Compare two class objects values "Greater Than"

Question

I have two classes which contain the 12 months as object names and its values are decimal. I have to check whether class A object greater than class B object.

Class A
{
   decimal Jan;    
   decimal Feb;    
   decimal Mar;
}

Class B
{
   decimal Jan;    
   decimal Feb;    
   decimal Mar;
}

Right now, i am using if loop for all the object to check the validation.

if(A.Jan > B.Jan)
{
  return false;
}
else if(A.Feb > B.Feb)
{
  return false;
}
else if(A.Mar > B.Mar)
{
  return false;
}

Is there any mechanism to simplify this logic.

Use an array of decimals to hold the 12 months' values, then just loop over the array and have a single `if` in the loop body? — Matthew Watson, Aug 24 '20 at 11:02
I don't know if this is due to simplification, but why do you need two different classes here? — Fildor, Aug 24 '20 at 11:04
Does this answer your question? [What are the basic rules and idioms for operator overloading?](https://stackoverflow.com/questions/4421706/what-are-the-basic-rules-and-idioms-for-operator-overloading) — Hogan, Aug 24 '20 at 11:26
@Fildor I have sampled here but in real time both are having different values and which needs to be compared. — Vignesh Kumar A, Aug 24 '20 at 11:29
@VigneshKumarA That would be a reason to have two _instances_. But you define two different _types_ ... but anyway. I take it as it is. — Fildor, Aug 24 '20 at 11:31
Will the two classes have the same property names? and in the same order? — Sowmyadhar Gourishetty, Aug 24 '20 at 11:40
Implement IComparable/ IComparer on the classes and compare one with the other and override Compare method. This way you can compare one object with another. — JaisG, Aug 24 '20 at 12:18

score 1 · Answer 1 · edited Aug 24 '20 at 12:21

Perhaps implement a function in the two classes that returns a collection of the month values. You can then compare them one by one.

void Main()
{
    var a = new A() { Jan = 1, Feb = 1, Mar = 5 };
    var b = new B() { Jan = 1, Feb = 1, Mar = 3 };

    Compare(a, b).Dump();
}

private bool Compare(A a, B b)
{
    var ae = a.GetMonthValues().GetEnumerator();
    var be = b.GetMonthValues().GetEnumerator();
    while (ae.MoveNext() & be.MoveNext())
    {
        if (ae.Current > be.Current)
            return false;
    }
    return true;
}

class A
{
    public decimal Jan;
    public decimal Feb;
    public decimal Mar;

    public IEnumerable<decimal> GetMonthValues() => new[] { Jan, Feb, Mar };
}

class B
{
    public decimal Jan;
    public decimal Feb;
    public decimal Mar;

    public IEnumerable<decimal> GetMonthValues() => new[] { Jan, Feb, Mar };
}

You can also extract an interface with the GetMonthValues function and let both classes implement that. (and the month properties if desired)

It would all be better if the storage of the month data was encapsulated in an object right? — Hogan, Aug 24 '20 at 12:31

Hogan · Answer 2 · 2020-08-24T12:35:59.137

You could use operator overloading to do this -- like this:

inline bool operator< (const A& lhs, const B& rhs)
{
  /* do actual comparison */ 
}

see this question and answer

What are the basic rules and idioms for operator overloading?

You could also use the following pattern with an interface :

interface ExtractDate<T>
{
  decimal getDate(integer which);
}


Class A : ExtractDate<A>
{
   decimal getDate(integer which)
   {
     switch (which)
     {
       case 1 : return this.Jan; break;
       case 2 : return this.Feb; break;
       case 3 : return this.Mar; break;
     }
   }
   decimal Jan;    decimal Feb;    decimal Mar;
}

Class B : ExtractDate<B>
{
   decimal getDate(integer which)
   {
     switch (which)
     {
       case 1 : return this.Jan; break;
       case 2 : return this.Feb; break;
       case 3 : return this.Mar; break;
     }
   }
  decimal Jan;    decimal Feb;    decimal Mar;
}

Then you can say

 if(A.getDate(1) > B.getDate(1))
 {
    return false;
 }
 //etc

If it was me this seems like a lot of work -- I myself would make a object called DateInfo and have both objects implement that object (it is the same in both object) and then compare objects of the same type -- which is much easier.

Thsnka for your answer but again the code which i need to write for all the object right? which i wanted to overcome by simply passing the class and it should found is there values greater and returtn true. — Vignesh Kumar A, Aug 24 '20 at 12:04
Why `T obj` in `getDate` and why `T` at all in the interface? — Magnus, Aug 24 '20 at 12:31

score 0 · Answer 3 · answered Aug 24 '20 at 12:38

You can combine class A and B into one class and then overload the compare operator, like this:

Class Year
{
   decimal Jan;    
   decimal Feb;    
   decimal Mar;
   
   private List<decimal> Months = new List<decimal> {Jan, Feb, Mar}

   public static bool operator<(Year a, Year b)
   {
      for(int i = 0; i < Months.Count; i++)
      {
          if(a.Months[i]<b.Months[i]) return true;
      }
      return true;
   }

   public static bool operator>(Year a, Year b)
   {
      for(int i = 0; i < Months.Count; i++)
      {
          if(a.Months[i]>b.Months[i]) return true;
      }
      return true;
   }
}

Also I introduced a list for the months so you do not have to if-else them separately

Compare two class objects values "Greater Than"

3 Answers3