uninitialized stream (IOError)

[Glen Holcomb]

So I'm getting an unexpected IOError in my code.

class ConfigStub < File
def initialize(location)
unless filename =3D location.gsub("/", "_")
raise ArgumentError, INVALID_LOCATION_FORMAT
end
@stub =3D File.open(CONFIG_PATH + filename, "w+") # This might need=
to
be more sophisticated depending on the rule
end # initialize
end # ConfigStub class

class Directive
def initialize(location)
@sanity_checker =3D SanityChecker.new()
@config_stub =3D ConfigStub.new(location)
@directive =3D ["<Location #{location}>"]

@config_stub.each do |line|
@directive << line
end
end # initialize

 

[Brian Candler]

You're trying to mix subclassing and delegation.

That is: your object is a subclass of File, and therefore an instance of
ConfigStub *is* a File. However you are also opening another File and
storing it in the instance variable @stub, and therefore it *has* a File
as well.

Choose one or the other. In my experience, delegation is the most
flexible and understandable approach, and although it needs some setting
up it ends up being simplest in the long run.

You can delegate manually:

class ConfigStub
def initialize(location)
@stub = File.open(...)
end
def each(*args,&blk)
@stub.each(*args,&blk)
end
def read(*args)
@stub.read(*args)
end
... etc, and/or
def method_missing(*args,&blk)
@stub.__send__(*args,&blk)
end
end

or use a wrapped up version of this - check out SimpleDelegator in
delegate.rb in the standard library.

If you want to subclass File, then you'll need to ensure you call its
initialize method. Probably something like this (untested):

class ConfigStub < File
def initialize(location)
..
super(CONFIG_PATH + filename, "w+") # in the superclass
end
end

But subclassing core classes can get you tied up in knots if you're not
careful (as I think you've already discovered)

Regards,

Brian.

 

[Glen Holcomb]

Thanks Brian.

You're trying to mix subclassing and delegation.

That is: your object is a subclass of File, and therefore an instance of
ConfigStub *is* a File. However you are also opening another File and
storing it in the instance variable @stub, and therefore it *has* a File
as well.

Choose one or the other. In my experience, delegation is the most
flexible and understandable approach, and although it needs some setting
up it ends up being simplest in the long run.

You can delegate manually:

class ConfigStub
def initialize(location)
@stub =3D File.open(...)
end
def each(*args,&blk)
@stub.each(*args,&blk)
end
def read(*args)
@stub.read(*args)
end
... etc, and/or
def method_missing(*args,&blk)
@stub.__send__(*args,&blk)
end
end

or use a wrapped up version of this - check out SimpleDelegator in
delegate.rb in the standard library.

If you want to subclass File, then you'll need to ensure you call its
initialize method. Probably something like this (untested):

class ConfigStub < File
def initialize(location)
..
super(CONFIG_PATH + filename, "w+") # in the superclass
end
end

But subclassing core classes can get you tied up in knots if you're not
careful (as I think you've already discovered)

Regards,

Brian.

--=20
"Hey brother Christian with your high and mighty errand, Your actions speak
so loud, I can=92t hear a word you=92re saying."

-Greg Graffin (Bad Religion)