In perl, one is able to sort of 'declare' variables by mentioning them
in 'my' statements. Then, if you say 'use strict;', no variables that
weren't previously thus 'declared' are allowed. This is useful in that
it catches typos that might be difficult to detect in testing.
Does ruby have an equivalent mechanism?
Well one can say, that concerning local variables the "my" is
implicit. Instance variables spring into life without "declaration".
In Ruby 1.9 this gives you a warning though.
HTH
R.
On Wed, Jun 9, 2010 at 8:45 AM, lalawawa <usenet@ccjj.info> wrote:
In perl, one is able to sort of 'declare' variables by mentioning them
in 'my' statements. Then, if you say 'use strict;', no variables that
weren't previously thus 'declared' are allowed. This is useful in that
it catches typos that might be difficult to detect in testing.Does ruby have an equivalent mechanism?
--
The best way to predict the future is to invent it.
-- Alan Kay
Better: you do not need an additional declaration, rather Ruby will
catch situations for you where you forgot to initialize (aka assign) a
local variable:
$ ruby19 -e 'puts foo'
-e:1:in `<main>': undefined local variable or method `foo' for
main:Object (NameError)
The grain of salt is this
- this does not work for instance variables, these spring into
existence whenever you use them,
- because there is the method local variable ambiguity you might still
run into erroneous situations when forgetting to initialize a local
variable which shares name with a method.
Kind regards
robert
2010/6/9 lalawawa <usenet@ccjj.info>:
In perl, one is able to sort of 'declare' variables by mentioning them
in 'my' statements. Then, if you say 'use strict;', no variables that
weren't previously thus 'declared' are allowed. This is useful in that
it catches typos that might be difficult to detect in testing.Does ruby have an equivalent mechanism?
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
You can also get an ide / editor that supports auto completion. There is a
link to a giant google spreadsheet running around here somewhere. You might
try looking into that if you are concerned.
On Wed, Jun 9, 2010 at 1:45 AM, lalawawa <usenet@ccjj.info> wrote:
In perl, one is able to sort of 'declare' variables by mentioning them
in 'my' statements. Then, if you say 'use strict;', no variables that
weren't previously thus 'declared' are allowed. This is useful in that
it catches typos that might be difficult to detect in testing.Does ruby have an equivalent mechanism?
Hi Robert,
I assume that if I use the value of an unassigned variable ruby will
catch me. What I am worried about is if I misspell a variable name
while assigning to it.
myLongName = 'woof'
if haveACat
myLoongName += ' and meow'
end
puts myLongName
I misspelled 'myLongName' the second time, so it's like the assinment
didn't happen. If I had been in perl and said 'my myLongName' and 'use
strict', it would have caught the first time I ran it, even if I didn't
test the case where 'haveACat' is true.
Robert Klemme wrote:
2010/6/9 lalawawa <usenet@ccjj.info>:
In perl, one is able to sort of 'declare' variables by mentioning them
in 'my' statements. Then, if you say 'use strict;', no variables that
weren't previously thus 'declared' are allowed. This is useful in that
it catches typos that might be difficult to detect in testing.Does ruby have an equivalent mechanism?
Better: you do not need an additional declaration, rather Ruby will
catch situations for you where you forgot to initialize (aka assign) a
local variable:$ ruby19 -e 'puts foo'
-e:1:in `<main>': undefined local variable or method `foo' for
main:Object (NameError)The grain of salt is this
- this does not work for instance variables, these spring into
existence whenever you use them,- because there is the method local variable ambiguity you might still
run into erroneous situations when forgetting to initialize a local
variable which shares name with a method.Kind regards
robert
Please do not top post.
I assume that if I use the value of an unassigned variable ruby will
catch me. What I am worried about is if I misspell a variable name
while assigning to it.myLongName = 'woof'
if haveACat
myLoongName += ' and meow'
end
puts myLongNameI misspelled 'myLongName' the second time, so it's like the assinment
didn't happen. If I had been in perl and said 'my myLongName' and 'use
strict', it would have caught the first time I ran it, even if I didn't
test the case where 'haveACat' is true.
You can easily test this out for yourself:
$ ruby19 <<XXX
haveACat=true
myLongName = 'woof'
if haveACat
myLoongName += ' and meow'
end
puts myLongName
XXX
-:4:in `<main>': undefined method `+' for nil:NilClass (NoMethodError)
nil does not have many methods so it's likely that the error will surface that way.
Also, writing unit tests or rspecs will catch behavioral errors. I cannot recall many spelling errors that I made in Ruby programs and I can't remember a single one that went unnoticed. So while I agree that Perl seems to provide more safety here for me the practical benefit is small.
This goes a bit in a similar direction as the discussion about dynamically typed scripting languages being unsafe or not suited for large scale applications because they lack type safety of statically typed languages. In theory that all sounds good but it turns out that in practice there are not many issues that would have been caught by static type checking. Other classes of bugs seem more prevalent - in my experience.
Cheers
robert
On 10.06.2010 00:33, lalawawa wrote:
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/