Package org.zkoss.zul

## Interface CustomConstraint

-     public interface CustomConstraint

  Additional interface implemented with `Constraint` to denote a constraint supports a custom way to display the error message. If this interface is implemented, the default error box won't be displayed. Rather, `showCustomError(org.zkoss.zk.ui.Component, org.zkoss.zk.ui.WrongValueException)` is called.

  Since 5.0.0, `CustomConstraint` has the higher priority than `ClientConstraint`. In other words, `ClientConstraint` is ignored if both defined. On the other hand, the client validation object (`ClientConstraint.getClientConstraint()`) can implement the showCustomError method to do the similar job at the client.

  Author:
    tomyeh
  See Also:
    `Constraint`, `ClientConstraint`

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `void` | `showCustomError​(Component comp, WrongValueException ex)` | To display the error message in a custom way.

- - ### Method Detail

    - #### showCustomError

          void showCustomError​(Component comp,
                               WrongValueException ex)

      To display the error message in a custom way. Note: this method is called either with a error or not, depending on whether ex is null.
      Parameters:
        `comp` - the component causing the error.
        `ex` - the error to display, or null to clear the error message.