A String object holds and manipulates an arbitrary sequence of bytes, typically representing characters. String objects may be created using String::new or as literals.
Because of aliasing issues, users of strings should be aware of the methods that modify the contents of a String object. Typically, methods with names ending in “!” modify their receiver, while those without a “!” return a new String. However, there are exceptions, such as String#[]=.
Element Reference — If passed a single index, returns a substring of one character at that index. If passed a start index and a length, returns a substring containing length characters starting at the start index. If passed a range, its beginning and end are interpreted as offsets delimiting the substring to be returned.
In these three cases, if an index is negative, it is counted from the end of the string. For the start and range cases the starting index is just before a character and an index matching the string’s size. Additionally, an empty string is returned when the starting index for a character range is at the end of the string.
Returns nil if the initial index falls outside the string or the length is negative.
If a Regexp is supplied, the matching portion of the string is returned. If a capture follows the regular expression, which may be a capture group index or name, follows the regular expression that component of the MatchData is returned instead.
If a match_str is given, that string is returned if it occurs in the string.
Returns nil if the regular expression does not match or the match string cannot be found.
a = "hello there" a[1] #=> "e" a[2, 3] #=> "llo" a[2..3] #=> "ll" a[-3, 2] #=> "er" a[7..-2] #=> "her" a[-4..-2] #=> "her" a[-2..-4] #=> "" a[11, 0] #=> "" a[11] #=> nil a[12, 0] #=> nil a[12..-1] #=> nil a[/[aeiou](.)\1/] #=> "ell" a[/[aeiou](.)\1/, 0] #=> "ell" a[/[aeiou](.)\1/, 1] #=> "l" a[/[aeiou](.)\1/, 2] #=> nil a[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, "non_vowel"] #=> "l" a[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, "vowel"] #=> "e" a["lo"] #=> "lo" a["bye"] #=> nil
Returns a new array populated with the given objects.
Array.[]( 1, 'a', /^A/) # => [1, "a", /^A/] Array[ 1, 'a', /^A/ ] # => [1, "a", /^A/] [ 1, 'a', /^A/ ] # => [1, "a", /^A/]
Element Reference — Returns the element at index, or returns a subarray starting at the start index and continuing for length elements, or returns a subarray specified by range of indices.
Negative indices count backward from the end of the array (-1 is the last element). For start and range cases the starting index is just before an element. Additionally, an empty array is returned when the starting index for an element range is at the end of the array.
Returns nil if the index (or starting index) are out of range.
a = [ "a", "b", "c", "d", "e" ] a[2] + a[0] + a[1] #=> "cab" a[6] #=> nil a[1, 2] #=> [ "b", "c" ] a[1..3] #=> [ "b", "c", "d" ] a[4..7] #=> [ "e" ] a[6..10] #=> nil a[-3, 3] #=> [ "c", "d", "e" ] # special cases a[5] #=> nil a[6, 1] #=> nil a[5, 1] #=> [] a[5..10] #=> []
Bit Reference—Returns the nth bit in the binary representation of int, where int[0] is the least significant bit.
a = 0b11001100101010 30.downto(0) {|n| print a[n] } #=> 0000000000000000011001100101010 a = 9**15 50.downto(0) {|n| print a[n] } #=> 000101110110100000111000011110010100111100010111001
In principle, n[i] is equivalent to (n >> i) & 1. Thus, any negative index always returns zero:
p 255[-1] #=> 0
Range operations n[i, len] and n[i..j] are naturally extended.
n[i, len] equals to (n >> i) & ((1 << len) - 1).
n[i..j] equals to (n >> i) & ((1 << (j - i + 1)) - 1).
n[i...j] equals to (n >> i) & ((1 << (j - i)) - 1).
n[i..] equals to (n >> i).
n[..j] is zero if n & ((1 << (j + 1)) - 1) is zero. Otherwise, raises an ArgumentError.
n[...j] is zero if n & ((1 << j) - 1) is zero. Otherwise, raises an ArgumentError.
Note that range operation may exhaust memory. For example, -1[0, 1000000000000] will raise NoMemoryError.
Invokes the continuation. The program continues from the end of the callcc block. If no arguments are given, the original callcc returns nil. If one argument is given, callcc returns it. Otherwise, an array containing args is returned.
callcc {|cont| cont.call } #=> nil callcc {|cont| cont.call 1 } #=> 1 callcc {|cont| cont.call 1, 2, 3 } #=> [1, 2, 3]
Equivalent to calling Dir.glob([string,…], 0).
Return a value from the database by locating the key string provided. If the key is not found, returns nil.
Attribute Reference—Returns the value of the given struct member or the member at the given index. Raises NameError if the member does not exist and IndexError if the index is out of range.
Customer = Struct.new(:name, :address, :zip) joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345) joe["name"] #=> "Joe Smith" joe[:name] #=> "Joe Smith" joe[0] #=> "Joe Smith"
Retrieves the value corresponding to key.
Returns the value of an attribute.
require "ostruct" person = OpenStruct.new("name" => "John Smith", "age" => 70) person[:age] # => 70, same as person.age
Creates a new set containing the given objects.
Set[1, 2] # => #<Set: {1, 2}> Set[1, 2, 1] # => #<Set: {1, 2}> Set[1, 'c', :s] # => #<Set: {1, "c", :s}>
Returns sym.to_s[].
Returns the value in the database associated with the given key string.
If no value is found, returns nil.
Returns the n-th subgroup in the most recent match.
s = StringScanner.new("Fri Dec 12 1975 14:39") s.scan(/(\w+) (\w+) (\d+) /) # -> "Fri Dec 12 " s[0] # -> "Fri Dec 12 " s[1] # -> "Fri" s[2] # -> "Dec" s[3] # -> "12" s.post_match # -> "1975 14:39" s.pre_match # -> "" s.reset s.scan(/(?<wday>\w+) (?<month>\w+) (?<day>\d+) /) # -> "Fri Dec 12 " s[0] # -> "Fri Dec 12 " s[1] # -> "Fri" s[2] # -> "Dec" s[3] # -> "12" s[:wday] # -> "Fri" s[:month] # -> "Dec" s[:day] # -> "12" s.post_match # -> "1975 14:39" s.pre_match # -> ""
Returns the value of Collection specified by a1, a2,.…
dict = WIN32OLE.new('Scripting.Dictionary') dict.add('ruby', 'Ruby') puts dict['ruby'] # => 'Ruby' (same as `puts dict.item('ruby')')
Remark: You can not use this method to get the property.
excel = WIN32OLE.new('Excel.Application') # puts excel['Visible'] This is error !!! puts excel.Visible # You should to use this style to get the property.
Creates a new hash populated with the given objects.
Similar to the literal { key => value, ... }. In the first form, keys and values occur in pairs, so there must be an even number of arguments.
The second and third form take a single argument which is either an array of key-value pairs or an object convertible to a hash.
Hash["a", 100, "b", 200] #=> {"a"=>100, "b"=>200} Hash[ [ ["a", 100], ["b", 200] ] ] #=> {"a"=>100, "b"=>200} Hash["a" => 100, "b" => 200] #=> {"a"=>100, "b"=>200}
Element Reference—Retrieves the value object corresponding to the key object. If not found, returns the default value (see Hash::new for details).
h = { "a" => 100, "b" => 200 } h["a"] #=> 100 h["c"] #=> nil
Returns the value for the environment variable name if it exists:
ENV['foo'] = '0' ENV['foo'] # => "0"
Returns nil if the named variable does not exist:
ENV.clear ENV['foo'] # => nil
Raises an exception if name is invalid. See Invalid Names and Values.
Creates a matrix where each argument is a row.
Matrix[ [25, 93], [-1, 66] ]
=> 25 93
-1 66
Returns element (i,j) of the matrix. That is: row i, column j.