SITUATION:
I have a class "MainClass" that has an indexer "SubClass1Index er".
This indexer returns an instance that implements a particular
interface "ISubClass1 ". This interface defines another indexer
"SubClass2Index er". Bellow is some code with comments. It should
compile.
PROBLEM:
I would like to write something like this:
MainClass cm = new MainClass();
cm.SubClass1Val ues[0].SubClass2Value s[0].ToString();
Note that "SubClass2Index er" needs access to an internal field of
"SubClass1" . This only seems to be possible if a field is allowed in
an interface, i.e. ISubClass1. That is not the case, though.
NONE IDEAL SOLUTIONS:
1) Make "this[]" in SubClass2Indexe r aware of all the current and
future implementations of "ISubClass1 ".
2) Do a casting after "cm.SubClass1Va lues[0]" but then I have to write
separate indexers "SubClass2Index er" for each implementation of
"ISubClass1 ".
QUESTION:
How can I solve the shortcomings in the above solutions? Or in general
how is this best handled?
CODE:
using System;
using System.Collecti ons.Generic;
using System.Text;
namespace testProj
{
class Program
{
static void Main(string[] args)
{
MainClass cm = new MainClass();
cm.SubClass1Val ues[0].SubClass2Value s[0].ToString();
}
}
//CLASSES
public class MainClass
{
private SubClass1Indexe r m_subClass1Inde xer;
protected internal List<ISubClass1 m_subClass1List ; //
SubClass1Indexe r needs access to this.
public SubClass1Indexe r SubClass1Values
{
get { return m_subClass1Inde xer; }
}
}
public class SubClass1 : ISubClass1
{
private SubClass2Indexe r m_subClass2Inde xer;
protected internal List<ISubClass2 m_subClass2List ; //
SubClass2Indexe r needs access to this.
public SubClass2Indexe r SubClass2Values
{
get { return m_subClass2Inde xer; }
}
}
//INTERFACES
public interface ISubClass1
{
//!!! If the following would be possible then in
SubClass2Indexe r
// I would not have to make the function 'this[]' be aware of
all
// the ISubClass1 implementations .
//protected internal List<ISubClassm _subClass2List;
SubClass2Indexe r SubClass2Values { get; }
}
public interface ISubClass2
{
}
//INDEXERS
public class SubClass1Indexe r
{
private readonly MainClass m_subClass1Owne r;
public SubClass1Indexe r(MainClass seriesOwner)
{
m_subClass1Owne r = seriesOwner;
}
public ISubClass1 this[Int32 index]
{
get {
return m_subClass1Owne r.m_subClass1Li st[index];
}
}
}
public class SubClass2Indexe r
{
private readonly ISubClass1 m_subClass2Owne r;
public SubClass2Indexe r(ISubClass1 subClass2Owner)
{
m_subClass2Owne r = subClass2Owner;
}
public ISubClass2 this[Int32 index]
{
//The command commented out would be possible if one could
// define a field in an interface. Now I'll need a switch
// to handle all the IClass1 implementations . So I can't
just
// add a new implementation without adjusting this
function.
//get { return m_subClass2Owne r.m_subClass2Li st[index]; }
get { return
((SubClass1)m_s ubClass2Owner). m_subClass2List[index]; }
}
}
} 2 1982
Your structure is confusing which means there may be a simpler design.
However, I think you should be able to solve the issue by giving
SubClass1Indexe r a constructor that took a List<ISubClass1 rather than a
MainClass.
Post again if this doesnt work out.
--
Ciaran O''Donnell http://wannabedeveloper.spaces.live.com
"hu*******@yaho o.com" wrote:
SITUATION:
I have a class "MainClass" that has an indexer "SubClass1Index er".
This indexer returns an instance that implements a particular
interface "ISubClass1 ". This interface defines another indexer
"SubClass2Index er". Bellow is some code with comments. It should
compile.
PROBLEM:
I would like to write something like this:
MainClass cm = new MainClass();
cm.SubClass1Val ues[0].SubClass2Value s[0].ToString();
Note that "SubClass2Index er" needs access to an internal field of
"SubClass1" . This only seems to be possible if a field is allowed in
an interface, i.e. ISubClass1. That is not the case, though.
NONE IDEAL SOLUTIONS:
1) Make "this[]" in SubClass2Indexe r aware of all the current and
future implementations of "ISubClass1 ".
2) Do a casting after "cm.SubClass1Va lues[0]" but then I have to write
separate indexers "SubClass2Index er" for each implementation of
"ISubClass1 ".
QUESTION:
How can I solve the shortcomings in the above solutions? Or in general
how is this best handled?
CODE:
using System;
using System.Collecti ons.Generic;
using System.Text;
namespace testProj
{
class Program
{
static void Main(string[] args)
{
MainClass cm = new MainClass();
cm.SubClass1Val ues[0].SubClass2Value s[0].ToString();
}
}
//CLASSES
public class MainClass
{
private SubClass1Indexe r m_subClass1Inde xer;
protected internal List<ISubClass1 m_subClass1List ; //
SubClass1Indexe r needs access to this.
public SubClass1Indexe r SubClass1Values
{
get { return m_subClass1Inde xer; }
}
}
public class SubClass1 : ISubClass1
{
private SubClass2Indexe r m_subClass2Inde xer;
protected internal List<ISubClass2 m_subClass2List ; //
SubClass2Indexe r needs access to this.
public SubClass2Indexe r SubClass2Values
{
get { return m_subClass2Inde xer; }
}
}
//INTERFACES
public interface ISubClass1
{
//!!! If the following would be possible then in
SubClass2Indexe r
// I would not have to make the function 'this[]' be aware of
all
// the ISubClass1 implementations .
//protected internal List<ISubClassm _subClass2List;
SubClass2Indexe r SubClass2Values { get; }
}
public interface ISubClass2
{
}
//INDEXERS
public class SubClass1Indexe r
{
private readonly MainClass m_subClass1Owne r;
public SubClass1Indexe r(MainClass seriesOwner)
{
m_subClass1Owne r = seriesOwner;
}
public ISubClass1 this[Int32 index]
{
get {
return m_subClass1Owne r.m_subClass1Li st[index];
}
}
}
public class SubClass2Indexe r
{
private readonly ISubClass1 m_subClass2Owne r;
public SubClass2Indexe r(ISubClass1 subClass2Owner)
{
m_subClass2Owne r = subClass2Owner;
}
public ISubClass2 this[Int32 index]
{
//The command commented out would be possible if one could
// define a field in an interface. Now I'll need a switch
// to handle all the IClass1 implementations . So I can't
just
// add a new implementation without adjusting this
function.
//get { return m_subClass2Owne r.m_subClass2Li st[index]; }
get { return
((SubClass1)m_s ubClass2Owner). m_subClass2List[index]; }
}
}
}
Ciaran,
That indeed seems to be a solution. The reason I was passing MainClass
to the ctr of SubClass1Indexe r is because samples from MSDN and
CodeProject both did it this way. See here: http://msdn.microsoft.com/library/de...esTutorial.asp
Class WordCollection is the indexer and it's constructor takes the
parent class Document. MSDN says: "For each "indexed property," you
define a nested class, which contains a reference back to the main
class instance."
Is there a reason why most people do it this way and not the way you
suggested (which seems to work better for me)? This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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Vote for this idea if you like it here:
http://lab.msdn.microsoft.com/productfeedback/viewfeedback.aspx?feedbackid=5fee280d-085e-4fe2-af35-254fbbe96ee9
-----------------------------------------------------------------------------
This is a consortium of ideas from another thread on topic
-----------------------------------------------------------------------------
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