Iterating over C # Iterator (IEnumerable) in Matlab

Question

I have a C # method that returns a very large number of objects. This should be consumed in Matlab.

namespace MyNameSpace{
    public static class MyClass{
        public static IEnumerable<MyDataObject> GetVeryLargeResponse(){
            while(CheckForSomeFunkyConditionThatsRarelyTrue()){
               yield return GetMyNextDataObject();
            }
            yield break;
        }
    }
}

In matlab when i call

result = MyClass.GetVeryLargeResponse();

I expect the result to be of type IEnumerable<MyDataObject>to be able to get Enumerator<MyDataObject>by invoking result.GetEnumerator().

Where do I get resultthat is of type MyNameSpace.<GetVeryLargeResponse>d_3without method GetEnumerator(). I see one of the resultSuper class has System.Collections.Generic.IEnumerable<MyClass>.

Is there a way that I can iterate over this in Matlab or even "cast" resultto IEnumerable<MyClass>in Matlab.

ps

• Convert to Array/ IListetc impossible due to data volume
• # IEnumerable Matlab?, IQueryable .
• Matlab 2010b

Answer 1

GetEnumerator() - .

Matlab , , :

public static class Extensions
{
    public static EnumerableWrapper<T> Wrap<T>(this IEnumerable<T> source)
    {
        return new EnumerableWrapper<T>(source);
    }
}

public class EnumerableWrapper<T> : IEnumerable<T>
{
    private readonly IEnumerable<T> source;

    public EnumerableWrapper(IEnumerable<T> source)
    {
        this.source = source;
    }

    public IEnumerator<T> GetEnumerator()
    {
        return new EnumeratorWrapper<T>(source.GetEnumerator());
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}

public class EnumeratorWrapper<T> : IEnumerator<T>
{
    private readonly IEnumerator<T> source;

    public EnumeratorWrapper(IEnumerator<T> source)
    {
        this.source = source;
    }

    public T Current { get { return source.Current; } }

    object IEnumerator.Current { get { return Current; } }

    public bool MoveNext()
    {
        return source.MoveNext();
    }

    public void Reset()
    {
        source.Reset();
    }

    public void Dispose()
    {
        source.Dispose();
    }

}

:

result = MyClass.GetVeryLargeResponse().Wrap();

, Matlab , ...

Answer 2

:

MyClass.cs

namespace MyNameSpace {
    public class Person {
        public string name { get; set; }
        public int age { get; set; }
    }

    public class MyClass {
        private static List<Person> people = new List<Person> {
            new Person {name = "name1", age=10},
            new Person {name = "name2", age=20},
            new Person {name = "name3", age=30},
            new Person {name = "name4", age=40},
            new Person {name = "name5", age=50}
        };

        public static IEnumerable<Person> GetPeople() {
            foreach (var p in people) {
                yield return p;
            }
        }
    }
}

code.m

%# load my assembly
str = 'C:\path\to\MyNameSpace.dll';
NET.addAssembly(str);

obj = MyNameSpace.MyClass.GetPeople();   %# IEnumerable<Person>

%# call ToArray() extension method: this forces immediate query evaluation
NET.addAssembly('System.Core');          %# contains 'System.Linq' namespace
arr = NET.invokeGenericMethod('System.Linq.Enumerable', 'ToArray', ...
    {'MyNameSpace.Person'}, obj);

%# loop through results
for i=1:arr.Length
    fprintf('name=%s, age=%d\n', char(arr(i).name), int32(arr(i).age));
end

:

name=name1, age=10
name=name2, age=20
name=name3, age=30
name=name4, age=40
name=name5, age=50

, Person[] (, , ). , :

>> superclasses(obj)
Superclasses for class MyNameSpace.<GetPeople>d__0:
    System.Object
    System.Collections.Generic.IEnumerable<MyNameSpace*Person>
    System.Collections.IEnumerable
    System.Collections.Generic.IEnumerator<MyNameSpace*Person>
    System.IDisposable
    System.Collections.IEnumerator
    handle

System.Collections.Generic.IEnumerator<Person>, - , , GetEnumerator:

>> methods(obj,'-full')

Methods for class MyNameSpace.<GetPeople>d__0:

MyNameSpace.<GetPeople>d__0 obj <GetPeople>d__0(int32 scalar <>1__state)
logical scalar RetVal Equals(MyNameSpace.<GetPeople>d__0 this, System.Object obj)
int32 scalar RetVal GetHashCode(MyNameSpace.<GetPeople>d__0 this)
System.Type RetVal GetType(MyNameSpace.<GetPeople>d__0 this)
System.String RetVal ToString(MyNameSpace.<GetPeople>d__0 this)
event.listener L addlistener(handle sources, char vector eventname, function_handle scalar callback)  % Inherited from handle
event.proplistener L addlistener(handle sources, meta.property properties, char vector eventname, function_handle scalar callback)  % Inherited from handle
event.proplistener L addlistener(handle sources, string propertyname, char vector eventname, function_handle scalar callback)  % Inherited from handle
event.proplistener L addlistener(handle sources, cell propertynames, char vector eventname, function_handle scalar callback)  % Inherited from handle
delete(handle obj)  % Inherited from handle
logical TF eq(A, B)  % Inherited from handle
handle HM findobj(handle H, varargin)  % Inherited from handle
meta.property prop findprop(handle scalar object, string propname)  % Inherited from handle
logical TF ge(A, B)  % Inherited from handle
logical TF gt(A, B)  % Inherited from handle
logical validity isvalid(handle obj)  % Inherited from handle
logical TF le(A, B)  % Inherited from handle
logical TF lt(A, B)  % Inherited from handle
logical TF ne(A, B)  % Inherited from handle
notify(handle sources, string eventname)  % Inherited from handle
notify(handle sources, string eventname, event.EventData scalar eventdata)  % Inherited from handle

Answer 3

You need to use explicit casts. First, I explicitly pass the IEnumerable instance:

result = MyClass.GetVeryLargeResponse();
resultEnumerable = NET.explicitCast(result,'System.Collections.IEnumerable');

Then enter the enumerator:

resultEnumerator = resultEnumerable.GetEnumerator();

Then, we explicitly list the enumeration:

resultEnumerator = NET.explicitCast(resultEnumerator, 'System.Collections.IEnumerator');

Then you can iterate over the collection as desired:

while (resultEnumerator.MoveNext)
    resultEnumerator.Current
end