1 files changed, 114 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/string/access.rb b/activesupport/lib/active_support/core_ext/string/access.rb
new file mode 100644
index 0000000000..4ca24028b0
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/string/access.rb
@@ -0,0 +1,114 @@
+# frozen_string_literal: true
+
+class String
+  # 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
+  def at(position)
+    self[position]
+  end
+
+  # 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"
+  def from(position)
+    self[position..-1]
+  end
+
+  # 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"
+  def to(position)
+    self[0..position]
+  end
+
+  # 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"
+  def first(limit = 1)
+    ActiveSupport::Deprecation.warn(
+      "Calling String#first with a negative integer limit " \
+      "will raise an ArgumentError in Rails 6.1."
+    ) if limit < 0
+    if limit == 0
+      ""
+    elsif limit >= size
+      dup
+    else
+      to(limit - 1)
+    end
+  end
+
+  # 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"
+  def last(limit = 1)
+    ActiveSupport::Deprecation.warn(
+      "Calling String#last with a negative integer limit " \
+      "will raise an ArgumentError in Rails 6.1."
+    ) if limit < 0
+    if limit == 0
+      ""
+    elsif limit >= size
+      dup
+    else
+      from(-limit)
+    end
+  end
+end