You can create an ordered collection of values in an OCL or EAL expression with Sequence{...}; use it when the order in which values are processed matters.
Create a Sequence
A Sequence is an ordered collection. Write Sequence, followed by values enclosed in curly braces.
Sequence{value1, value2, value3}
For example, this expression creates a Sequence of three strings in the stated order:
Sequence{'String', 'EmailAddress', 'PhoneNumber'}
Use a Sequence when you need a fixed list of values for an expression or iteration and want the list to retain its order.
Create a range of integers
Use a range inside a Sequence to create consecutive integers. The following expression creates the integers from 0 through 20:
Sequence{0..20}
This is useful when you need numbers for iteration or numbering. For example, iterate over the values in the range with collect:
Sequence{0..20}->collect(i | DoSomethingWithAnInt(i))
In this example, i is each integer in the Sequence, processed in order from 0 to 20.
Create a Sequence of strings
You can place string literals in a Sequence:
Sequence{'String', 'EmailAddress'}
This is useful when you want to process a known set of labels or values in a defined order. For an example that builds a dynamic collection of strings and converts it to comma-separated text, see Documentation:Collection of strings.
Choose the right collection literal
Use the collection type that expresses the behavior your expression needs.
| Collection type | Use it when | Example |
|---|---|---|
Sequence{...}
|
Element order matters. A Sequence is ordered and may contain duplicates. | Sequence{'First', 'Second', 'Third'}
|
Set{...}
|
You need unique values. A Set contains no duplicates. | Set{14, 22, 12}
|
Bag{...}
|
You need a collection that can contain duplicates, without choosing Sequence for ordering. | Bag{14, 22, 14}
|
Do not use a Set when repeated values are significant, because a Set contains no duplicates. Choose Sequence{...} for an ordered list, including a numeric range.
Related Sequence operations
Sequence{...} creates a new collection literal. To convert an existing value or collection to a Sequence, use asSequence(). To return a new Sequence with an item at the end, use append(); it does not change the source collection.