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 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 Synchronous messages: We say that control, or the ability to compute, is gained by holding a token that is passed with a message. The object with the token is executing, or... You can consider there is an activation stack: when object A sends a message to object B, object B goes on to the top of the stack and it can compute. If B responds to A then B is popped from the stack and A, being at the top, begins to compute Messaging

Sept Ron McFadyen Collaboration Diagram Objects are represented similarly to classes in a class model … relationships are indicated clearly Objects may be named or unnamed 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

Sept Ron McFadyen Figure 15.3 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 Figure 15.7 Messages Many messages may be sent across one link Messages numbered 1, 2, 3 are sent in response to receipt of message msg1; message 3.1 is sent in response to message 3

Sept Ron McFadyen Figure 15.8 Message to ‘this’ 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 Figure 15.9 Instance creation We will use a create message to indicate that an object is being instantiated

Sept Ron McFadyen Figure 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.”

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

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

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

Sept Ron McFadyen Figure Iteration

Sept Ron McFadyen Figure 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

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

Sept Ron McFadyen Collaboration Diagram - example Suppose we have classes for POrder, Customer, LineItem, Product with the following class model POrder LineItemProduct Customer * 1 We want to exhibit how objects of these classes communicate in order for the POrder to learn its value

Sept Ron McFadyen Collaboration Diagram - example Suppose POrder does not know its value. To determine its value it must ask each of its line items “what are you worth?”, and then ask the customer “what discount do you get”. Each line doesn’t remember the corresponding products price and so it must interrogate the product to determine the price POrder LineItemProduct Customer * 1

Sept Ron McFadyen Collaboration Diagram :POrder line1:LineItemTYZMonitor:Product line2:LineItemOptMouseX :Product JonesSupply:Customer 1:cost:=reportTotal() 1.1:price:=reportPrice() 2:reportTotal() 2.1:price:=reportPrice() 3:discount:=reportDiscount() reportTotal() Given that the objects below are involved, we show them along with the basic associations Since these are objects, not classes, there are no multiplicities Some message starts things off