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
"$575.00 "
We did this so often we wrote an extension to String called cost_to_f:
class String
def cost_to_f
self.delete('$,').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!
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/^.//
Why (g)sub and regexp Just for deleting a character? String#tr is faster and shorter. String#delete is even better.
Good, fast, simple. Power of reverse indexing.
Hm... looks like it returns "S". Because it is an alias to String#[]
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.
Use Float or Decimal for Accounting Application Dollar Amount?
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."
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
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.
Related
The string:
SecureRandom.urlsafe_base64(64)
#=> "nItIZhCvbne9zjU4JUWJOL46y53ERfmuQQW_FN4_ymk2EdbQr1NYOXTJVIeUWXhvRCe4OU3Is2ZEaHpiXXGYxw"
Random::Formatted.urlsafe_base64 implementation:
def urlsafe_base64(n=nil, padding=false)
s = [random_bytes(n)].pack("m0")
s.tr!("+/", "-_")
s.delete!("=") unless padding
s
end
So the question is basically what title says: is there a sane way to check whether string is generated with above method?
Maybe with some regexp? From docs:
The result may contain A-Z, a-z, 0-9, “-” and “_”. “=” is also used if
padding is true.
I would think there is not, because string is just a string, but I need to know if I can rely on anything more than its length while checking it.
Initial problem is that Rollbar gem filters API request Header with ***, and I'd like to change that so that I can see first n characterss of api token to track who made the failing request.
I'm gonna answer the literal question:
is there a sane way to check whether string is generated with above method?
Yes, there is. Kind of. Depends on where your boundaries of "sane" are. :)
Adapted from http://www.schneems.com/2016/01/25/ruby-debugging-magic-cheat-sheet.html
require 'objspace'
require 'securerandom'
ObjectSpace.trace_object_allocations_start
Kernel.send(:define_method, :sup) do |obj|
puts "#{ ObjectSpace.allocation_sourcefile(obj) }:#{ ObjectSpace.allocation_sourceline(obj) }"
end
str = SecureRandom.urlsafe_base64(64)
sup str
# >> /Users/sergio/.rubies/ruby-2.3.3/lib/ruby/2.3.0/securerandom.rb:169
One of the parameters my API controller receives has a big key name and I need to convert it from string to integer, if it is present, before sending it to the model to be persisted. Usually I would do one of the following:
params[:really_big_key_name] = params[:really_big_key_name].to_i unless params[:really_big_key_name].blank?
or
params[:really_big_key_name] = params[:really_big_key_name].present? ? params[:really_big_key_name].to_i : nil
As you can see, the code line becomes big, with more than 80 characters, and I want to stick with Ruby best practices. Is there a shorter, more Ruby way to do the same? Maybe "in place" methods. Something like arrays do with bang methods. Unfortunately, to_i! does not exist for strings, which is exactly what I need.
You could do this:
params[:really_big_key_name] = params[:really_big_key_name].try(:to_i)
I am having trouble formatting my string correctly. I am reading strings from a file and trying to use them as js code.
file_line = blah'blah"blah
string = line.gsub(/'/, "\\\'").gsub(/"/, "\\\"").dump
I want the output to be:
blah\'blah\"blah
But I cant seem to format it right. I have tried a bunch of things.
I'd use a single gsub matching both, ' and ", along with a block to prepend a \:
line = %q{blah'blah"blah}
string = line.gsub(/["']/) { |m| "\\#{m}" }
#=> "blah\\'blah\\\"blah"
puts string
Output:
blah\'blah\"blah
string = "blah'blah\"blah"
puts string.gsub(/'/,"\\\\'").gsub(/"/,'\"') # => blah\'blah\"blah
There's a whole lot of escaping going on here. To be honest I don't really understand the first one, but the second one is simple. I think in the first one we are escaping the backslash we want to add, and then escaping those two backslashes to avoid ruby interpretting them as a reference to the string. Or something. Trying to do a single level of escaping yields this:
puts string.gsub(/'/,"\\'").gsub(/"/,'\"') # => blahblah\"blahblah\"blah
in ruby i can build a Variable with the date like this
irb(main):004:0> a = "#{Date.today}" => "2012-03-23"
But how can i do this with a already created string:
irb(main):005:0> a = '#{Date.today}' => "\#{Date.today}"
The background is, that i'am storing a path with different variables in a database and i need to replace these variables at runtime.
Thanks for any help.
You could eval the string like
a = 'Date.today'
result = eval(a)
While this works, it's can be extremely dangerous if you don't fully control the contents of that string (which is really hard if deal with any kind of user input).
So in general you are advised to never use eval. Instead you could build some simple DSL (domain specific language) where you have tokens in your string that are later replaced with pre-calculated values. A simple example could be:
a = "Today is :today"
result = a.gsub(/:(\w+)/) do |match|
case $1
when "today"
Date.today.to_s
end
end
As you are not evaluing arbitrary Ruby code, this is much safer. Alternatively, depending on your actual usage, you might also be satisfied with String formatting.
If you really want to run arbitrary Ruby code, you can use eval like this:
a = '#{Date.today}'
eval("\"#{a}\"")
I'm developing a web application using rails.
For aesthetic purposes, i need to replace %20 with -
Before: http://localhost:3000/movies/2006/Apna%20Sapna%20Money%20Money
After: http://localhost:3000/movies/2006/Apna-Sapna-Money-Money
Is there anyway i can achieve this in rails?
You should use URI.parse to break it into pieces and then change only the path component:
require 'uri'
u = URI.parse(url)
u.path = u.path.gsub('%20', '-')
url = u.to_s
Just a simple gsub on the whole URL would probably work fine but a little extra paranoia might save you some confusion and suffering down the road. Also, if you're just replacing a literal string rather than a regular expression, you can use a String as the first argument to gsub and avoid some escaping issues:
The pattern is typically a Regexp; if given as a String, any regular expression metacharacters it contains will be interpreted literally, e.g. '\\d' will match a backlash followed by d, instead of a digit.
If your string is stored in the variable url you can use
url.gsub(/%20/, "-")
to return the string you want, or
url.gsub!(/%20/, "-")
to actually modify the value of url with the value you want.
https://github.com/FriendlyId/friendly_id
this is the best way to go about seo urls
You probably want to be saving "Apna-Sapna-Money-Money" within your Movies model as an attribute (I usually call these slugs). Then, to generate these, you might just need to replace spaces in the movie title with hyphens. Something like:
class Movie
before_create :generate_slug
private
def generate_slug
slug = title.gsub(" ", "-")
end
end
Then in your controller action you can simply do a Movie.find_by_slug!(params[:id]) call.
Basically, there should be no reason for users to ever arrive at a URL with %20 in it...