COS3711 Assignment 4 (COMPLETE ANSWERS) 2026 - DUE September 2026

COS3711 Assignment 4 (COMPLETE ANSWERS) 2026 - DUE September 2026; 100% TRUSTED Complete, trusted solutions and explanations. For assistance, Whats-App 0.8.1..2.7.8..3.3.7.2... Question 1 [25 marks] 1.1 Considering the scenario given above, draw a partial UML class diagram that captures the scenario. You should include the necessary classes, class attributes, and class relationships that are mentioned in the scenario. Class constructors and member access specifiers are not required. However, you should ensure that you include all the data members and member functions that show how data will be moved around the application. You should include the Client/GUI class. [You may use a software tool to create the UML class diagram. Use underlining to represent italics in hand-drawn UML class diagrams.] (20) 1.2 It has been argued that the design pattern that would be used here is a behavioural pattern. Do you agree, indicating which pattern would be used and why it is or is not a behavioural pattern? (2) 1.3 It was decided to provide the class that holds the rain data with some reflective functionality. That is, a getData() function should return a single data string that contains all the data held by the class via the class’s meta-object, in a property named data. This function is used only by the meta-object and should not be available to users of the class. module code/101/0/2026 7 Write the class definition for this class showing how this would be set up. You are not required to include functionality or data members not mentioned above, or to code the implementation of the getData() function. (3) Question 2 [30 marks] Consider now the generation of the XML text that will be passed to the graphing applications. The format for the XML text to be generated is the following. rainRecord rain date="2023/01/01" stationAagA100/station mm10/mm /rain rain date="2023/01/02" stationBcdB123/station mm5/mm /rain /rainRecord 2.1 If the date is stored as a QDate (say, QDate date), give the code you would use to convert this data into the string format that is used in the XML text above? (2) 2.2 Suppose that a class named RainXml would be used to generate the XML text for all the rain data. class RainXml { public: RainXml(); RainXml getInstance(); QString writeToXml(/*passing rain data*/); private: RainXml instance; bool checkStationCode(QString stn) const; QRegularExpression re; }; This class is supposed to be implemented using a singleton design pattern. 2.2.1 The class definition code provided above does not correctly implement the classic singleton design pattern. Correct it so that it does. You are not expected to indicate the container that is used to pass rain data. (3) 8 2.2.2 Would you agree with the decision to make this class use the singleton design pattern? Explain your reason clearly and persuasively; note that marks are only allocated for the reasoning. (2) 2.3 The checkStationCode(QString stn) function from the class definition in 2.2 is used to ensure that the station code meets the correct format required, where the QString parameter is the station code that needs checking. The returned Boolean is true if the code meets requirements and false otherwise. bool RainXml::checkStationCode(QString stn) const { // add code here } The station code should meet the following requirements. -Should begin with a capital letter. -This is followed by any 2 lowercase alphabetic characters. -This is followed by the same capital letter as the initial character of the code. -The numeric part of the code is made up of any 3 digits, where the first digit cannot be zero. -There should be no other characters before or after this code. 2.3.1 Write the QRegularExpression that would be used to check codes for correctness. QRegularExpression re(/*what would you put here*/); (7) 2.3.2 Which anti-pattern would be involved if the code were not checked for meeting requirements? (1) 2.3.3 Provide the code for the checkStationCode(QString stn) function assuming that QRegularExpression re, defined in 2.3.1, is a data member of the RainXml class. (2) 2.4 The following code stub is used to generate the XML text given above. Using the required XML format from the start of Question 2, the data property from the meta-object from 1.3, and the checkStationCode() function from 2.3, complete the code where indicated by comments. Assume that each item of rain data can be obtained from the meta-object property set up in 1.3 – it returns the data in the form: StationCode:yyyy/mm/dd:mm. For example, if 10 mm of rain were received at station AagA100 on 1 January 2023, the data would be in the form AagA100::10. You are not required to provide the code for the writeToXml() function parameter or the main loop that loops through all the rain records. You may assume that for each pass through the loop, you have access to a pointer r that points to a rain record. QString RainXml::writeToXml(/*passing rain data*/) module code/101/0/2026 9 { QString xmlOutput; QXmlStreamWriter writer(&xmlOutput); // do initial setup of xml text // loop through each rain pointer named r (do not code this) { // use the meta-object to get the required data //if the station code passes the test { // set up the rain tag and its sub-tags as required } } // end xml text return xmlOutput; } (13) Question 3 [25 marks] The plan is to search the whole record of all rainfall data for a particular station’s data, and then present this data on the client screen. This search should be done in a thread. Consider the class implementation stub below (where stn is the station’s data that is required). StationThread::StationThread(/*all data*/, QString stn) : record{/*all data*/}, station{stn} {} void StationThread::doSearch(){ foreach(/*rain record in the data*/){ //get the station, date, and mm as strings if (/*this station in the data*/ == station) emit foundStation(/*date as string*/, /*mm as string*/); } } 3.1 Write the class definition for the StationThread class, remembering that it should be run as a thread. (8) 10 3.2 Consider the code below that is run when data for a particular rain station is found by the code running in the thread, where QTableWidget *tableWidget and int row have already been declared and appropriately initialised. void Client::handleFound(QString date, QString mm){ QTableWidgetItem *dateItem{new QTableWidgetItem(date)}; QTableWidgetItem *mmItem{new QTableWidgetItem(mm)}; tableWidget-setItem(row, 0, dateItem); tableWidget-setItem(row++, 1, mmItem); } Assume the following code in Client. QThread *t{new QThread}; StationThread *st{new StationThread(/*passing parameters*/)}; Write the code that would follow these declarations to get the thread running with the StationThread object, ensuring that the data is received from the running thread and passed on to the handleFound() function. (6) 3.3 Would you agree that the QTableWidget used in 3.2 is the best approach that can be used for displaying a station’s rainfall data on the client window? Give reasons for your answer. Note that marks are only allocated to your reasoning. (2) 3.4 As a way of managing a backup/restore functionality, it has been decided to subclass the QTableWidget class to implement a classic memento design pattern. The start of the class definition is provided below. class MyTableWidget: public QTableWidget { private: friend class MyTableWidgetMemento; MyTableWidget(); MyTableWidgetMemento* createMemento(); void setMemento(MyTableWidgetMemento *m); }; 3.4.1 What components usually make up the classic memento pattern, and which classes in this scenario would represent those components? (3) 3.4.2 Explain why this implementation of the classic memento patten is correct or not. Marks are only awarded for the explanation. (2) 3.5 It has been argued that cloud computing is the best way to go when it comes to managing all the rainfall data. Explain why this would be so in terms of cost and scale.