built-in predicate



create_object(Identifier, Relations, Directives, Clauses)

Creates a new, dynamic object. The word object is used here as a generic term. This predicate can be used to create new prototypes, instances, and classes. This predicate is often used as a primitive to implement high-level object creation methods.

Note that, when opting for runtime generated object identifiers, it’s possible to run out of identifiers when using a backend Prolog compiler with bounded integer support. The portable solution, when creating a large number of dynamic objects in long-running applications, is to recycle, whenever possible, the identifiers.

When creating a new dynamic parametric object, access to the object parameters must use the parameter/2 built-in execution context method.

Declared predicates (using scope clauses in the Directives argument) are implicitly declared also as dynamic.

When using Logtalk multi-threading features, predicates calling this built-in predicate may need to be declared synchronized in order to avoid race conditions.

Modes and number of proofs

create_object(?object_identifier, @list(object_relation), @list(object_directive), @list(clause)) - one


Relations, Directives, or Clauses is a variable:
Identifier is neither a variable nor a valid object identifier:
type_error(object_identifier, Identifier)
Identifier is already in use:
permission_error(modify, category, Identifier)
permission_error(modify, object, Identifier)
permission_error(modify, protocol, Identifier)
Relations is neither a variable nor a proper list:
type_error(list, Relations)
Repeated entity relation clause:
permission_error(repeat, entity_relation, implements/1)
permission_error(repeat, entity_relation, imports/1)
permission_error(repeat, entity_relation, extends/1)
permission_error(repeat, entity_relation, instantiates/1)
permission_error(repeat, entity_relation, specializes/1)
Directives is neither a variable nor a proper list:
type_error(list, Directives)
Clauses is neither a variable nor a proper list:
type_error(list, Clauses)


% create a stand-alone object (a prototype):
| ?- create_object(
         [int(0, zero)]

% create a prototype derived from a parent prototype:
| ?- create_object(

% create a class instance:
| ?- create_object(
         [name('Paulo Moura'), age(42)]

% create a subclass:
| ?- create_object(
         [public([propeller/2, fan/2])],

% create an object with an initialization goal:
| ?- create_object(
         [length(22), time(60)]

% create an object supporting dynamic predicate declarations:
| ?- create_object(
         [set_logtalk_flag(dynamic_declarations, allow)],