How to check whether a string contains a substring in Ruby

Question

I have a string variable with content   varMessage                   hi thsid sdfhsjdf dfjsd sdjfsdn n                  my name is balaji so n               call  myFunction int const amp   n               void  secondFunction char const amp   n                                                            this is last line liobrary so    In the string I have to find a sub-string    hi thsid sdfhsjdf dfjsd sdjfsdn n     my name is balaji so n   call  myFunction int const amp   n    How can I find it  I need to determine whether the sub-string is present or not

User · Answer

You can use the String Element Reference method which is []

Inside the [] can either be a literal substring, an index, or a regex:

> s='abcdefg'
=> "abcdefg"
> s['a']
=> "a"
> s['z']
=> nil

Since nil is functionally the same as false and any substring returned from [] is true you can use the logic as if you use the method .include?:

0> if s[sub_s]
1>    puts "\"#{s}\" has \"#{sub_s}\""
1> else 
1*    puts "\"#{s}\" does not have \"#{sub_s}\""
1> end
"abcdefg" has "abc"

0> if s[sub_s]
1>    puts "\"#{s}\" has \"#{sub_s}\""
1> else 
1*    puts "\"#{s}\" does not have \"#{sub_s}\""
1> end
"abcdefg" does not have "xyz"

Just make sure you don't confuse an index with a sub string:

> '123456790'[8]    # integer is eighth element, or '0'
=> "0"              # would test as 'true' in Ruby
> '123456790'['8']  
=> nil              # correct

You can also use a regex:

> s[/A/i]
=> "a"
> s[/A/]
=> nil

User · Answer

Expanding on Clint Pachl s answer   Regex matching in Ruby returns nil when the expression doesn t match  When it does  it returns the index of the character where the match happens  For example    foobar      bar     returns 3  foobar      foo     returns 0  foobar      zzz     returns nil   It s important to note that in Ruby only nil and the boolean expression false evaluate to false  Everything else  including an empty Array  empty Hash  or the Integer 0  evaluates to true   That s why the  foo  example above works  and why   if  string      regex    works as expected  only entering the  true  part of the if block if a match occurred

User · Answer

If case is irrelevant  then a case-insensitive regular expression is a good solution    aBcDe      bcd i    evaluates as true   This will also work for multi-line strings   See Ruby s Regexp class for more information

User · Answer

A more succinct idiom than the accepted answer above that s available in Rails  from 3 1 0 and above  is  in    my string    abcdefg  if  cde  in  my string   puts   cde  is in the String     puts  i e  String includes  cde   end   I also think it s more readable   See the in  documentation for more information    Note again that it s only available in Rails  and not pure Ruby

User · Answer

How to check whether a string contains a substring in Ruby    When you say  check   I assume you want a boolean returned in which case you may use String match   match  accepts strings or regexes as its first parameter  if it s the former then it s automatically converted to a regex  So your use case would be   str    string  str match   strings     gt  false str match   string      gt  true str match   strin       gt  true str match   trin        gt  true str match   tri         gt  true   String match  has the added benefit of an optional second argument which specifies an index from which to search the string  By default this is set to 0   str match   tri  0      gt  true str match   tri  1      gt  true str match   tri  2      gt  false

User · Answer

You can also do this     my string    Hello world   if my string  Hello     puts  It has  Hello   else   puts  No  Hello  found  end      gt   It has  Hello     This example uses Ruby s String     method

User · Answer

Ternary way  my string include   ahr      puts  String includes ahr      puts  String does not include ahr     OR  puts  my string include   ahr      String includes ahr     String not includes ahr

User · Answer

You can use the include  method   my string    abcdefg  if my string include   cde     puts  String includes  cde   end

User · Answer

user input   gets chomp user input downcase   if user input include   substring       Do something end   This will help you check if the string contains substring or not  puts  Enter a string  user input   gets chomp    Ex  Tommy user input downcase        tommy   if user input include   s       puts  Found  else     puts  Not found  end

[ruby] How to check whether a string contains a substring in Ruby

Examples related to ruby

Examples related to string