pattern_input_formatter library Null safety


An implementation of NumberInputFormatter that converts a numeric input to credit card number form (4-digit grouping). For example, a input of 12345678 should be formatted to 1234 5678.
An implementation of TextInputFormatter provides a way to input date form with TextField, such as dd/MM/yyyy. In order to guide user about input form, the formatter will provide TextField a placeholder --/--/---- as soon as user start editing. During editing session, the formatter will replace appropriate placeholder characters by user's input.
An abstract class extends from TextInputFormatter and does numeric filter. It has an abstract method _format() that lets its children override it to format input displayed on TextField
An implementation of NumberInputFormatter automatically inserts thousands separators to numeric input. For example, a input of 1234 should be formatted to 1,234.


INDEX_NOT_FOUND → const int