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#[]=.
Returns the substring of self specified by the arguments.
When the single Integer argument index is given, returns the 1-character substring found in self at offset index:
'bar'[2] # => "r"
Counts backward from the end of self if index is negative:
'foo'[-3] # => "f"
Returns nil if index is out of range:
'foo'[3] # => nil 'foo'[-4] # => nil
When the two Integer arguments start and length are given, returns the substring of the given length found in self at offset start:
'foo'[0, 2] # => "fo" 'foo'[0, 0] # => ""
Counts backward from the end of self if start is negative:
'foo'[-2, 2] # => "oo"
Special case: returns a new empty String if start is equal to the length of self:
'foo'[3, 2] # => ""
Returns nil if start is out of range:
'foo'[4, 2] # => nil 'foo'[-4, 2] # => nil
Returns the trailing substring of self if length is large:
'foo'[1, 50] # => "oo"
Returns nil if length is negative:
'foo'[0, -1] # => nil
When the single Range argument range is given, derives start and length values from the given range, and returns values as above:
'foo'[0..1] is equivalent to 'foo'[0, 2].
'foo'[0...1] is equivalent to 'foo'[0, 1].
When the Regexp argument regexp is given, and the capture argument is 0, returns the first matching substring found in self, or nil if none found:
'foo'[/o/] # => "o" 'foo'[/x/] # => nil s = 'hello there' s[/[aeiou](.)\1/] # => "ell" s[/[aeiou](.)\1/, 0] # => "ell"
If argument capture is given and not 0, it should be either an Integer capture group index or a String or Symbol capture group name; the method call returns only the specified capture (see Regexp Capturing):
s = 'hello there' s[/[aeiou](.)\1/, 1] # => "l" s[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, "non_vowel"] # => "l" s[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, :vowel] # => "e"
If an invalid capture group index is given, nil is returned. If an invalid capture group name is given, IndexError is raised.
When the single String argument substring is given, returns the substring from self if found, otherwise nil:
'foo'['oo'] # => "oo" 'foo'['xx'] # => nil
String#slice is an alias for String#[].
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/]
Returns elements from self; does not modify self.
When a single Integer argument index is given, returns the element at offset index:
a = [:foo, 'bar', 2] a[0] # => :foo a[2] # => 2 a # => [:foo, "bar", 2]
If index is negative, counts relative to the end of self:
a = [:foo, 'bar', 2] a[-1] # => 2 a[-2] # => "bar"
If index is out of range, returns nil.
When two Integer arguments start and length are given, returns a new Array of size length containing successive elements beginning at offset start:
a = [:foo, 'bar', 2] a[0, 2] # => [:foo, "bar"] a[1, 2] # => ["bar", 2]
If start + length is greater than self.length, returns all elements from offset start to the end:
a = [:foo, 'bar', 2] a[0, 4] # => [:foo, "bar", 2] a[1, 3] # => ["bar", 2] a[2, 2] # => [2]
If start == self.size and length >= 0, returns a new empty Array.
If length is negative, returns nil.
When a single Range argument range is given, treats range.min as start above and range.size as length above:
a = [:foo, 'bar', 2] a[0..1] # => [:foo, "bar"] a[1..2] # => ["bar", 2]
Special case: If range.start == a.size, returns a new empty Array.
If range.end is negative, calculates the end index from the end:
a = [:foo, 'bar', 2] a[0..-1] # => [:foo, "bar", 2] a[0..-2] # => [:foo, "bar"] a[0..-3] # => [:foo]
If range.start is negative, calculates the start index from the end:
a = [:foo, 'bar', 2] a[-1..2] # => [2] a[-2..2] # => ["bar", 2] a[-3..2] # => [:foo, "bar", 2]
If range.start is larger than the array size, returns nil.
a = [:foo, 'bar', 2] a[4..1] # => nil a[4..0] # => nil a[4..-1] # => nil
When a single Enumerator::ArithmeticSequence argument aseq is given, returns an Array of elements corresponding to the indexes produced by the sequence.
a = ['--', 'data1', '--', 'data2', '--', 'data3'] a[(1..).step(2)] # => ["data1", "data2", "data3"]
Unlike slicing with range, if the start or the end of the arithmetic sequence is larger than array size, throws RangeError.
a = ['--', 'data1', '--', 'data2', '--', 'data3'] a[(1..11).step(2)] # RangeError (((1..11).step(2)) out of range) a[(7..).step(2)] # RangeError (((7..).step(2)) out of range)
If given a single argument, and its type is not one of the listed, tries to convert it to Integer, and raises if it is impossible:
a = [:foo, 'bar', 2] # Raises TypeError (no implicit conversion of Symbol into Integer): a[:foo]
Array#slice is an alias for Array#[].
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]
Dir[ string [, string ...] [, base: path] [, sort: true] ] -> array
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, or ‘nil` if there is no such 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 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.
Returns a new Hash object populated with the given objects, if any. See Hash::new.
With no argument, returns a new empty Hash.
When the single given argument is a Hash, returns a new Hash populated with the entries from the given Hash.
h = {foo: 0, bar: 1, baz: 2} Hash[h] # => {:foo=>0, :bar=>1, :baz=>2}
When the single given argument is an Array of 2-element Arrays, returns a new Hash object wherein each 2-element array forms a key-value entry:
Hash[ [ [:foo, 0], [:bar, 1] ] ] # => {:foo=>0, :bar=>1}
When the argument count is an even number; returns a new Hash object wherein each successive pair of arguments has become a key-value entry:
Hash[:foo, 0, :bar, 1] # => {:foo=>0, :bar=>1}
Raises an exception if the argument list does not conform to any of the above.
Returns the value associated with the given key, if found:
h = {foo: 0, bar: 1, baz: 2} h[:foo] # => 0
If key is not found, returns a default value (see Default Values):
h = {foo: 0, bar: 1, baz: 2} h[:nosuch] # => 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.
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.
Returns element or elements of the vector.
Match Reference – MatchData acts as an array, and may be accessed using the normal array indexing techniques. mtch[0] is equivalent to the special variable $&, and returns the entire matched string. mtch[1], mtch[2], and so on return the values of the matched backreferences (portions of the pattern between parentheses).
m = /(.)(.)(\d+)(\d)/.match("THX1138.") m #=> #<MatchData "HX1138" 1:"H" 2:"X" 3:"113" 4:"8"> m[0] #=> "HX1138" m[1, 2] #=> ["H", "X"] m[1..3] #=> ["H", "X", "113"] m[-3, 2] #=> ["X", "113"] m = /(?<foo>a+)b/.match("ccaaab") m #=> #<MatchData "aaab" foo:"aaa"> m["foo"] #=> "aaa" m[:foo] #=> "aaa"