String
inflections define new methods on the String
class to transform names for different purposes. For instance, you can figure out the name of a table from the name of a class.
'ScaleScore'.tableize # => "scale_scores"
- A
- B
- C
- D
- E
- F
- H
- I
- L
- M
- P
- R
- S
- T
- U
BLANK_RE | = | /\A[[:space:]]*\z/ |
ENCODED_BLANKS | = | Concurrent::Map.new do |h, enc| h[enc] = Regexp.new(BLANK_RE.source.encode(enc), BLANK_RE.options | Regexp::FIXEDENCODING) end |
Enables more predictable duck-typing on String-like classes. See Object#acts_like?
.
If you pass a single integer, returns a substring of one character at that position. The first character of the string is at position 0, the next at position 1, and so on. If a range is supplied, a substring containing characters at offsets given by the range is returned. In both cases, if an offset is negative, it is counted from the end of the string. Returns nil
if the initial offset falls outside the string. Returns an empty string if the beginning of the range is greater than the end of the string.
str = "hello"
str.at(0) # => "h"
str.at(1..3) # => "ell"
str.at(-2) # => "l"
str.at(-2..-1) # => "lo"
str.at(5) # => nil
str.at(5..-1) # => ""
If a Regexp is given, the matching portion of the string is returned. If a String
is given, that given string is returned if it occurs in the string. In both cases, nil
is returned if there is no match.
str = "hello"
str.at(/lo/) # => "lo"
str.at(/ol/) # => nil
str.at("lo") # => "lo"
str.at("ol") # => nil
A string is blank if it's empty or contains whitespaces only:
''.blank? # => true
' '.blank? # => true
"\t\n\r".blank? # => true
' blah '.blank? # => false
Unicode whitespace is supported:
"\u00a0".blank? # => true
@return [true, false]
# File activesupport/lib/active_support/core_ext/object/blank.rb, line 122 def blank? # The regexp that matches blank strings is expensive. For the case of empty # strings we can speed up this method (~3.5x) with an empty? call. The # penalty for the rest of strings is marginal. empty? || begin BLANK_RE.match?(self) rescue Encoding::CompatibilityError ENCODED_BLANKS[self.encoding].match?(self) end end
By default, camelize
converts strings to UpperCamelCase. If the argument to camelize is set to :lower
then camelize produces lowerCamelCase.
camelize
will also convert '/' to '::' which is useful for converting paths to namespaces.
'active_record'.camelize # => "ActiveRecord"
'active_record'.camelize(:lower) # => "activeRecord"
'active_record/errors'.camelize # => "ActiveRecord::Errors"
'active_record/errors'.camelize(:lower) # => "activeRecord::Errors"
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 91 def camelize(first_letter = :upper) case first_letter when :upper ActiveSupport::Inflector.camelize(self, true) when :lower ActiveSupport::Inflector.camelize(self, false) else raise ArgumentError, "Invalid option, use either :upper or :lower." end end
Creates a class name from a plural table name like Rails does for table names to models. Note that this returns a string and not a class. (To convert to an actual class follow classify
with constantize
.)
'ham_and_eggs'.classify # => "HamAndEgg"
'posts'.classify # => "Post"
constantize
tries to find a declared constant with the name specified in the string. It raises a NameError
when the name is not in CamelCase or is not initialized. See ActiveSupport::Inflector.constantize
'Module'.constantize # => Module
'Class'.constantize # => Class
'blargle'.constantize # => NameError: wrong constant name blargle
Replaces underscores with dashes in the string.
'puni_puni'.dasherize # => "puni-puni"
Removes the rightmost segment from the constant expression in the string.
'Net::HTTP'.deconstantize # => "Net"
'::Net::HTTP'.deconstantize # => "::Net"
'String'.deconstantize # => ""
'::String'.deconstantize # => ""
''.deconstantize # => ""
See also demodulize
.
Removes the module part from the constant expression in the string.
'ActiveSupport::Inflector::Inflections'.demodulize # => "Inflections"
'Inflections'.demodulize # => "Inflections"
'::Inflections'.demodulize # => "Inflections"
''.demodulize # => ''
See also deconstantize
.
The inverse of String#include?
. Returns true if the string does not include the other string.
"hello".exclude? "lo" # => false
"hello".exclude? "ol" # => true
"hello".exclude? ?h # => false
Returns the first character. If a limit is supplied, returns a substring from the beginning of the string until it reaches the limit value. If the given limit is greater than or equal to the string length, returns a copy of self.
str = "hello"
str.first # => "h"
str.first(1) # => "h"
str.first(2) # => "he"
str.first(0) # => ""
str.first(6) # => "hello"
Creates a foreign key name from a class name. separate_class_name_and_id_with_underscore
sets whether the method should put '_' between the name and 'id'.
'Message'.foreign_key # => "message_id"
'Message'.foreign_key(false) # => "messageid"
'Admin::Post'.foreign_key # => "post_id"
Returns a substring from the given position to the end of the string. If the position is negative, it is counted from the end of the string.
str = "hello"
str.from(0) # => "hello"
str.from(3) # => "lo"
str.from(-2) # => "lo"
You can mix it with to
method and do fun things like:
str = "hello"
str.from(0).to(-1) # => "hello"
str.from(1).to(-2) # => "ell"
Marks a string as trusted safe. It will be inserted into HTML with no additional escaping performed. It is your responsibility to ensure that the string contains no malicious content. This method is equivalent to the raw
helper in views. It is recommended that you use sanitize
instead of this method. It should never be called on user input.
Capitalizes the first word, turns underscores into spaces, and (by default)strips a trailing '_id' if present. Like titleize
, this is meant for creating pretty output.
The capitalization of the first word can be turned off by setting the optional parameter capitalize
to false. By default, this parameter is true.
The trailing '_id' can be kept and capitalized by setting the optional parameter keep_id_suffix
to true. By default, this parameter is false.
'employee_salary'.humanize # => "Employee salary"
'author_id'.humanize # => "Author"
'author_id'.humanize(capitalize: false) # => "author"
'_id'.humanize # => "Id"
'author_id'.humanize(keep_id_suffix: true) # => "Author Id"
Converts String
to a TimeWithZone in the current zone if Time.zone
or Time.zone_default
is set, otherwise converts String
to a Time
via String#to_time
Indents the lines in the receiver:
<<EOS.indent(2)
def some_method
some_code
end
EOS
# =>
def some_method
some_code
end
The second argument, indent_string
, specifies which indent string to use. The default is nil
, which tells the method to make a guess by peeking at the first indented line, and fallback to a space if there is none.
" foo".indent(2) # => " foo"
"foo\n\t\tbar".indent(2) # => "\t\tfoo\n\t\t\t\tbar"
"foo".indent(2, "\t") # => "\t\tfoo"
While indent_string
is typically one space or tab, it may be any string.
The third argument, indent_empty_lines
, is a flag that says whether empty lines should be indented. Default is false.
"foo\n\nbar".indent(2) # => " foo\n\n bar"
"foo\n\nbar".indent(2, nil, true) # => " foo\n \n bar"
Same as indent
, except it indents the receiver in-place.
Returns the indented string, or nil
if there was nothing to indent.
# File activesupport/lib/active_support/core_ext/string/indent.rb, line 7 def indent!(amount, indent_string = nil, indent_empty_lines = false) indent_string = indent_string || self[/^[ \t]/] || " " re = indent_empty_lines ? /^/ : /^(?!$)/ gsub!(re, indent_string * amount) end
Wraps the current string in the ActiveSupport::StringInquirer
class, which gives you a prettier way to test for equality.
env = 'production'.inquiry
env.production? # => true
env.development? # => false
Returns true
if string has utf_8 encoding.
utf_8_str = "some string".encode "UTF-8"
iso_str = "some string".encode "ISO-8859-1"
utf_8_str.is_utf8? # => true
iso_str.is_utf8? # => false
Returns the last character of the string. If a limit is supplied, returns a substring from the end of the string until it reaches the limit value (counting backwards). If the given limit is greater than or equal to the string length, returns a copy of self.
str = "hello"
str.last # => "o"
str.last(1) # => "o"
str.last(2) # => "lo"
str.last(0) # => ""
str.last(6) # => "hello"
Multibyte proxy
mb_chars
is a multibyte safe proxy for string methods.
It creates and returns an instance of the ActiveSupport::Multibyte::Chars
class which encapsulates the original string. A Unicode safe version of all the String
methods are defined on this proxy class. If the proxy class doesn't respond to a certain method, it's forwarded to the encapsulated string.
>> "lj".upcase
=> "lj"
>> "lj".mb_chars.upcase.to_s
=> "LJ"
NOTE: An above example is useful for pre Ruby 2.4. Ruby 2.4 supports Unicode case mappings.
Method
chaining
All the methods on the Chars proxy which normally return a string will return a Chars object. This allows method chaining on the result of any of these methods.
name.mb_chars.reverse.length # => 12
Interoperability and configuration
The Chars object tries to be as interchangeable with String
objects as possible: sorting and comparing between String
and Char work like expected. The bang! methods change the internal string representation in the Chars object. Interoperability problems can be resolved easily with a to_s
call.
For more information about the methods defined on the Chars proxy see ActiveSupport::Multibyte::Chars
. For information about how to change the default Multibyte behavior see ActiveSupport::Multibyte
.
Replaces special characters in a string so that it may be used as part of a 'pretty' URL.
class Person
def to_param
"#{id}-#{name.parameterize}"
end
end
@person = Person.find(1)
# => #<Person id: 1, name: "Donald E. Knuth">
<%= link_to(@person.name, person_path) %>
# => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
To preserve the case of the characters in a string, use the preserve_case
argument.
class Person
def to_param
"#{id}-#{name.parameterize(preserve_case: true)}"
end
end
@person = Person.find(1)
# => #<Person id: 1, name: "Donald E. Knuth">
<%= link_to(@person.name, person_path) %>
# => <a href="/person/1-Donald-E-Knuth">Donald E. Knuth</a>
Returns the plural form of the word in the string.
If the optional parameter count
is specified, the singular form will be returned if count == 1
. For any other value of count
the plural will be returned.
If the optional parameter locale
is specified, the word will be pluralized as a word of that language. By default, this parameter is set to :en
. You must define your own inflection rules for languages other than English.
'post'.pluralize # => "posts"
'octopus'.pluralize # => "octopi"
'sheep'.pluralize # => "sheep"
'words'.pluralize # => "words"
'the blue mailman'.pluralize # => "the blue mailmen"
'CamelOctopus'.pluralize # => "CamelOctopi"
'apple'.pluralize(1) # => "apple"
'apple'.pluralize(2) # => "apples"
'ley'.pluralize(:es) # => "leyes"
'ley'.pluralize(1, :es) # => "ley"
Returns a new string with all occurrences of the patterns removed.
str = "foo bar test"
str.remove(" test") # => "foo bar"
str.remove(" test", /bar/) # => "foo "
str # => "foo bar test"
Alters the string by removing all occurrences of the patterns.
str = "foo bar test"
str.remove!(" test", /bar/) # => "foo "
str # => "foo "
safe_constantize
tries to find a declared constant with the name specified in the string. It returns nil
when the name is not in CamelCase or is not initialized. See ActiveSupport::Inflector.safe_constantize
'Module'.safe_constantize # => Module
'Class'.safe_constantize # => Class
'blargle'.safe_constantize # => nil
The reverse of pluralize
, returns the singular form of a word in a string.
If the optional parameter locale
is specified, the word will be singularized as a word of that language. By default, this parameter is set to :en
. You must define your own inflection rules for languages other than English.
'posts'.singularize # => "post"
'octopi'.singularize # => "octopus"
'sheep'.singularize # => "sheep"
'word'.singularize # => "word"
'the blue mailmen'.singularize # => "the blue mailman"
'CamelOctopi'.singularize # => "CamelOctopus"
'leyes'.singularize(:es) # => "ley"
Returns the string, first removing all whitespace on both ends of the string, and then changing remaining consecutive whitespace groups into one space each.
Note that it handles both ASCII and Unicode whitespace.
%{ Multi-line
string }.squish # => "Multi-line string"
" foo bar \n \t boo".squish # => "foo bar boo"
Performs a destructive squish. See String#squish
.
str = " foo bar \n \t boo"
str.squish! # => "foo bar boo"
str # => "foo bar boo"
Strips indentation in heredocs.
For example in
if options[:usage]
puts <<-USAGE.strip_heredoc
This command does such and such.
Supported options are:
-h This message
...
USAGE
end
the user would see the usage message aligned against the left margin.
Technically, it looks for the least indented non-empty line in the whole string, and removes that amount of leading whitespace.
Creates the name of a table like Rails does for models to table names. This method uses the pluralize
method on the last word in the string.
'RawScaledScorer'.tableize # => "raw_scaled_scorers"
'ham_and_egg'.tableize # => "ham_and_eggs"
'fancyCategory'.tableize # => "fancy_categories"
Capitalizes all the words and replaces some characters in the string to create a nicer looking title. titleize
is meant for creating pretty output. It is not used in the Rails internals.
The trailing '_id','Id'.. can be kept and capitalized by setting the optional parameter keep_id_suffix
to true. By default, this parameter is false.
titleize
is also aliased as titlecase
.
'man from the boondocks'.titleize # => "Man From The Boondocks"
'x-men: the last stand'.titleize # => "X Men: The Last Stand"
'string_ending_with_id'.titleize(keep_id_suffix: true) # => "String Ending With Id"
Returns a substring from the beginning of the string to the given position. If the position is negative, it is counted from the end of the string.
str = "hello"
str.to(0) # => "h"
str.to(3) # => "hell"
str.to(-2) # => "hell"
You can mix it with from
method and do fun things like:
str = "hello"
str.from(0).to(-1) # => "hello"
str.from(1).to(-2) # => "ell"
Converts a string to a Date
value.
"1-1-2012".to_date # => Sun, 01 Jan 2012
"01/01/2012".to_date # => Sun, 01 Jan 2012
"2012-12-13".to_date # => Thu, 13 Dec 2012
"12/13/2012".to_date # => ArgumentError: invalid date
Converts a string to a DateTime
value.
"1-1-2012".to_datetime # => Sun, 01 Jan 2012 00:00:00 +0000
"01/01/2012 23:59:59".to_datetime # => Sun, 01 Jan 2012 23:59:59 +0000
"2012-12-13 12:50".to_datetime # => Thu, 13 Dec 2012 12:50:00 +0000
"12/13/2012".to_datetime # => ArgumentError: invalid date
Converts a string to a Time
value. The form
can be either :utc or :local (default :local).
The time is parsed using Time.parse method. If form
is :local, then the time is in the system timezone. If the date part is missing then the current date is used and if the time part is missing then it is assumed to be 00:00:00.
"13-12-2012".to_time # => 2012-12-13 00:00:00 +0100
"06:12".to_time # => 2012-12-13 06:12:00 +0100
"2012-12-13 06:12".to_time # => 2012-12-13 06:12:00 +0100
"2012-12-13T06:12".to_time # => 2012-12-13 06:12:00 +0100
"2012-12-13T06:12".to_time(:utc) # => 2012-12-13 06:12:00 UTC
"12/13/2012".to_time # => ArgumentError: argument out of range
# File activesupport/lib/active_support/core_ext/string/conversions.rb, line 21 def to_time(form = :local) parts = Date._parse(self, false) used_keys = %i(year mon mday hour min sec sec_fraction offset) return if (parts.keys & used_keys).empty? now = Time.now time = Time.new( parts.fetch(:year, now.year), parts.fetch(:mon, now.month), parts.fetch(:mday, now.day), parts.fetch(:hour, 0), parts.fetch(:min, 0), parts.fetch(:sec, 0) + parts.fetch(:sec_fraction, 0), parts.fetch(:offset, form == :utc ? 0 : nil) ) form == :utc ? time.utc : time.to_time end
Truncates a given text
after a given length
if text
is longer than length
:
'Once upon a time in a world far far away'.truncate(27)
# => "Once upon a time in a wo..."
Pass a string or regexp :separator
to truncate text
at a natural break:
'Once upon a time in a world far far away'.truncate(27, separator: ' ')
# => "Once upon a time in a..."
'Once upon a time in a world far far away'.truncate(27, separator: /\s/)
# => "Once upon a time in a..."
The last characters will be replaced with the :omission
string (defaults to “…”) for a total length not exceeding length
:
'And they found that many people were sleeping better.'.truncate(25, omission: '... (continued)')
# => "And they f... (continued)"
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 66 def truncate(truncate_at, options = {}) return dup unless length > truncate_at omission = options[:omission] || "..." length_with_room_for_omission = truncate_at - omission.length stop = \ if options[:separator] rindex(options[:separator], length_with_room_for_omission) || length_with_room_for_omission else length_with_room_for_omission end "#{self[0, stop]}#{omission}" end
Truncates a given text
after a given number of words (words_count
):
'Once upon a time in a world far far away'.truncate_words(4)
# => "Once upon a time..."
Pass a string or regexp :separator
to specify a different separator of words:
'Once<br>upon<br>a<br>time<br>in<br>a<br>world'.truncate_words(5, separator: '<br>')
# => "Once<br>upon<br>a<br>time<br>in..."
The last characters will be replaced with the :omission
string (defaults to “…”):
'And they found that many people were sleeping better.'.truncate_words(5, omission: '... (continued)')
# => "And they found that many... (continued)"
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 95 def truncate_words(words_count, options = {}) sep = options[:separator] || /\s+/ sep = Regexp.escape(sep.to_s) unless Regexp === sep if self =~ /\A((?>.+?#{sep}){#{words_count - 1}}.+?)#{sep}.*/m $1 + (options[:omission] || "...") else dup end end
The reverse of camelize
. Makes an underscored, lowercase form from the expression in the string.
underscore
will also change '::' to '/' to convert namespaces to paths.
'ActiveModel'.underscore # => "active_model"
'ActiveModel::Errors'.underscore # => "active_model/errors"
Converts just the first character to uppercase.
'what a Lovely Day'.upcase_first # => "What a Lovely Day"
'w'.upcase_first # => "W"
''.upcase_first # => ""