We''ve heard the more knowledgeable of the community say that we should
invest some time into learning and understanding Ruby in our quest to
master Rails. This morning, I stumbled on a good reason to do so. So, to
the ever growing list of reasons, I add this:
I have a hash of user-input values that I want to do some tests on and
then save the original content once the tests pass. My original code
looked like
value = a_hash[key]
value.gsub!(''-'', '''')
value.gsub!(''$'', '''')
etc
Imagine my surprise when I later wrote the contents of a_hash[key] to
the database, only to find that it had been changed! Some testing in
script/console illustrates the situation:
>> h = {"1"=>"2008-06-17"}
=> {"1"=>"2008-06-17"}>> v = h["1"]
=> "2008-06-17">> v.gsub!(''-'', '''')
=> "20080617">> v
=> "20080617">> h
=> {"1"=>"20080617"}
Now, a little thought about the fact that Ruby is object oriented, and
therefore variables are probably just pointers, makes this sensible. But
for those who are not accustomed to object oriented programming, or a
language that is *fully* object oriented (that''s my dilemma), this
might
not be so obvious. One of two methods on Object can be used to rectify
the problem:
Object#dup:
>> h = {"1"=>"2008-06-17"}
=> {"1"=>"2008-06-17"}>> v = h["1"].dup
=> "2008-06-17">> v.gsub!(''-'', '''')
=> "20080617">> h
=> {"1"=>"2008-06-17"}>> v
=> "20080617"
or
Object#clone:
>> h = {"1"=>"2008-06-17"}
=> {"1"=>"2008-06-17"}>> v = h["1"].clone
=> "2008-06-17">> v.gsub!(''-'', '''')
=> "20080617">> v
=> "20080617">> h
=> {"1"=>"2008-06-17"}
Do read the Ruby docs before using dup or clone, to make sure you
understand what they are doing.
Maybe this post will save someone a little head scratching.
Peace,
Phillip
--
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On 17 Jun 2008, at 16:15, Phillip Koebbe wrote:> > We''ve heard the more knowledgeable of the community say that we should > invest some time into learning and understanding Ruby in our quest to > master Rails. This morning, I stumbled on a good reason to do so. > So, to > the ever growing list of reasons, I add this: > > I have a hash of user-input values that I want to do some tests on and > then save the original content once the tests pass. My original code > looked like > > value = a_hash[key] > value.gsub!(''-'', '''') > value.gsub!(''$'', '''') > etc > > Imagine my surprise when I later wrote the contents of a_hash[key] to > the database, only to find that it had been changed! Some testing in > script/console illustrates the situation:An additional trick is to call freeze on things you don''t want people changing by accident. Fred --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Phillip Koebbe schrieb:> We''ve heard the more knowledgeable of the community say that we should > invest some time into learning and understanding Ruby in our quest to > master Rails. This morning, I stumbled on a good reason to do so. So, to > the ever growing list of reasons, I add this: > > I have a hash of user-input values that I want to do some tests on and > then save the original content once the tests pass. My original code > looked like > > value = a_hash[key] > value.gsub!(''-'', '''') > value.gsub!(''$'', '''') > etc >or just use: value = a_hash[key].gsub(''-'', '''') value.gsub!(''$'', '''') etc. Martin --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
> An additional trick is to call freeze on things you don''t want people > changing by accident. > > FredThanks, Fred. I''ll keep that in mind for future use. It looks like it will work well in some situations, but not so well in others.> or just use: > > value = a_hash[key].gsub(''-'', '''') > value.gsub!(''$'', '''') > etc. > > MartinI thought about something like that, Martin. The reason I didn''t go with something like that is the process can one 0..n steps on a value. The example I used was very simple and just a smidge of what I''m actually doing. In some cases, the first thing I might do is a gsub, in others it might be an attempt to case the value to a Date. So just grabbing it out initially is the most flexible thing to do. But you''re certainly correct in that this would be a way to get around the problem. Peace, Phillip -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---