User input masking library ported to Xamarin.IOS

Original version: https://github.com/RedMadRobot/input-mask-ios

The library allows to format user input on the fly according to the provided mask and to extract valueable characters.

Masks consist of blocks of symbols, which may include:

• [] — a block for valueable symbols written by user.

Square brackets block may contain any number of special symbols:

1. 0 — mandatory digit. For instance, [000] mask will allow user to enter three numbers: 123.
2. 9 — optional digit . For instance, [00099] mask will allow user to enter from three to five numbers.
3. А — mandatory letter. [AAA] mask will allow user to enter three letters: abc.
4. а — optional letter. [АААааа] mask will allow to enter from three to six letters.
5. _ — mandatory symbol (digit or letter).
6. - — optional symbol (digit or letter).

Other symbols inside square brackets will cause a mask initialization error.

Blocks may contain mixed types of symbols; such that, [000AA] will end up being divided in two groups: [000][AA] (this happens automatically).

Blocks must not contain nested brackets. [[00]000] format will cause a mask initialization error.

Symbols outside the square brackets will take a place in the output. For instance, +7 ([000]) [000]-[0000] mask will format the input field to the form of +7 (123) 456-7890.

• {} — a block for valueable yet fixed symbols, which could not be altered by the user.

Symbols within the square and curly brackets form an extracted value (valueable characters). In other words, [00]-[00] and [00]{-}[00] will format the input to the same form of 12-34, but in the first case the value, extracted by the library, will be equal to 1234, and in the second case it will result in 12-34.

Mask format examples:

1. [00000000000]
2. {401}-[000]-[00]-[00]
3. [000999999]
4. {818}-[000]-[00]-[00]
5. [A][-----------------------------------------------------]
6. [A][_______________________________________________________________]
7. 8 [0000000000]
8. 8([000])[000]-[00]-[00]
9. [0000]{-}[00]
10. +1 ([000]) [000] [00] [00]

The library is distributed under the MIT LICENSE.