A Char::Reader allows iterating a String by Chars.
As soon as you instantiate a Char::Reader it will decode the first char in the String, which can be accessed by invoking #current_char. At this point #pos, the current position in the string, will equal zero. Successive calls to #next_char return the next chars in the string, advancing #pos.
Note that the null character '\0' will be returned in #current_char when the end is reached (as well as when the string is empty). Thus, #has_next? will return false only when #pos is equal to the string's bytesize, in which case #current_char will always be '\0'.
Creates a reader with the specified string positioned at byte index pos.
Creates a reader that will be positioned at the last char of the given string.
Returns the current character.
Returns the size of the #current_char (in bytes) as if it were encoded in UTF-8.
If there was an error decoding the current char because of an invalid UTF-8 byte sequence, returns the byte that produced the invalid encoding.
Returns true if there is a character left to read.
Returns true if there are characters before the current one.
Reads the next character in the string, #pos is incremented.
Returns the position of the current character.
Sets #pos to pos.
Returns the previous character, #pos is decremented.
Returns the reader's String.
Enumerable(Char)
Struct
Value
Object
Object
Creates a reader with the specified string positioned at byte index pos.
Creates a reader that will be positioned at the last char of the given string.
Returns the current character.
reader = Char::Reader.new("ab")
reader.current_char # => 'a'
reader.next_char
reader.current_char # => 'b' Returns the size of the #current_char (in bytes) as if it were encoded in UTF-8.
reader = Char::Reader.new("aé")
reader.current_char_width # => 1
reader.next_char
reader.current_char_width # => 2 If there was an error decoding the current char because of an invalid UTF-8 byte sequence, returns the byte that produced the invalid encoding. Returns 0 if the char would've been out of bounds. Otherwise returns nil.
Returns true if there is a character left to read. The terminating byte '\0' is considered a valid character by this method.
reader = Char::Reader.new("a")
reader.has_next? # => true
reader.peek_next_char # => '\0' Returns true if there are characters before the current one.
Reads the next character in the string, #pos is incremented. Raises IndexError if the reader is at the end of the #string.
reader = Char::Reader.new("ab")
reader.next_char # => 'b' Returns the next character in the #string without incrementing #pos. Raises IndexError if the reader is at the end of the #string.
reader = Char::Reader.new("ab")
reader.peek_next_char # => 'b'
reader.current_char # => 'a' Returns the position of the current character.
reader = Char::Reader.new("ab")
reader.pos # => 0
reader.next_char
reader.pos # => 1 Sets #pos to pos.
reader = Char::Reader.new("abc")
reader.next_char
reader.next_char
reader.pos = 0
reader.current_char # => 'a' Returns the previous character, #pos is decremented. Raises IndexError if the reader is at the beginning of the #string
© 2012–2020 Manas Technology Solutions.
Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/0.35.1/Char/Reader.html