class Exception { ... }
All exceptions that are placed into the $! variable (or into $_ in CATCH blocks) inherit from Exception. When you call die or fail with a non-Exception argument, it is wrapped into an X::AdHoc object, which also inherits from Exception.
User-defined exception classes should inherit from Exception too, and define at least a method message.
class X::YourApp::SomeError is Exception {
method message() {
"A YourApp-Specific error occurred: out of coffee!";
}
}
method message(Exception:D:) returns Str:D
This is a stub that must be overwritten by subclasses, and should return the exception message.
Special care should be taken that this method does not produce an exception itself.
method backtrace(Exception:D:) returns Backtrace:D
Returns the backtrace associated with the exception. Only makes sense on exceptions that have been thrown at least once.
method throw(Exception:D:)
Throws the exception.
method rethrow(Exception:D:)
Rethrows an exception that has already been thrown at least once. This is different from throw in that it preserves the original backtrace.
method fail(Exception:D:)
Same as fail $exception; i.e., it exits the calling Routine and returns the exception wrapped in a Failure object.
multi method gist(Exception:D:)
Returns whatever the exception printer should produce for this exception. The default implementation returns message and backtrace separated by a newline.
Full-size type graph image as SVGException inherits from class Any, which provides the following methods:
multi method ACCEPTS(Any:D: Mu $other)
Returns True if $other === self (ie it checks object identity).
Interprets the invocant as a list and creates an any-Junction from it.
Interprets the invocant as a list and creates an all-Junction from it.
Interprets the invocant as a list and creates an one-Junction from it.
Interprets the invocant as a list and creates an none-Junction from it.
Exception inherits from class Mu, which provides the following methods:
multi sub defined(Mu) returns Bool:D multi method defined() returns Bool:D
Returns False on the type object, and True otherwise.
multi sub Bool(Mu) returns Bool:D multi method Bool() returns Bool:D
Returns False on the type object, and True otherwise.
multi method Str() returns Str
Returns a string representation of the invocant, intended to be machine readable.
multi sub gist(Mu) returns Str multi method gist() returns Str
Returns a string representation of the invocant, optimized for fast recognition by humans.
The default gist method in Mu re-dispatches to the perl method, but many built-in classes override it to something more specific.
multi sub perl(Mu) returns Str multi method perl() returns Str
Returns a Perlish representation of the object (i.e., can usually be reparsed to regenerate the object).
method clone(*%twiddles)
Creates a shallow clone of the invocant. If named arguments are passed to it, their values are used in every place where an attribute name matches the name of a named argument.
multi method new(*%attrinit)
Default method for constructing (create + initialize) new objects of a class. This method expects only named arguments which are then used to initialize attributes with accessors of the same name.
Classes may provide their own new method to override this default.
method bless(Mu $candidate, *%attrinit) returns Mu:D
Lower-level object construction method than new.
If you pass a Whatever as a candidate, it creates a new object of the same type as the invocant, and then uses the named arguments to initialize attributes.
If you pass something other than a Whatever object as a candidate, it simply does the attribute initialization on the $candidate.
In both cases, the object with the attributes initialized is returned.
You can use this method when writing custom constructors:
class Point {
has $.x;
has $.y;
multi method new($x, $y) {
self.bless(:$x, :$y);
}
}
my $p = Point.new(-1, 1);
(Though each time you write a custom constructor, remember that it makes subclassing harder).
method CREATE() returns Mu:D
Allocates a new object of the same type as the invocant, without initializating any attributes.
multi method print() returns Bool:D
Prints value to $*OUT after stringification using .Str method without newline at end.
multi method say() returns Bool:D
Prints value to $*OUT after stringification using .gist method with newline at end.
multi method ACCEPTS(Mu:U: $other)
Performs a type check. Returns True if $other conforms to the invocant (which is always a type object or failure).
This is the method that is triggered on smart-matching against type objects, for example in if $var ~~ Int { ... }.
multi method WHICH() returns ObjAt:D
Returns an object of type ObjAt which uniquely identifies the object. Value types override this method which makes sure that two equivalent objects return the same return value from WHICH.