Why use tuples instead of objects?

The codebase where I work has an object called Pair where A and B are the types of the first and second values in the Pair. I find this object to be offensive, because it gets used instead of an object with clearly named members. So I find this:

List<Pair<Integer, Integer>> productIds = blah();
// snip many lines and method calls

void doSomething(Pair<Integer, Integer> id) {
  Integer productId = id.first();
  Integer quantity = id.second();
}

Instead of

class ProductsOrdered {
  int productId;
  int quantityOrdered;
  // accessor methods, etc
}

List<ProductsOrderded> productsOrdered = blah();

Many other uses of the Pair in the codebase are similarly bad-smelling.

I Googled tuples and they seem to be often misunderstood or used in dubious ways. Is there a convincing argument for or against their use? I can appreciate not wanting to create huge class hierarchies but are there realistic codebases where the class hierarchy would explode if tuples weren't used?

c++ tuples

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1 Answer

The code example has a few different smells:

Reinventing the wheel

There is already a tuple available in the framework; the KeyValuePair structure. This is used by the Dictionary class to store pairs, but you can use it anywhere it fits. (Not saying that it fits in this case...)

Making a square wheel

If you have a list of pairs it's better to use the KeyValuePair structure than a class with the same purpose, as it results in less memory allocations.

Hiding the intention

A class with properties clearly shows what the values mean, while a Pair<int,int> class doesn't tell you anything about what the values represent (only that they are probably related somehow). To make the code reasonably self explanatory with a list like that you would have to give the list a very desciptive name, like productIdAndQuantityPairs...

answered 2009-03-23T21:48:10.307

Why use tuples instead of objects?

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