range<T> static method

FormeValidator<T> range<T>(
  1. double min,
  2. double max, {
  3. String errorText = '',
})

when valid:

  1. value is null
  2. value >= min && value <= max

Implementation

static FormeValidator<T> range<T>(double min, double max,
    {String errorText = ''}) {
  return (f, T v) =>
      (v == null || (v as num >= min && v <= max)) ? null : errorText;
}