# parse method

int parse (String source, { int radix, @deprecated int onError(String source) })
override

Parse `source` as a, possibly signed, integer literal and return its value.

The `source` must be a non-empty sequence of base-`radix` digits, optionally prefixed with a minus or plus sign ('-' or '+'). It must not be `null`.

The `radix` must be in the range 2..36. The digits used are first the decimal digits 0..9, and then the letters 'a'..'z' with values 10 through 35. Also accepts upper-case letters with the same values as the lower-case ones.

If no `radix` is given then it defaults to 10. In this case, the `source` digits may also start with `0x`, in which case the number is interpreted as a hexadecimal integer literal, When `int` is implemented by 64-bit signed integers, hexadecimal integer literals may represent values larger than 263, in which case the value is parsed as if it is an unsigned number, and the resulting value is the corresponding signed integer value.

For any int `n` and valid radix `r`, it is guaranteed that `n == int.parse(n.toRadixString(r), radix: r)`.

If the `source` string does not contain a valid integer literal, optionally prefixed by a sign, a FormatException is thrown (unless the deprecated `onError` parameter is used, see below).

Instead of throwing and immediately catching the FormatException, instead use tryParse to handle a parsing error. Example:

    var value = int.tryParse(text);
    if (value == null) ... handle the problem

The `onError` parameter is deprecated and will be removed. Instead of `int.parse(string, onError: (string) => ...)`, you should use `int.tryParse(string) ?? (...)`.

When the source string is not valid and `onError` is provided, whenever a FormatException would be thrown, `onError` is instead called with `source` as argument, and the result of that call is returned by parse.

## Implementation

    external static int parse(String source,
        {int radix, @deprecated int onError(String source)});