StringScanner provides for lexical scanning operations on a String.
require "string_scanner"
s = StringScanner.new("This is an example string")
s.eos? # => false
s.scan(/\w+/) # => "This"
s.scan(/\w+/) # => nil
s.scan(/\s+/) # => " "
s.scan(/\s+/) # => nil
s.scan(/\w+/) # => "is"
s.eos? # => false
s.scan(/\s+/) # => " "
s.scan(/\w+/) # => "an"
s.scan(/\s+/) # => " "
s.scan(/\w+/) # => "example"
s.scan(/\s+/) # => " "
s.scan(/\w+/) # => "string"
s.eos? # => true
s.scan(/\s+/) # => nil
s.scan(/\w+/) # => nil Scanning a string means remembering the position of a scan offset, which is just an index. Scanning moves the offset forward, and matches are sought after the offset; usually immediately after it.
Methods that advance the scan offset:
Methods that look ahead:
Methods that deal with the position of the offset:
Methods that deal with the last match:
Miscellaneous methods:
Returns the n-th subgroup in the most recent match.
Returns the nilable n-th subgroup in the most recent match.
Returns the value that #scan would return, without advancing the scan offset.
Returns the value that #scan_until would return, without advancing the scan offset.
Returns true if the scan offset is at the end of the string.
Writes a representation of the scanner.
Returns the current position of the scan offset.
Sets the position of the scan offset.
Extracts a string corresponding to string[offset,len], without advancing the scan offset.
Resets the scan offset to the beginning and clears the last match.
Returns the remainder of the string after the scan offset.
Tries to match with pattern at the current position.
Scans the string until the pattern is matched.
Attempts to skip over the given pattern beginning with the scan offset.
Attempts to skip until the given pattern is found after the scan offset.
Returns the string being scanned.
Moves the scan offset to the end of the string and clears the last match.
Reference
Reference
Object
Object
Returns the n-th subgroup in the most recent match.
Raises an exception if there was no last match or if there is no subgroup.
require "string_scanner"
s = StringScanner.new("Fri Dec 12 1975 14:39")
regex = /(?<wday>\w+) (?<month>\w+) (?<day>\d+)/
s.scan(regex) # => "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" Returns the nilable n-th subgroup in the most recent match.
Returns nil if there was no last match or if there is no subgroup.
require "string_scanner"
s = StringScanner.new("Fri Dec 12 1975 14:39")
regex = /(?<wday>\w+) (?<month>\w+) (?<day>\d+)/
s.scan(regex) # => "Fri Dec 12"
s[0]? # => "Fri Dec 12"
s[1]? # => "Fri"
s[2]? # => "Dec"
s[3]? # => "12"
s[4]? # => nil
s["wday"]? # => "Fri"
s["month"]? # => "Dec"
s["day"]? # => "12"
s["year"]? # => nil
s.scan(/more/) # => nil
s[0]? # => nil Returns the value that #scan would return, without advancing the scan offset. The last match is still saved, however.
require "string_scanner"
s = StringScanner.new("this is a string")
s.offset = 5
s.check(/\w+/) # => "is"
s.check(/\w+/) # => "is" Returns the value that #scan_until would return, without advancing the scan offset. The last match is still saved, however.
require "string_scanner"
s = StringScanner.new("test string")
s.check_until(/tr/) # => "test str"
s.check_until(/g/) # => "test string" Returns true if the scan offset is at the end of the string.
require "string_scanner"
s = StringScanner.new("this is a string")
s.eos? # => false
s.scan(/(\w+\s?){4}/) # => "this is a string"
s.eos? # => true Writes a representation of the scanner.
Includes the current position of the offset, the total size of the string, and five characters near the current position.
Returns the current position of the scan offset.
Extracts a string corresponding to string[offset,len], without advancing the scan offset.
Resets the scan offset to the beginning and clears the last match.
Returns the remainder of the string after the scan offset.
require "string_scanner"
s = StringScanner.new("this is a string")
s.scan(/(\w+\s?){2}/) # => "this is "
s.rest # => "a string" Tries to match with pattern at the current position. If there's a match, the scanner advances the scan offset, the last match is saved, and it returns the matched string. Otherwise, the scanner returns nil.
require "string_scanner"
s = StringScanner.new("test string")
s.scan(/\w+/) # => "test"
s.scan(/\w+/) # => nil
s.scan(/\s\w+/) # => " string"
s.scan(/.*/) # => "" Scans the string until the pattern is matched. Returns the substring up to and including the end of the match, the last match is saved, and advances the scan offset. Returns nil if no match.
require "string_scanner"
s = StringScanner.new("test string")
s.scan_until(/tr/) # => "test str"
s.scan_until(/tr/) # => nil
s.scan_until(/g/) # => "ing" Attempts to skip over the given pattern beginning with the scan offset. In other words, the pattern is not anchored to the current scan offset.
If there's a match, the scanner advances the scan offset, the last match is saved, and it returns the size of the skipped match. Otherwise it returns nil and does not advance the offset.
This method is the same as #scan, but without returning the matched string.
Attempts to skip until the given pattern is found after the scan offset. In other words, the pattern is not anchored to the current scan offset.
If there's a match, the scanner advances the scan offset, the last match is saved, and it returns the size of the skip. Otherwise it returns nil and does not advance the offset.
This method is the same as #scan_until, but without returning the matched string.
Moves the scan offset to the end of the string and clears the last match.
© 2012–2020 Manas Technology Solutions.
Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/0.35.1/StringScanner.html