# tf.compat.v1.flags.validator

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A function decorator for defining a flag validator.

    tf.compat.v1.flags.validator(
        flag_name,
        message='Flag validation failed',
        flag_values=_flagvalues.FLAGS
    )

Registers the decorated function as a validator for flag_name, e.g.::

    @flags.validator('foo')
    def _CheckFoo(foo):
      ...

See :func:`register_validator` for the specification of checker function.

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| ## Args ||
|---|---|
| `flag_name` | str \| FlagHolder, name or holder of the flag to be checked. Positional-only parameter. |
| `message` | str, error text to be shown to the user if checker returns False. If checker raises flags.ValidationError, message from the raised error will be shown. |
| `flag_values` | flags.FlagValues, optional FlagValues instance to validate against. |

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| ## Returns ||
|---|---|
| A function decorator that registers its function argument as a validator. ||

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| ## Raises ||
|---|---|
| `AttributeError` | Raised when flag_name is not registered as a valid flag name. |

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