str = "Hello☺ World☹"
Expected output is:
"Hello:) World:("
I can do this: str.gsub("☺", ":)").gsub("☹", ":(")
Is there any other way so that I can do this in a single function call?. Something like:
str.gsub(['s1', 's2'], ['r1', 'r2'])
7 Answers
Since Ruby 1.9.2, String#gsub accepts hash as a second parameter for replacement with matched keys. You can use a regular expression to match the substring that needs to be replaced and pass hash for values to be replaced.
Like this:
'hello'.gsub(/[eo]/, 'e' => 3, 'o' => '*') #=> "h3ll*"
'(0) 123-123.123'.gsub(/[()-,. ]/, '') #=> "0123123123"
In Ruby 1.8.7, you would achieve the same with a block:
dict = { 'e' => 3, 'o' => '*' }
'hello'.gsub /[eo]/ do |match|
dict[match.to_s]
end #=> "h3ll*"
4 Comments
Marnen Laibow-Koser
Cool, didn't know about that. Kind of a nicer version of Perl
tr.
Sprachprofi
Note that this is not the same as calling str.gsub(key, value) on every element of the hash. If something is matched by the regexp but doesn't have an entry in the hash, it will be deleted.
jpbalarini
@NarenSisodiya, actually it should be: '(0) 123-123.123'.gsub(/[()\-,. ]/, '') You need to add the escape character to '-'.
Greg Blass
Yeah that line there is wrong: '(0) 123-123.123'.gsub(/[()-,. ]/, '') You either need to escape the dash or move it to the front.
Set up a mapping table:
map = {'☺' => ':)', '☹' => ':(' }
Then build a regex:
re = Regexp.new(map.keys.map { |x| Regexp.escape(x) }.join('|'))
And finally, gsub:
s = str.gsub(re, map)
If you're stuck in 1.8 land, then:
s = str.gsub(re) { |m| map[m] }
You need the Regexp.escape in there in case anything you want to replace has a special meaning within a regex. Or, thanks to steenslag, you could use:
re = Regexp.union(map.keys)
and the quoting will be take care of for you.
6 Comments
mu is too short
@steenslag: That's a nice modification.
Andrew Grimm
String#gsub accepts strings as the pattern parameter: "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.".
mu is too short
@Andrew: Yeah but we have multiple strings to replace, hence the regex.
content01
what if the keys of the map are regex expressions? the replacement doesn't seem to work
mu is too short
@content01: Off the top of my head, I think you'd have to go one by one in that case:
map.each { |re, v| ... } |
You could do something like this:
replacements = [ ["☺", ":)"], ["☹", ":("] ]
replacements.each {|replacement| str.gsub!(replacement[0], replacement[1])}
There may be a more efficient solution, but this at least makes the code a bit cleaner
6 Comments
DanneManne
Isn't it suppose to be
replacements.each?
SwiftMango
This is just more complicated and slower.
Nathan Manousos
The return value for
each is the collection it was invoked upon. stackoverflow.com/questions/11596879/…
artm
to have it return the result and not change str:
replacements.reduce(str){|str,replacement| str.gsub(replacement[0],replacement[1])}
Ben Lings
@artm you can also do
replacements.inject(str) { |str, (k,v)| str.gsub(k,v) } and avoid needing to do [0] and [1]. |
Late to the party but if you wanted to replace certain chars with one, you could use a regex
string_to_replace.gsub(/_|,| /, '-')
In this example, gsub is replacing underscores(_), commas (,) or ( ) with a dash (-)
1 Comment
Automatico
this would be even better like this:
string_to_replace.gsub(/[_- ]/, '-')Another simple way, and yet easy to read is the following:
str = '12 ene 2013'
map = {'ene' => 'jan', 'abr'=>'apr', 'dic'=>'dec'}
map.each {|k,v| str.sub!(k,v)}
puts str # '12 jan 2013'
Comments
You can also use tr to replace multiple characters in a string at once,
Eg., replace "h" to "m" and "l" to "t"
"hello".tr("hl", "mt")
=> "metto"
looks simple, neat and faster (not much difference though) than gsub
puts Benchmark.measure {"hello".tr("hl", "mt") }
0.000000 0.000000 0.000000 ( 0.000007)
puts Benchmark.measure{"hello".gsub(/[hl]/, 'h' => 'm', 'l' => 't') }
0.000000 0.000000 0.000000 ( 0.000021)
Comments
Riffing on naren's answer above, I'd go with
tr = {'a' => '1', 'b' => '2', 'z' => '26'}
mystring.gsub(/[#{tr.keys}]/, tr)
So
'zebraazzeebra'.gsub(/[#{tr.keys}]/, tr) returns
"26e2r112626ee2r1"
String#trto do the trick, but the replacements being multiple charcters means I can't use that.