Is there another library like this? I would love it if it were just
standard methods on Object.
I find this very useful and ‘require’ it into all code I write. Just
helps me mop up those problems that static type checking would have
found for me…
Heres a typical usage, create an object and initialize it with
stuff. Only much later when you invoke the methods on the object do
you find you initialized it with the wrong stuff.
Got the parameter order wrong or something. But then the bug isn’t on
the backtrace. So put when you initialize your instance variables you
can type check’em like so…
eg.
class MyObject
def initialize( _name, _drawable, _theme)
@name = _name.static_type_check String
@drawable = _drawable.polymorphic_type_check Drawable
@theme = _theme.quacks_like :border_color, :fill_colour
end
…
end
Abstract base class for all the type check exceptions
class TypeCheckException < Exception
end
This exception is thrown in event of a method being invoked with an
object of the wrong duck type.
class DuckTypingException < TypeCheckException
end
This exception is thrown in event of a method being invoked with a
parameter of of the wrong static type.
class StaticTypeException < TypeCheckException
end
This exception is thrown in event of a method being invoked with a
parameter of of the wrong polymorphic type.
class PolymorphicTypeException < TypeCheckException
end
class Object
# Raise a DuckTypingException unless the object responds to all
these symbols.
def quacks_like( *symbols)
symbols.each do |symbol|
raise DuckTypingException, “Duck typing error, expected this
object to respond to :#{symbol}, but found class
#{self.class}\n\t\t#{symbol.inspect}” unless
respond_to? symbol
end
self
end
def static_type_check_boolean
raise StaticTypeException, "Static type check error, expected
object to be a boolean, found ‘#{self.class}’
\t\t#{self.inspect}" unless
(self.class == TrueClass) ||
(self.class == FalseClass) ||
(self.class == NilClass)
self
end
def static_type_check( klass)
raise StaticTypeException, "Static type check error, expected
object to be exactly class ‘#{klass}’, found
‘#{self.class}’\n\t\t#{self.inspect}" unless
self.class == klass
self
end
def static_type_check_each( klass)
each do |object|
object.static_type_check klass
end
self
end
def polymorphic_type_check_each( klass)
each do |object|
object.polymorphic_type_check klass
end
self
end
def polymorphic_type_check( klass)
raise PolymorphicTypeException, "Polymorphic type check error,
expected object to be a kind of ‘#{klass}’, found
‘#{self.class}’\n\t\t#{self.inspect}" unless
self.kind_of? klass
self
end
end
John C. Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : [email protected]
New Zealand
I think it all depends on exactly what you’re doing with
An