Referer

IRefererBase is the root interface for consumers that get a reference to inner parts of objects.

/// <summary>Accessor referer that can return a reference to a value.</summary>
public interface IRefererBase : IWriterBase { }

IRefererBase<From, To> describes writers that get a 'ref' to specific object and value type.

/// <summary>Accessor referer that can return a reference to a value.</summary>
public interface IRefererBase<From, To> : IRefererBase, IRefererFrom<From>, IRefererTo<To>, IWriterTypes { }

/// <summary>Accessor referer that can return a reference to a value.</summary>
public interface IReferer<From, To> : IRefererBase<From, To> where From : notnull
{
    /// <summary>Can get accessor reference</summary>
    bool CanRefer { get; }

    /// <summary>Get reference to accessor.</summary>
    /// <param name="from"></param>
    /// <returns>False if write is not supported with given arguments.</returns>
    /// <exception cref="Exception">Unexpected error.</exception>
    ref To GetReference(From from, IServiceProvider? context = null);
}

/// <summary>Accessor referer that can return a reference to a accessor by record reference.</summary>
public interface IRefererFromRef<From, To> : IRefererBase<From, To> where From : notnull
{
    /// <summary>Can get accessor reference</summary>
    bool CanRefer { get; }

    /// <summary>Get reference to accessor.</summary>
    /// <param name="from"></param>
    /// <returns>False if write is not supported with given arguments.</returns>
    /// <exception cref="Exception">Unexpected error.</exception>
    ref To GetReference(ref From from, IServiceProvider? context = null);
}

IRefererBase is specialization of IWriterBase.

IWriterBase
└── IRefererBase
    └── IRefererBase<From, To>
        ├── IReferer<From, To>
        └── IRefererFromRef<From, To>

IReferer<From, To> gets reference to inner content of class.

// Create label referer
IReferer<MyClass, string> referer =
    DelegateWriter.Refer((MyClass myClass) => ref myClass.label);
// Create class
MyClass myClass = new MyClass("A", 1);
// Get reference to 'label'
ref string label = ref referer.GetReference(myClass);

IRefererFromRef<From, To> gets reference to inner content of struct.

// Create label referer
IRefererFromRef<MyStruct, string> referer =
    DelegateWriter.Refer((ref MyStruct myStruct) => ref myStruct.label);
// Create struct
MyStruct myStruct = new MyStruct("A", 1);
// Get reference to 'label'
ref string label = ref referer.GetReference(ref myStruct);

.TypeCastFromObject() casts 'From' type to object. For structs takes reference into box.

// Create 'MyClass' label referer
IReferer<object, string> classReferer =
    DelegateWriter.Refer((MyClass myClass) => ref myClass.label)
    .TypeCastFromObject();
// Create 'MyStruct' label referer
IReferer<object, string> structReferer =
    DelegateWriter.Refer((ref MyStruct myStruct) => ref myStruct.label)
    .TypeCastFromObject();

// Create instances
object myClass = new MyClass("A", 1);
object myStruct = new MyStruct("A", 1);

// Get reference to 'label'
ref string classLabel = ref classReferer.GetReference(myClass);
ref string structLabel = ref structReferer.GetReference(myStruct);

Visitor

IRefererVisitor is the visitor interface for refer visitor implementations. Invoked from IWriterBase.Accept(IWriterVisitorBase).

/// <summary>Referer visitor</summary>
public interface IRefererVisitor : IWriterBaseVisitor
{
    /// <summary>Try visit <paramref name="refererT"/>.</summary>
    /// <returns>true to continue visitation</returns>
    bool Visit<From, To>(IReferer<From, To> refererT) where From : notnull;
    /// <summary>Try visit <paramref name="refererTFR"/>.</summary>
    /// <returns>true to continue visitation</returns>
    bool Visit<From, To>(IRefererFromRef<From, To> refererTFR) where From : notnull;
    /// <summary>Try visit <paramref name="referer"/>.</summary>
    /// <returns>true to continue visitation</returns>
    bool Visit(IReferer referer);
    /// <summary>Try visit <paramref name="refererFR"/>.</summary>
    /// <returns>true to continue visitation</returns>
    bool Visit(IRefererFromRef refererFR);
}

Full Example

Full example

using Avalanche.Writer;

class referer
{
    public static void Run()
    {
        {
            // <01>
            // Create label referer
            IReferer<MyClass, string> referer =
                DelegateWriter.Refer((MyClass myClass) => ref myClass.label);
            // Create class
            MyClass myClass = new MyClass("A", 1);
            // Get reference to 'label'
            ref string label = ref referer.GetReference(myClass);
            // </01>

            object box = myClass;
            IReferer<object, string> refererFromObject = (IReferer<object, string>)referer;
            ref string label2 = ref refererFromObject.GetReference(box);
        }
        {
            // <02>
            // Create label referer
            IRefererFromRef<MyStruct, string> referer =
                DelegateWriter.Refer((ref MyStruct myStruct) => ref myStruct.label);
            // Create struct
            MyStruct myStruct = new MyStruct("A", 1);
            // Get reference to 'label'
            ref string label = ref referer.GetReference(ref myStruct);
            // </02>

            object box = myStruct;
            IReferer<object, string> refererFromObject = (IReferer<object, string>)referer;
            ref string label2 = ref refererFromObject.GetReference(box);
        }
        {
            // <03>
            // Create 'MyClass' label referer
            IReferer<object, string> classReferer =
                DelegateWriter.Refer((MyClass myClass) => ref myClass.label)
                .TypeCastFromObject();
            // Create 'MyStruct' label referer
            IReferer<object, string> structReferer =
                DelegateWriter.Refer((ref MyStruct myStruct) => ref myStruct.label)
                .TypeCastFromObject();

            // Create instances
            object myClass = new MyClass("A", 1);
            object myStruct = new MyStruct("A", 1);

            // Get reference to 'label'
            ref string classLabel = ref classReferer.GetReference(myClass);
            ref string structLabel = ref structReferer.GetReference(myStruct);
            // </03>
        }
    }

    public record MyClass
    {
        public string label;
        public int id;

        public MyClass(string label, int id) { this.label = label; this.id = id; }

        public void Print(string value) { }
    }

    public record struct MyStruct
    {
        public string label;
        public int id;

        public MyStruct(string label, int id) { this.label = label; this.id = id; }

        public void Print(string value) { }
    }

}