Sept Ron McFadyen Interaction Diagrams - Chapter 15 Describe/illustrate sequence of message exchanges among objects that are working together to achieve some functionality required in the system used to illustrate the design required to achieve the purpose Types Communication/Collaboration diagram Sequence diagram

Sept Ron McFadyen Sample Collaboration Diagram Suppose an event such as a light turning red occurs, and the traffic light must send a message to the camera letting it know that a red light occurred. PortageMain: trafficLight pm: camera changeToRed() 1:changeToRed() 1.1:takePhoto()

Sept Ron McFadyen Sample Sequence Diagram Suppose an event such as a light turning red occurs, and the traffic light must send a message to the camera letting it know that a red light occurred. PortageMain: trafficLightpm: camera changeToRed() takePhoto()

Sept Ron McFadyen Interaction Diagrams Messages asynchronous or synchronous components numbered (collaboration diagram) guard name parameter list name is mandatory... others as required

Sept Ron McFadyen Messaging Synchronous messages asynchronous messages return messages We will assume (at first) that all messages are synchronous: if object A sends a message to object B then A is suspended object B gains control, and B begins to compute object A waits until B responds (i.e. B sends a message back to A) When an asynchronous message is sent from A to B, A does not pause and wait for B to finish … results in multiple threads of control.

Sept Ron McFadyen Collaboration Diagram Timing is understood by the numbering scheme. We use a nested decimal numbering to indicate the order in which messages are sent Many messages may be sent across one link :Student:Student Objects are represented similarly to classes in a class model … relationships are indicated as links between objects named or unnamed :Student:Student 2 nd edition 3 rd edition

Sept Ron McFadyen Collaboration diagram for makePayment Messages numbered 1.1, 1.2, … are sent in response to receipt of message numbered 1. Return messages are often left out

Sept Ron McFadyen Message to ‘this’ or an object itself A message sent from an object to itself (i.e. invoking one of its own methods) is indicated by a reflexive link, but this does not imply a reflexive association

Sept Ron McFadyen Instance creation We will use a create message to indicate that an object is being instantiated

Sept Ron McFadyen Sequence Numbering The initial message triggering the collaboration is unnumbered. All messages sent as the result of an object receiving a message numbered X, are prefixed with “X.” Note: pay special attention to the numbering

Sept Ron McFadyen Complex numbering We need a numbering scheme to know the order of messages

Sept Ron McFadyen Conditional Message A guard (enclosed in square braces [ ] ) indicates a condition that must be true for the message to be sent

Sept Ron McFadyen Mutually exclusive messages a, b, etc are used as suffixes to indicate mutually exclusive messages. A guard would also be used

Sept Ron McFadyen Iteration Numbered 1 Iteration indicator * Guard [i:=1..N]

Sept Ron McFadyen Iteration over a multiobject A multi-object represents a collection of objects. E.g. the SalesLineItems for a Sale; E.g. the ProductSpecifications for a ProductCatalog 2 nd edition

Sept Ron McFadyen Iteration over a collection On the right hand side is one object/instance from the collection E.g. the SalesLineItems for a Sale; E.g. the ProductSpecifications for a ProductCatalog 3 rd edition :Sale lineItems[i]: SalesLineItem t = getTotal 1 * [i=1..n]: st = getSubtotal

Sept Ron McFadyen Messages to a class itself, not an object A message may be sent to the class, and not to a specific object. 2 nd edition

Sept Ron McFadyen Messages to a class itself, not an object A message may be sent to the class, and not to a specific object. 3 rd edition discusses messages sent to a > … in Java, classes are considered instances of class Class… Class is considered a metaclass :Foo > Calendar doX getAvailableLocales 3rd edition