The create phase of an object type may contain messages that are defined simply by identifying them as a combination of other defined messages. Such messages are referred to as "create combination messages." Typically, such messages have the following form:
- create: aZone setOption: optionValue;For this message to be a valid create combination message, the object type must already have the create: and setOption: messages defined (either locally or by inheritance). The meaning of this message is then identical to the following sequence (where SomeType is the name of a type implementing the combination message):
- anObject = [SomeType createBegin: aZone]; - [anObject setOption: optionValue]; - anObject = [anObject createEnd];Create combination messages are provided as a convenience for commonly used options. Some combination messages also have their own custom implementing methods so that creation is faster when using the combination message. Any such implementation, however, is required to implement the parts of the combination message so that its meaning is identical to the results that would be obtained if the separate parts were requested in separate message.