Interface IIterator<T>

An alternative interface to IEnumerator<T> that provides access to a sequence of elements.

Namespace: Recore.Collections.Generic
Assembly: Recore.dll
Syntax
public interface IIterator<out T>
Type Parameters
Name Description
T
Remarks

This interface is meant to resemble Java's concept of an iterator. While using IEnumerator<T> usually provides safer access to a collection than, say, manipulating indices directly in a list, there are times where it is clumsy to use.

Examples

A common case is calling an API that needs to tell its caller whether it should be called again. In order to do this with IEnumerator<T>, the API must look ahead to the next element with MoveNext() before returning and then maintain this state between calls.

For example, consider this type that gets status information on a customer's order from some external source:

using System.Collections.Generic;

class OrderStatusUpdater
{
    private readonly IEnumerator<string> statusEnumerator;

    private string currentStatus = null;

    // We need to look ahead so we know when we've returned the last element
    private string nextStatus = null;
    private bool isFinished = false;

    public OrderStatusUpdater(IEnumerable<string> statuses)
    {
        statusEnumerator = statuses.GetEnumerator();
        UpdateStatus();
    }

    private void UpdateStatus()
    {
        currentStatus = nextStatus;

        if (statusEnumerator.MoveNext())
        {
            nextStatus = statusEnumerator.Current;
        }
        else
        {
            isFinished = true;
        }
    }

    public OrderStatus GetStatusUpdate()
    {
        UpdateStatus();

        return new OrderStatus
        {
            Status = currentStatus,
            IsFinished = isFinished
        };
    }
}

Now consider the code with IIterator<T>:

using System.Collections.Generic;
using Recore.Collections.Generic;

class OrderStatusUpdater
{
    private readonly IIterator<string> statusIterator;

    private string currentStatus = null;

    public OrderStatusUpdater(IEnumerable<string> statuses)
    {
        statusIterator = Iterator.FromEnumerable(statuses);
    }

    public OrderStatus GetStatusUpdate()
    {
        if (statusIterator.HasNext)
        {
            currentStatus = statusIterator.Next();
        }

        return new OrderStatus
        {
            Status = currentStatus,
            IsFinished = !statusIterator.HasNext
        };
    }
}

Properties

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HasNext

Whether the sequence has more elements.

Declaration
bool HasNext { get; }
Property Value
Type Description
Boolean

Methods

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Next()

Advances the iterator to the next element and returns it.

Declaration
T Next()
Returns
Type Description
T

Extension Methods