From: James Harrison <oscartheduck@...>
Date: 2010-08-02T22:54:04+09:00
Subject: Re: Iteration through File.file? misses entries for which  File.file?(entry) == true

If you're going to write an email and be wrong, be wrong on every point, that's what I was always taught and I'm sticking by it goddamit!

On Aug 2, 2010, at 7:28 AM 8/2/10, Brian Candler wrote:

> James Harrison wrote:
>> The symbolic constant for truth is True, not true.
> 
> That is incorrect, as 5 seconds with irb will show you.
> 
> $ irb --simple-prompt
>>> true
> => true
>>> True
> NameError: uninitialized constant True
>  from (irb):2
> 
> (You may have been thinking of TrueClass and FalseClass, perhaps?)

You're 100% correct. Total brainfart.


> 
>> In either case, because File.file? returns either True or False, you can 
>> drop the comparison:
> 
> It returns true or false, but yes the comparison can be removed.


> 
>> If this is truly a method in an object, though, bear in mind scoping 
>> issues. pwdFiles is only available inside this method definition. When 
>> you declare it in your intialize statement, prepend with a 
>> scope-changing symbol. The most common in this case is @
>> 
>> def initialize
>>    #will contain all file entries in the directory
>>    @pwdFiles = []
>> end
> 
> @ is not a "scope changing symbol". @pwdFiles is an instance variable of 
> the object, whereas pwdFiles is a local variable. They are completely 
> different concepts.
> 
> Since the OP wanted to return the value from the getFiles method, and 
> not set any instance variables in the object, then a local variable is 
> appropriate here.



In future, I'll have to stop myself whenever the thought "that mightn't be the right word" crops through my head. I figured it'd be close enough to get the idea across, but given that a symbol is actually a language construct I should've taken a few more seconds out.


In either case, you've hit something that interests me. Conceptually, I'd understood that the difference between an @-prepended variable and a non-@-prepended variable is that the former is global to the object, so it's not impacted by the change in scope introduced by defining a method inside the object. So I figured that describing the @ character as changing the internal scope of a variable from local to global inside the object wouldn't be entirely missing the mark. But it's possible I'm missing something.


Thanks for the clarifications and corrections, dude. 

Best

James