OCLOperators allInstances
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|Filtering on Specialization is done with an operator SafeCast. This is null safe so for all objects that do not fit the profile the expression returns false
|Filtering on Specialization is done with an operator SafeCast. This is null safe so for all objects that do not fit the profile the expression returns false
|}
|}
To find all available you can open the OCL-Editor and type in a class:
[[File:Ocl-editor 1.png|frameless|433x433px]]
The operations listed do this:
{| class="wikitable"
!Operators
!Description
|-
|'''Allinstances'''
|All the objects of the class
|-
|'''allinstancesAtTime'''
|All the currently loaded instances
|-
|'''AllStates'''
|Meta information about available states in state machines the class may contain
|-
|'''allSubClasses'''
|Meta information on all the sub classes this class has
|-
|'''AllSuperTypes'''
|Meta information on all the super classes – in inheritance order the class has
|-
|'''associationEnds'''
|Meta information on all the associationEnds
|-
|'''Asstring'''
|The string representation of the class – the asString operation is available on everything
|-
|'''Attributes'''
|Meta information about what attributes the class has
|-
|'''Contraints'''
|Meta information on what constraints the class has
|-
|'''Emptylist'''
|Returns an empty list typed to hold objects of the class
|-
|'''IsDirtyMember'''
|
|-
|'''isNull'''
|
|-
|'''nullValue'''
|A typed null value
|-
|'''objectFromExternalId'''
|An external identity will be resolved to the object
|-
|'''oclAsType'''
|The type of the class
|-
|'''oclIsKindOf'''
|This is to if a class is a subclass or a the class itself and not unrelated
|-
|'''oclIsTypeOf'''
|Returns true if
|-
|'''oclSingleton'''
|Classes that implements the Singleton pattern – by setting IsSingleton=true – will return the singleton instance with this operator
|-
|'''OclType'''
|
|-
|'''safeCast'''
|
|-
|'''SuperTypes'''
|
|-
|'''TaggedValue'''
|Meta information on tagged values set in the class
|-
|'''TaggedValueOnFeature'''
|Meta information on Tagged values set on a named feature in the class
|-
|'''Typename'''
|The type name as a string
|-
|'''ViewModels'''
|A tuple with the ViewModels for this class a members
|}
Once you have a collection of objects there are certain operators that are applicable to it. Again you can use the OCL-Editor to see what they are:
[[File:Collection of objects operators.png|frameless|453x453px]]
{| class="wikitable"
!Operators
!Description
|-
| '''->append'''
|Add another object last
|-
| '''->asBag'''
|Collapses to one list
|-
| '''->asSequence'''
|Collapses to one list
|-
| '''->asset'''
|Remove doublets
|-
| '''->at'''
|Get the objects at X where the first index is 1
|-
| '''->at0'''
|Get the objects at X where the first index is 0
|-
| '''->collect'''
|Iterate over the collection and build a tuple result
|-
| '''->count'''
|Count how many meet a certain criteria
|-
| '''->difference'''
|The difference between 2 collections
|-
| '''->excluding'''
|The collection except this single object
|-
| '''->exists'''
|Are there any objects that fulfill the criteria
|-
| '''->filterOnType'''
|Only keep the ones of a certain type
|-
| '''->first'''
|Return the first object
|-
| '''->forAll'''
|Iterate all that fulfills the critera
|-
| '''->groupBy'''
|Build collection of tuples grouped by some aspect
|-
| '''->includes'''
|Does the collection include the object
|-
| '''->includesAll'''
|Does the collection include the whole other collection
|-
| '''->including'''
|
|-
| '''->IndexOf'''
|The 1 based index of an object in the collection possibly -1 if not existing
|-
| '''->indexOf0'''
|The 0 based index of an object in the collection possibly -1 if not existing
|-
| '''->intersection'''
|The intersection of two collections
|-
| '''->isEmpty'''
|Returns true if the collection is empty
|-
| '''->last'''
|Returns the last object in the collection
|-
| '''->notEmpty'''
|Returns true of the collection is not empty
|-
| '''->orderBy'''
|Sorts the collection on one or more properties
|-
| '''->orderDescending'''
|Sort the from biggest to smallest
|-
| '''->orderGeneric'''
|Sorts the list of properties with interchangeable sort order: (expr1, OclSortDirection::ascending, expr2, OclSortDirection::descending...)
|-
| '''->prepend'''
|Add an object in front of the list
|-
| '''->reject'''
|Returns the objects not matching the criteria
|-
| '''->select'''
|Returns the objects matching the criteria
|-
| '''->size'''
|Returns the number of elements in the collection
|-
|'''->subsequence'''
|Returns a smaller collection from a start to stop
|-
|'''->symmetricDifference'''
|The symmetric difference between the collections; ie all the objects in collection1 or collection2 but not in both
|-
| '''->union'''
|The set of objects in collection1 and objects in collection2
|}
One important aspect of OCL that is worth noting is that it expands lists of lists to just a list. An example in plain English; Thing.allinstances.Details – this will come back as a set of details that are all the details from all the Things. If OCL had not expanded lists automatically one could have expected a set of sets containing the details per thing. But this is not the case. The automatically expansion of lists of lists is sometime referred to as flattening of a collection – referring to the reduction of topology in the result.
==== Some OCL examples ====
{| class="wikitable"
!Examples
!Results
|-
|Bag{'5','1','2','2','3','4'}->ascommalist
|5, 1, 2, 2, 3, 4
|-
|Bag{'5','1','2','2','3','4'}- >union(Bag{'1','2','2','3','6'})->ascommalist
|5, 1, 2, 2, 3, 4, 6
|-
|Bag{'5','1','2','2','3','4'}- >union(Bag{'1','2','2','3','6'})->asset- >ascommalist
|5, 1, 2, 3, 4, 6
|-
|<nowiki>Bag{'5','1','2','2','3','4'}- >union(Bag{'1','2','2','3','6'})->asset- >orderby(a|a)->ascommalist</nowiki>
|1, 2, 3, 4, 5, 6
|-
|<nowiki>Bag{'5','1','2','2','3','4'}- >intersection(Bag{'1','2','2','3','6'})- >orderby(a|a)->ascommalist</nowiki>
|1, 2, 2, 3
|-
|<nowiki>Bag{'5','1','2','2','3','4'}- >Difference(Bag{'1','2','2','3','6'})->orderby(a|a)- >ascommalist</nowiki>
|4, 5
|-
|<nowiki>Bag{'5','1','2','2','3','4'}- >SymmetricDifference(Bag{'1','2','2','3','6'})- >orderby(a|a)->ascommalist</nowiki>
|4, 5, 6
|}
If you are in the context of a simple type like string, double, int, datetime or Boolean MDriven will expose the simple operations that are available in the .net Framework. Testing this in the OCL-Editor:

Revision as of 15:40, 13 August 2017

It is a common operator. To find all available you can open the OCL-Editor and type in a class:

Your model is central to all expression you will handle. We will use this model to for the examples:

Allinstances operator.png

Operators Description
Thing.allinstances Gives you a list of all Things
Things.allinstances->select(someInt>3) Only things with someInt bigger than 3
Thing.allinstances->select( (someInt>3) and (someInt<6)) Only things with someInt bigger than 3 but less than 6. Notice the extra parenthesis to or the Boolean expressions together
Things.allinstances->select(x|x.someInt>3) Here we introduce the loop variable x. We separate the definition of x from the usage of x with the pipe sign “|”. Loop variables are optional but if names are unique – but you will need to use them to give precision or to if you want to perform operations on the loop context itself.
Things.allinstances.Details Gives a list of all detail objects that are connected to a Thing. The Detail objects that float around without a Thing will not be in the list
Things.allinstances.Details.Attribute1 A list of nullable strings from the contents from the details attribute1. Note that OCL is null-tolerant – you do not need to check if the Details exists of not – the language handles null checks for you
SubClassThing1.allinstances.Details Inherited features of classes are directly accessible
Thing.allInstances- >select(x|x.safeCast(SubClassThing1). OnlyAvailableInSubClass='Hello') Filtering on Specialization is done with an operator SafeCast. This is null safe so for all objects that do not fit the profile the expression returns false
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