, s2, s3);
}

class C
{
  public virtual void M(string s1, string s2 = "") { }
}

class D : C
{
  public override void M(string s1, string s2, string s3) => base.M(s1, s2, s3);
}

Exception: CompilationErrorException

- 'D.M(string, string, string)': no suitable method found to override
- No overload for method 'M' takes 3 arguments

- 'D.M(string, string, string)': no suitable method found to override
- No overload for method 'M' takes 3 arguments

Compile: 473.613ms | Execution: 0.000ms | React with ❌ to remove this embed.

ero•12mo ago

SWEETPONY•12mo ago

one moment

SWEETPONY•12mo ago

https://github.com/INTERNALINTERFERENCE/CovariantTest

GitHub

GitHub - INTERNALINTERFERENCE/CovariantTest

Contribute to INTERNALINTERFERENCE/CovariantTest development by creating an account on GitHub.

SWEETPONY•12mo ago

simple repo

ero•12mo ago

it just seems like you're approaching this kinda incorrectly

SWEETPONY•12mo ago

idk it works on net6 ahh I found how to fix this public new UISchemaGroupBuilder AddBoolean()

ero•12mo ago

an interface with TSelf might be better your abstract class doesn't even have any abstract members

SWEETPONY•12mo ago

can you show an example?

ero•12mo ago

on it

SWEETPONY•12mo ago

public abstract class UISchemaBuilderBase<TSchemaBuilder>
    where TSchemaBuilder : UISchemaBuilderBase<TSchemaBuilder>
{
    public virtual TSchemaBuilder AddBoolean() =>
       throw new NotImplementedException();
}

public class UISchemaBuilder : UISchemaBuilderBase<UISchemaBuilder>
{
    public override UISchemaBuilder AddBoolean() => 
        throw new NotImplementedException();
}

public abstract class UISchemaBuilderBase<TSchemaBuilder>
    where TSchemaBuilder : UISchemaBuilderBase<TSchemaBuilder>
{
    public virtual TSchemaBuilder AddBoolean() =>
       throw new NotImplementedException();
}

public class UISchemaBuilder : UISchemaBuilderBase<UISchemaBuilder>
{
    public override UISchemaBuilder AddBoolean() => 
        throw new NotImplementedException();
}

such that?

MODiX•12mo ago

ero

REPL Result: Success

Builder builder = new Builder()
  .AddBoolean("", "")
  .StartGroup()
    .AddBoolean("", "")
    .EndGroup();

interface IBuilder<out TSelf>
  where TSelf : IBuilder<TSelf>
{
  TSelf AddBoolean(string fieldName, string fieldTitle, string groupName = null);
}

class Builder : IBuilder<Builder>
{
  public Builder AddBoolean(string fieldName, string fieldTitle, string groupName = null)
  {
    return this;
  }

  public GroupBuilder StartGroup()
  {
    return new(this);
  }
}

class GroupBuilder : IBuilder<GroupBuilder>
{
  private readonly Builder _parent;

  public GroupBuilder(Builder parent)
  {
    _parent = parent;
  }

  public GroupBuilder AddBoolean(string fieldName, string fieldTitle, string groupName = null)
  {
    return this;
  }

  public Builder EndGroup()
  {
    return _parent;
  }
}

Builder builder = new Builder()
  .AddBoolean("", "")
  .StartGroup()
    .AddBoolean("", "")
    .EndGroup();

interface IBuilder<out TSelf>
  where TSelf : IBuilder<TSelf>
{
  TSelf AddBoolean(string fieldName, string fieldTitle, string groupName = null);
}

class Builder : IBuilder<Builder>
{
  public Builder AddBoolean(string fieldName, string fieldTitle, string groupName = null)
  {
    return this;
  }

  public GroupBuilder StartGroup()
  {
    return new(this);
  }
}

class GroupBuilder : IBuilder<GroupBuilder>
{
  private readonly Builder _parent;

  public GroupBuilder(Builder parent)
  {
    _parent = parent;
  }

  public GroupBuilder AddBoolean(string fieldName, string fieldTitle, string groupName = null)
  {
    return this;
  }

  public Builder EndGroup()
  {
    return _parent;
  }
}

Compile: 660.359ms | Execution: 45.369ms | React with ❌ to remove this embed.

SWEETPONY•12mo ago

hm interesting! I like the interface usage @just_ero May I ask an immodest question? how long have you been programming in C#?

ero•12mo ago

i don't think i can answer that very clearly cause i don't do it professionally and i have never really completed a project

Vi Ness•12mo ago

That's a mood

ero•12mo ago

so i mean, i guess the first time i coded in c# was like 6 years ago or something (maybe more?) but it's not like i've just been grinding away at my programming skills every day i've never even read any books or watched tutorials

SWEETPONY•12mo ago

incredible

Accord•12mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ How to fix "Target runtime doesn't support covariant types in overrides?