I am just wondering if there is any method to remove string from another string? Something like this:
class String
def remove(s)
self[s.length, self.length - s.length]
end
end
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9 Answers
You can use the slice method:
a = "foobar"
a.slice! "foo"
=> "foo"
a
=> "bar"
there is a non '!' version as well. More info can be seen in the documentation about other versions as well: http://www.ruby-doc.org/core/classes/String.html#method-i-slice-21
11 Comments
Matheus Moreira
Very elegant! You can also use
[]s for the non-bang version.
Mike
This has a bad side effect of returning the deleted text (or text searched for). Unfortunate for chaining on the result of the deletion.
jhabbott
How do you return the sliced string and not affect the original? For example if I have "hello world", I want to slice "hello " and return just the "world" part, without modifying the original string object?
Ernest
@Mike
"foobar".tap{|s| s.slice!("foo")}.upcase
rusty
@bcackerman --
delete wouldn't work, since it deletes all the characters you pass in: 'hello world'.delete('hello') #=> ' wrd' |
How about str.gsub("subString", "")
Check out the Ruby Doc
4 Comments
Alex D
sub would be more appropriate than gsub, since the OP only wants to remove the substring from the beginning of the string, not all through the string (look at his sample code). And using a regex, like this, would be better: str.sub(/^subString/, '') -- because it ensures that the substring will definitely be removed only from the beginning.
David Moles
@AlexD Using a regex would be better, but it's dangerous if we can't be sure
subString doesn't include any regex special characters.Alex D
@DavidMoles, in this case,
/^subString/ is a literal, so we can be very sure it doesn't include any metacharacters. If you are substituting some other string into a regex, you can do this: /#{Regexp.escape(str)}/.David Moles
In the answer, yes, but not in the OP's question. Thanks for the pointer to
Regexp.escape(), though.If it is a the end of the string, you can also use chomp:
"hello".chomp("llo") #=> "he"
answered May 19, 2015 at 10:07
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3 Comments
Fernando Gonzalez Sanchez
if the expression was a.chomp("llo"), chomp! is more precise.
Ardee Aram
This is cleaner than slice!, as this has no side effects.
amoebe
If it is from the beginning of the string, you can also use
chomp in combination with reverse: "hello".reverse.chomp("he".reverse).reverse #=> "llo"Ruby 2.5+
If your substring is at the beginning of in the end of a string, then Ruby 2.5 has introduced the methods for this:
- delete_prefix for removing a substring from the beginning of the string
- delete_suffix for removing a substring from the end of the string
Comments
If you only have one occurrence of the target string you can use:
str[target] = ''
or
str.sub(target, '')
If you have multiple occurrences of target use:
str.gsub(target, '')
For instance:
asdf = 'foo bar'
asdf['bar'] = ''
asdf #=> "foo "
asdf = 'foo bar'
asdf.sub('bar', '') #=> "foo "
asdf = asdf + asdf #=> "foo barfoo bar"
asdf.gsub('bar', '') #=> "foo foo "
If you need to do in-place substitutions use the "!" versions of gsub! and sub!.
2 Comments
Peter Butkovic
ruby is fun! really enjoy seeing stuff like:
asdf['bar'] = ''
Jmoney38
I wouldn't call that "fun" - non-intuitive, perhaps.
If you are using Rails there's also remove.
E.g. "Testmessage".remove("message") yields "Test".
Warning: this method removes all occurrences
3 Comments
Dylan Pierce
This isn't a vanilla Ruby answer, but the accepted answer isn't quite what most people are looking for. Unfortunately the
slice method doesn't return the portion of the string that's sliced, it returns the "knife"
Bennett Talpers
@DylanPierce it's pretty easy to implement a function that does that using
slice! def gimme_the_slice(my_string, my_slice) my_string.slice!(my_slice) my_string Dylan Pierce
Ah that's right, bang-ifying is how Ruby modifies the existing variable. Thanks @BennettTalpers
If you are using rails or at less activesupport you got String#remove and String#remove! method
def remove!(*patterns)
patterns.each do |pattern|
gsub! pattern, ""
end
self
end
source: http://api.rubyonrails.org/classes/String.html#method-i-remove
Comments
If I'm interpreting right, this question seems to ask for something like a minus (-) operation between strings, i.e. the opposite of the built-in plus (+) operation (concatenation).
Unlike the previous answers, I'm trying to define such an operation that must obey the property:
IF c = a + b THEN c - a = b AND c - b = a
We need only three built-in Ruby methods to achieve this:
'abracadabra'.partition('abra').values_at(0,2).join == 'cadabra'.
I won't explain how it works because it can be easily understood running one method at a time.
Here is a proof of concept code:
# minus_string.rb
class String
def -(str)
partition(str).values_at(0,2).join
end
end
# Add the following code and issue 'ruby minus_string.rb' in the console to test
require 'minitest/autorun'
class MinusString_Test < MiniTest::Test
A,B,C='abra','cadabra','abracadabra'
def test_C_eq_A_plus_B
assert C == A + B
end
def test_C_minus_A_eq_B
assert C - A == B
end
def test_C_minus_B_eq_A
assert C - B == A
end
end
One last word of advice if you're using a recent Ruby version (>= 2.0): use Refinements instead of monkey-patching String like in the previous example.
It is as easy as:
module MinusString
refine String do
def -(str)
partition(str).values_at(0,2).join
end
end
end
and add using MinusString before the blocks where you need it.
1 Comment
wondersz1
+1 for the concepts of refinements. While monkey-patching String class is probably an overkill for this use case, sometimes we do have to monkey-patch things and concept of refinements really shines at it.
here's what I'd do
2.2.1 :015 > class String; def remove!(start_index, end_index) (end_index - start_index + 1).times{ self.slice! start_index }; self end; end;
2.2.1 :016 > "idliketodeleteHEREallthewaytoHEREplease".remove! 14, 32
=> "idliketodeleteplease"
2.2.1 :017 > ":)".remove! 1,1
=> ":"
2.2.1 :018 > "ohnoe!".remove! 2,4
=> "oh!"
Formatted on multiple lines:
class String
def remove!(start_index, end_index)
(end_index - start_index + 1).times{ self.slice! start_index }
self
end
end
Comments
