Documentation:Tuple

What is it

Tuple is a fancy word for something “taped together from bits and pieces of other stuff”.

Usage

This is very useful when it comes to building result sets that are not necessarily something that exists in your model - like sums or collecting names and addresses together even if they are stored in different classes. This is similar to an Anonymous type

Tuples are what an SQL server returns when you omit the " * " and write explicit stuff in the select part. In fact, the columns in the select part are the tuple definition as far as the SQL server is concerned.

OCL operators that create tuples are:

• GroupBy
• Collect

Example:

IElement elem = ocl.Evaluate(“Class1.allinstances.class2.class3->groupby(x|x.Attribute1)”);

What do I get back? A Tuple

The tuple consists of a type with a generated name and specific properties. The properties are Attribute1 and List.

Using tuples in CodeDress or C# in general

The code below shows how to access the tuple result in code:

        var onememtuple = (memoryresult[0] as ITuple);
        var onePSCase1tuple = (resultFromSQL92Joins[0] as ITuple);
        var onePSCase2tuple = (resultFromNormalJoins[0] as ITuple);
        for (int i = 0; i < onememtuple.Properties.Count; i++)
        {
          var p = onememtuple.Properties[i];
          var pPS1 = onePSCase1tuple.Properties[i];
          var pPS2 = onePSCase2tuple.Properties[i];
          if (p.AsObject != null)
          {
            Assert.IsTrue(p.AsObject.Equals(pPS1.AsObject), p.StructuralFeature.Name + " differs (sql92joins=true)");
            Assert.IsTrue(p.AsObject.Equals(pPS2.AsObject), p.StructuralFeature.Name + " differs (sql92joins=false)");
          }
        }

See also PSEvalTuples, SQLPassthrough