How do I make a class iterable?

Question

This is my class

public class csWordSimilarity
{
    public int irColumn1 = 0;
    public int irColumn2 = 0;
    public int irColumn3 = 0;
    public int irColumn4 = 0;
    public int irColumn5 = 0;
}

I want to make that class iterable to be used like the way below

foreach (int irVal in myVarWordSimilarity)
{

}

myVarWordSimilarity is csWordSimilarity type. So I want to iterate all public int variables. How do I need to modify csWordSimilarity class for making it iterable like the way above.

Is there a reason why you would not use `List`? If yes, then look at implementing IEnumerable. — Davin Tryon, Feb 26 '12 at 16:58
Reference : [How to use foreach loop with custom objects](http://stackoverflow.com/a/348977/1004522). Go through this and it will also help you understand the usage whenever you want. — Ebad Masood, Feb 26 '12 at 17:03

score 39 · Accepted Answer · edited Dec 07 '18 at 11:53

39

You can implement IEnumerable and have the GetEnumerator override return an "iterator" over the variables using the yield statement

class csWordSimilarity : IEnumerable<int>
{
    private int _var1 = 1;
    private int _var2 = 1;
    private int _var3 = 1;
    private int _var4 = 1;

    public IEnumerator<int> GetEnumerator()
    {
        yield return _var1;
        yield return _var2;
        yield return _var3;
        yield return _var4;
    }

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

edited Dec 07 '18 at 11:53

Mizux

8,222
7
32
48

answered Feb 26 '12 at 16:58

edvaldig

2,301
16
17

1

thanks a lot for answer though your solution giving error "Using the generic type 'System.Collections.Generic.IEnumerator' requires 1 type arguments" – Furkan Gözükara Feb 26 '12 at 17:21
1

Which version of .NET are you using? I can't think of a way to replicate that error since .NET 4 allows you to omit the template type definition so it will become an IEnumerable – edvaldig Feb 26 '12 at 20:17
1

it tells me that IEnumerable requires 1 type arguments when I try this – mcmillab Apr 12 '18 at 00:03
1

this is amazing. – orion elenzil Dec 14 '20 at 22:05

score 7 · Answer 2 · edited Dec 07 '18 at 12:54

7

Implement IEnumerable. See Using Iterators (C# Programming Guide)

In your case you could just use the built-in iterator of a List like so:

using System;
using System.Collections.Generic;

class csWordSimilarity : IEnumerable<int> {
    public int irColumn1 = 0;
    public int irColumn2 = 0;
    public int irColumn3 = 0;
    public int irColumn4 = 0;
    public int irColumn5 = 0;

    public IEnumerator<int> GetEnumerator() {
        return (new List<int>() { 
            irColumn1, irColumn2, irColumn3, irColumn4, irColumn5 
        }).GetEnumerator();
    }
    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() {
        return GetEnumerator();
    }
}

edited Dec 07 '18 at 12:54

Mizux

8,222
7
32
48

answered Feb 26 '12 at 16:58

Joshua Honig

12,925
8
53
75

2

There is a considerable overhead in instantiating a new List instance for the sole purpose of returning an enumerator of it, the yield statement simplifies this and is more optimal. – edvaldig Feb 26 '12 at 17:06
@edvaldig I think it's a matter of preference. If you're going to call this millions of times, then yes use the direct `yield`. Otherwise I prefer using BCL classes and especially `List` where convenient. – Joshua Honig Feb 26 '12 at 17:09

How do I make a class iterable?

2 Answers2

Linked

Related