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
Related
After a lot of research and brainstorm finally i give up for it and need a help to convert the forwardslash to single backslash But I am not able to do.
Here is some steps which i followed but it does n't works
"C:/projects/test/code".gsub('/','\\') => "C:\\projects\\test\\code"
"C:/projects/test/code".gsub('/','\\\\') => "C:\\projects\\test\\code"
"C:/projects/test/code".gsub('/',"\'\\'") => "C:'projects/test/codeprojects'test/codetest'codecode"
The result which i expect to be should like:
=> "C:\projects\test\code"
Any help and suggestions accepted please help
You did it already with this:
"C:/projects/test/code".gsub('\', '\\') # => "C:\\projects\\test\\code"
Likely you are confused by \\ in output. It's normal. Just try to puts this:
puts "C:/projects/test/code".gsub(/\//, '\\') # => C:\projects\test\code
Updated:
\ is used in Ruby (and not only) for multiline string concatenation so when you just type it in irb, for example, it continues reading user's input.
Some notes about irb:
when you execute some command in irb it outputs the result for debugging purposes:
irb> "foo\r\nbar"
=> "foo\r\nba"
This line contains \r\n what means go to the beginning of the new new line. So if you want to see it in human mode just print it and it gives:
irb> puts "foo\r\nbar"
foo
bar
If you want to prevent output you can use semicolon:
irb> s = "foo\r\nbar";
irb* puts s
foo
bar
What you get in your first example is exactly what you need. In IRB/Pry the representation differs, because REPL is intended to support copy-paste, and the string you see is the exact string with single backward slashes, how one would type it inside double quotes. You might also note double quotes around the string in the REPL representation, which do not belong to the string itself either.
Here is another more explicit way to accomplish a task:
result = "C:/projects/test/code".split('/').join('\\')
#⇒ "C:\\projects\\test\\code"
See:
puts result
#⇒ C:\projects\test\code
result.count("\\")
#⇒ 3
As a matter of fact, Windows does indeed understand the path with forward slashes, so you probably don’t need this conversion at all.
i may recieve these two strings:
base = Base64.encode64(File.open("/home/usr/Desktop/test", "rb").read)
=> "YQo=\n"
string = File.open("/home/usr/Desktop/test", "rb").read
=> "a\n"
what i have tried so far is to check string with regular expression i-e. /([A-Za-z0-9+\/]{4})*([A-Za-z0-9+\/]{4}|[A-Za-z0-9+\/]{3}=|[A-Za-z0-9+\/]{2}==$)/ but this would be very heavy if the file is big.
I also have tried base.encoding.name and string.encoding.name but both returns the same.
I have also seen this post and got regular expression solution but any other solution ?
Any idea ? I just want to get is the string is actually text or base64 encoded text....
You can use something like this, not very performant but you are guaranteed not to get false positives:
require 'base64'
def base64?(value)
value.is_a?(String) && Base64.strict_encode64(Base64.decode64(value)) == value
end
The use of strict_encode64 versus encode64 prevents Ruby from inadvertently inserting newlines if you have a long string. See this post for details.
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...
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.