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validateValue(_:forKey:)

Validates a property value for a given key.

Declaration

func validateValue(_ value: AutoreleasingUnsafeMutablePointer<AnyObject?>, forKey key: String) throws

Parameters

  • value:

    A pointer to an object.

  • key:

    The name of one of the receiver’s properties.

Discussion

This method is responsible for two things: coercing the value into an appropriate type for the object, and validating it according to the object’s rules.

The default implementation provided by NSManagedObject consults the object’s entity description to coerce the value and to check for basic errors, such as a null value when that isn’t allowed and the length of strings when a field width is specified for the attribute. It then searches for a method of the form validate<Key>:error: and invokes it if it exists.

You can implement methods of the form validate<Key>:error: to perform validation that is not possible using the constraints available in the property description. If it finds an unacceptable value, your validation method should return false and in error an NSError object that describes the problem. For more details, see Managed Object Validation. For inter-property validation (to check for combinations of values that are invalid), see validateForUpdate() and related methods.

See Also

Managing Data Validation