SecTransformSetAttributeAction(_:_:_:_:)

Declaration

func SecTransformSetAttributeAction(_ ref: SecTransformImplementationRef, _ action: CFString, _ attribute: SecTransformStringOrAttribute?, _ newAction: @escaping  SecTransformAttributeActionBlock) -> CFError?

Parameters

• ref:

  A Sectransformimplementationref that is bound to an instance of a custom transform.

• action:

  The behavior to be set.

  Use Ksectransformactionattributenotification to add a block that is called when an attribute is set. If the name is NULL, then the supplied block is called for all set attributes except for ones that have a specific block as a handler.

  Use Ksectransformactionattributevalidation to add a block that is called to validate the input to an attribute.

• attribute:

  The name of the attribute that will be handled. An attribute reference may also be given here. A NULL value indicates that the supplied action is for all attributes.

• newAction:

  A Sectransformattributeactionblock which implements the behavior.

Return Value

An error on failure, or NULL on success. In Objective-C, call the CFRelease function to free the error’s memory when you are done with it.

Discussion

The kSecTransformActionProcessData action used with the SecTransformSetDataAction(_:_:_:) function is a special case of a SecTransformSetAttributeAction(_:_:_:_:) action. If this is called on the input attribute then it will overwrite any kSecTransformActionProcessData action.

You may call this function multiple times for either a named attribute or for all attributes when the attribute parameter is NULL. The last call takes precedence.