int.parse and double.parse error question

[Shailen Tuli]

Both int.parse and double.parse come with internal error handling options.

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

external static double parse(String source, [double handleError(String source)]);

Can anyone point me to a practical example for error handling within these methods?

- Shailen Tuli

[Yohan Beschi]

If the string can't be parsed, instead of using a try/catch you can use a function handling the error and returning a default value.

- Shailen Tuli

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[Alex Tatumizer]

This "onError" callback would be much more useful if system could pass the following parameters:

string being parsed 

position where error was detected

value that would be returned if string ended at error position

Then I would at least know some use case. Right now, what's the point? Ignoring user's input and substituting your own? BTW, calling it a "default value" is a joke, right?

 
 

[Shailen Tuli]

The string being passed *is* passed to the onError callback. I'm just not sure what I can do with it. Check to see if it has illegal characters and throw a FormatException with a better error message than the default? Honestly, I can't imagine using this in real code.

Also, I wish the int.parse() and double.parse() used consistent signatures.  The error handler is a named param in int.parse and a positional parameter in double.parse.  

[James Wendel]

Just for reference:  http://api.dartlang.org/docs/releases/latest/dart_core/int.html#parse

Method signature:

int parse(String source, {int radix, int onError(String source)})

Example:

  

print(int.parse("42", onError: (s) => 0));

[James Wendel]

Shailen: I have submitted a bug to this effect (making int.parse and double.parse signatures more similar):

https://code.google.com/p/dart/issues/detail?id=9375

[Ladislav Thon]

Shailen: I have submitted a bug to this effect (making int.parse and double.parse signatures more similar):

https://code.google.com/p/dart/issues/detail?id=9375

This should definitely be fixed. Starred! :-)

LT