OCL operators are used to define constraints and operations on objects in an object-oriented programming language like Java, C++, or C#. They can be used in OCL expressions to specify constraints on objects or to perform operations on object properties.

For example, let's say we have a class called "Person" with properties like "name," "age," and "gender." We can use OCL operators to define constraints on the properties of the "Person" class. Here are some examples:

1. To define a constraint that ensures that the "age" property of a "Person" object is greater than or equal to 18, we can use the greater than or equal to (>=) operator as follows: context Person inv: self.age >= 18
2. To define a constraint that ensures that the "gender" property of a "Person" object is either "Male" or "Female," we can use the OR (||) operator as follows: context Person inv: self.gender = 'Male' or self.gender = 'Female'
3. To define a constraint that ensures that the "name" property of a "Person" object starts with an uppercase letter, we can use the dot notation (.) and the regular expression operator (matches) as follows: context Person inv: self.name.matches('^[A-Z]')

In addition to defining constraints, OCL operators can also be used to perform operations on object properties. For example, we can use the sum() operator to calculate the sum of all the elements in a collection property of a "Person" object as follows: context Person inv: self.salary.sum() < 100000

OCL operators make it easy to write correct and maintainable object-oriented programs.

Examples of OCL Operators

Title	Content

General Operators

Collection Operators

String Operators

Number Operators

Boolean Operators

General Operators

To find all available operators, you can open the OCL-Editor and type in a class:

Operators	Description
allInstances	All the objects of the class
allinstancesAtTime	All the currently loaded instances
allLoadedObjects	All objects currently in memory, excluding deleted objects
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
ASCII
associationEnds	Returns a collection of strings with association names for the class
associationEndsWithType	Returns a collection of strings with association names and type information for the class
asString	The string representation of the class – the asString operation is available on everything
asTaJson	Returns a json string defined by the ViewModel
atTime	Gives the read-only representation of a versioned object as it was at time X.
Attributes	Meta information about what attributes the class has
BigEndianUnicode
brokenConstraints	Returns a collection of the names of broken constraints for the class and object.
canAccess	Check ViewModels Access expression for root
Constraints	Meta information on what constraints the class has
count	Returns how many times the object is in the collection self.
Default
Empty
emptylist	Returns an empty list typed to hold objects of the class
existing	The existing operator returns true if the object hasn't been deleted.
externalId	Returns the external ID for the object operated on.
format
IsDirty	Returns true if the objects have been changed since the last save.
IsNew	IsNew operator returns true if the object has never been saved to the database.
isDirtyMember	Called on a class attribute to check if this attribute has changes pending to be saved.
isNull	Returns true if the value is null (not assigned any value).
maxValue	Gets the maximum value in a collection of values
minValue	Gets the minimum value in a collection of values
nullValue	A typed null value
objectFromExternalId	An external identity will be resolved to the object
oclAsType	The type of the class
oclGetStates	Gets a list of the objects all state machines currently state as strings.
oclIsInvalid	Returns true if self is equal to *invalid*.
oclIsKindOf	This is to if a class is a subclass or as the class itself and not unrelated
oclIsTypeOf	Returns true if
OnCreate	Is often called when a new object has been created.
OnUpdate	Is called just before the object is saved to the database.
oclIsUndefined	Returns true if self is equal to invalid or null.
OclType	When used on an object, you get the type of the object.
random
safeCast
sqlpassthrough	Calls a stored procedure
sqlpassthroughobjects	Return a primary key of SomeClass. This can be combined with other Ocl-PS via ->intersection or union.
superTypes	Returns the set of all direct supertypes of the type.
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

Collection Operators

Once you have a collection of objects, there are certain operators applicable to them.

See this page for examples on collection operators.

Again, you can use the OCL-Editor to see what they are:

Operators	Description
->append	Add another object last
->asBag	Returns a Bag containing all elements of self.
->asSequence	Returns a Sequence containing all elements of self. Element ordering is preserved when possible.
->asSet	Returns a Set containing all elements of self.
->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	Returns a collection containing the result of applying expr on all elements contained in self.
->count	Count how many meet a certain criteria
->dictionary	Efficiently looks up values
->difference	The difference between 2 collections
->excluding	The collection except for this single object
->exists	Returns true if at least one element in self validates the condition expr, false otherwise.
->filterOnType	Only keep the ones of a certain type
->first	Return the first object
->forAll	Returns true if all the elements contained in self validate the condition expr, false otherwise.
->groupBy	Build a collection of tuples grouped by some aspect
->includes	Does the collection include the object
->includesAll	Does the collection include the whole other collection
->including	Returns the list with the element in the parameter included.
->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
->notEmpty	Returns true if self contains at least one element, false otherwise.
->reject	Returns a collection with all elements of self except for those who validate the OclExpression expr.
->select	Returns a collection with all elements of self that validate the OclExpression expr.
->size	Returns the number of elements contained in self.
->sum	Returns the sum of all elements contained in self if they support the '+' operation.
->last	Returns the last object in the collection
->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	Returns an OrderedSet containing object followed by all elements of self.
->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

String Operators

Operators	Description
Escape codes	Escape (special) characters used in OCL
StringToAnsiBase64	Convert a string to an ANSI (1252) and as a base64 string
StringToEncodedBase64	Convert a string to a specific encoding and as a base64 string. For example Western European (ISO) Codepage 28591
size () : Integer	Returns the number of characters composing self.
subString	Returns the substring of the string operated on. The substring starts at parameter 1 and ends at parameter 2. The counting is 1-based.
toInteger () : Integer	Returns self with all characters converted to lowercase.
toLower () : String	Returns self with all characters converted to lowercase.
toReal () : Real	Returns a Real of value equal to self, or |invalid| if self does not represent a real.
toUpper () : String	Returns self with all characters converted to uppercase.

Number Operators

In addition to the basic math functions (+, -, /, \*) are a number of advanced functions. Take note that *Number* denotes both *Integer* and *Real*, and they're substitutive unless otherwise specified.

Operators	Description
Number::abs () : Number	Returns the absolute value of self, self if it is already a positive number.
Number::floor () : Integer	Returns the integer part of self if it is a Real, self if it is an Integer.
Number::max ( r : Number ) : Number	Returns the greatest number between self and *r*.
Number::min ( r : Number ) : Number	Returns the lowest number between self and *r*.
Number::round () : Integer	Returns the nearest integer to self if it is a Real, self if it is an Integer.
Number::ieeereminder(r:Number):Integer	Reminder of division with r, ie modulus or mod or %
Integer::div ( i : Integer ) : Integer	Returns the integer quotient of the division of self by *i*.
Integer::mod ( i : Integer ) : Integer	Returns the integer remainder of the division of self by *i*.

Boolean Operators

Operators	Description
And	And True False Invalid True true false true False false false false Invalid invalid false invalid
Implies	Implies True False Invalid True true false invalid False true true true Invalid true invalid invalid
Or	Or True False Invalid True true true true False true false invalid Invalid true invalid invalid
Not	Not Result True false False true Invalid invalid
Xor	Xor True False Invalid True false true invalid False true false invalid Invalid invalid invalid invalid

ViewModel Operators (on selfVM variable)

See page: SelfVM