Throws an error when the value specified by a given pointer is not valid or can't be made valid for the property identified by a given key.
- iOS 2.0+
- macOS 10.3+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
A pointer to a new value for the property identified by
in. This method may modify or replace the value in order to make it valid.
The name of one of the receiver's properties. The key must specify an attribute or a to-one relationship.
A Boolean set to
true if the value pointed at by
io is valid for the property identified by
in, or if the method is able to modify the value at
io to make it valid; otherwise
The default implementation of this function searches the class of the receiver for a property specific validation function with a particular signature, allowing that function to determine the outcome of the validation. For it to be found, the property specific validation function must be exposed to Objective-C, must be named according to the pattern
validate<In, must take a single, optional
Any pointer argument, and must throw. For example, for a property named
some, the validation function is:
If you define such a function, the default implementation of
validate calls it when asked to validate the corresponding property, allowing your function to either alter the input value or throw an error.
If no such function exists for a particular property,
validatereturns without taking any other action. In other words, by default, the general validation call succeeds if you don't explicitly provide a validation function for the given property.