Stripping the first character of a string

Question

i have

string = "$575.00 "
string.to_f
// => 0.0

string = "575.00 "
string.to_f
// => 575.0

the value coming in is in this format and i need to insert into a database field that is decimal any suggestions

"$575.00 " 

Answer 1

you can use regex for that:

s/^.//

As laways, this is PCRE syntax.

In Ruby, you can use the sub() method of the string class to replace the string:

result = string.sub(/^./,"")

This should work.

[EDIT]

Ok, someone asked what's the gsub() is for:

gsub() acts like sub() but with the /g modifier in PCRE (for global replacement):

s/a/b/

in PCRE is

string.sub(/a/, "b")

and

s/a/b/g

is

string.gsub(/a/, "b")

in Ruby

Answer 2

You could try something like this.

string = string[1..-1] if string.match(/^\$/)

Or this.

string.gsub!(/^\$/, '')

Remember to put that backslash in your Regexp, it also means "end of string."

Answer 3

We did this so often we wrote an extension to String called cost_to_f:

class String
  def cost_to_f
    self.delete('$,').to_f
  end
end

We store such extensions in config/initializers/extensions/string.rb.

You can then simply call:

"$5,425.55".cost_to_f   #=> 5425.55

If you are using this method rarely, the best bet is to simply create a function, since adding functions to core classes is not exactly something I would recommend lightly:

def cost_to_f(string)
  string.delete('$,').to_f
end

If you need it in more than one class, you can always put it in a module, then include that module wherever you need it.

---

One more tidbit. You mentioned that you need to process this string when it is being written to the database. With ActiveRecord, the best way to do this is:

class Item < ActiveRecord::Base
  def price=(p)
    p = p.cost_to_f if p.is_a?(String)  
    write_attribute(:price, p)
  end
end

---

EDIT: Updated to use String#delete!

Answer 4

What I'd use (instead of regular expressions) is simply the built-in slice! method in the String class. For example,

s = "Some string"
s.slice!(0) # Deletes and returns the 0th character from the string. 
s # => "ome string"

Documentation here.

Answer 5

So many answers... i'll try to summarize all that are available now, before give own answer.

1. string.gsub(/[\$,]/, '')
   string.gsub!(/^\$/, '')
2. string[1..-1]
3. string.slice(0) # => "ome string"
4. s/^.//

1. Why (g)sub and regexp Just for deleting a character? String#tr is faster and shorter. String#delete is even better.
2. Good, fast, simple. Power of reverse indexing.
3. Hm... looks like it returns "S". Because it is an alias to String#[]
4. Perl? /me is cheking question tags...

And my advice is: What if you have not dollar, but yena? Or what if you don't even have anything before numbers? So i'll prefer:

string[/\d.+/]

This will crop leading non-decimal symbols, that prevent to_f to work well.

P.S.: By the way. It's known, that float is bad practice for storing money amounts. http://stackoverflow.com/questions/61872/use-float-or-decimal-for-accounting-application-dollar-amount