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)");
          }
        }

Using Tuples in MDriven Designer

Explanation 1

Tuples in OCL consist of Parts, and the results are accessed either as a part of the result if Part is derived or computed, or as an object type.

To get Category Sales on different dates:

Tuple Parts (How to access the data)	Description
Part1	Product Category is accessed with the name .Category instead of .Part1 since it is a known Type and is not derived.
Part2	The total quantity sold is accessed as .Part2 since it is derived.
Part3	Date of Sale is accessed as .DateAdded instead of .Part3 since it is a known Type and is not derived.

Explanation 2

To get Product Sales and their percentage of total Sales:

Tuple Parts (How to access the data)	Description
Part1	Product name in lowercase is accessed with the name .Part1 instead of .Name since it is derived.
Part2	The total quantity sold is accessed as .Part2 since it is derived.
Part3	Sale Percentage of Total Sales is accessed with the name .Part3 since it is derived.

See also: PSEvalTuples, SQLPassthrough

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