I am wondering how do I pass a false value to my ruby script.
If I invoke:
ruby myscript.rb false
and then in my script if I say:
my_class.new(*ARGV)
or my_class.new(ARGV[0])
basically a string with value "false" gets passed. Clearly if I say
if(ARGV[0]){ do something} .. this gets executed even if value passed is false.
Can I change my function signature to auto-covert paramter to boolean ..so that I dont have to do
if(ARGV[0]=='true')
You need to evaluate the command-line argument. Anything passed on the command line is a string, that's all the command line knows about.
For example, you could monkey-patch String (untested):
class String
def to_b
self =~ /^(true|t|yes|y|1)$/i
end
end
Or write a utility, or use the command-line option parser (long-term best bet), or...
^ at the front: /^(true|t|yes|y|1)$/iAlternatively, if you want to do more sophisticated commandline parsing with option switches, including Boolean ones, take a look at Ruby's built-in OptionParser.
def to_b(string)
case string
when /^(true|t|yes|y|1)$/i then true
when /^(false|f|no|n|0)$/i then false
else raise "Cannot convert to boolean: #{string}"
end
end
This is based on Dave Newton's answer with two differences:
More symmetry -- if you are explicit with tests on the 'true' test, I think you should also be symmetrical on the 'false' test.
Just say no to /(monkey|duck) p(at|un)ching)/ key classes like String!
You CANNOT pass objects from command line. Only object you can pass is a String. I guess at some point in your program you have to do:
if(ARGV[0]=='true')
Here’s a little string helper for converting a string to a bool; it adds a .to_bool method to strings. If the string is equal to true or t or yes or y or 1, the result will be true; otherwise false.
class String
def to_bool
!!(self =~ /^(true|t|yes|y|1)$/i)
end
end
Examples:
"aaa".to_bool #=> false
"t".to_bool #=> true
'foo'?