NAME

@dynamic_cast - Safely cast an object to a different type at runtime

SYNOPSIS

@dynamic_cast<CLASS-NAME[*]> {INPUT}

DESCRIPTION

The @dynamic_cast directive is used to safely cast an object to a different type at runtime.

The output of the @dynamic_cast directive will be either:

• An exact copy of INPUT if the input is a valid pointer to an object which can be safely cast to the specified type.
• @nullptr otherwise.

EXAMPLE

@Object obj

@Object* castedObj=@dynamic_cast<Object> &@obj # Successful cast of obj to Object pointer

@castedObj=@dynamic_cast<Object> "Hello, world!" # Failed cast, returns @nullptr

shell_variable=@dynamic_cast<Object*> &@obj # Successful cast, pointer stored in $shell_variable

@UnrelatedObject unrelatedObj

echo @dynamic_cast<Object> &@unrelatedObj # Failed cast, echoes @nullptr

NOTES

The input may be any rvalue at all, including a pointer to an object, a call to a method, a simple string, a supershell/subshell, etc. Of course, in most cases, the input should be a pointer to an object.

The @dynamic_cast directive is most useful when the type of the object is not known at compile time, or when the object may be of a different type than expected.

You can safely verify that a cast was successful by checking if the result is @nullptr. If it is not, you can safely use the result as a pointer to the specified type.

@DerivedClass derived_object
@BaseClass* myPointer=@dynamic_cast<BaseClass> &@derived_object

if [[ @myPointer == @nullptr ]]; then
	echo "The cast is invalid"
else
	echo "All OK!"
fi

SEE ALSO

• bpp-pointers(3) for more information on pointers
• bpp-classes(3) for more information on classes