Implementing MVC

Question

I am working on implementing code using MVC for my class however I am running into an error I cant seem to figure out. The only parts of the assignment I am supposed to change are Model, View, and Controller so the rest of the classes were already completed for us.

When I run the code I get an error in the controller saying:

"error: incompatible types: Student cannot be converted to String view.DisplayOnButton(model.getInfoForStudent(0), 0);"

How do I fix this?

Here is what I have:

Controller -

public class Controller { Model model; View view; public Controller(Model model, View view) { this.model = model; this.view = view; SetViewFromModel(); } public void SetViewFromModel() { view.DisplayOnButton(model.getInfoForStudent(0), 0); view.DisplayOnButton(model.getInfoForStudent(1), 1); view.DisplayOnButton(model.getInfoForStudent(2), 2); } }

Model -

 public class Model { ArrayList<Student> sts = new ArrayList<>(); public Model() { //creates 3 students MailAddress addr1 = new MailAddress("107 W College Avenue", "State College", "PA", 16801); Student st1 = new Student("Emily", "Smith", 20, addr1); MailAddress addr2 = new MailAddress("200 W College Avenue", "State College", "PA", 16801); Student st2 = new Student("Mary", "Doe", 20, addr2); MailAddress addr3 = new MailAddress("300 W College Avenue", "State College", "PA", 16801); Student st3 = new Student("John", "Doe", 20, addr3); //add them to the array of students sts.add(st1); sts.add(st2); sts.add(st3); } public Student getInfoForStudent (int studentIndex) { return sts.get(studentIndex); } }

View -

public void DisplayOnButton(String infoToDisplay, int onButton) { mf.getIp().DisplayOnButton(infoToDisplay, onButton); }

can you put your stacktrace (the error that you get)? there you should have the information about the line that caused the error — vmrvictor
– vmrvictor, Commented Oct 6, 2018 at 6:15
Call toString() on student objects? But please read minimal reproducible example and enhance your question accordingly. Your question is missing various details we would need to help you. — GhostCat
– GhostCat, Commented Oct 6, 2018 at 6:17
DisplayOnButton has a requirement that the parameter must be a String, either change the parameter type or pass in a String — MadProgrammer
– MadProgrammer, Commented Oct 6, 2018 at 6:25

vmrvictor · Accepted Answer · 2018-10-06 06:54:04Z

your method DisplayOnButton is expecting a String and you are passing an Student, you will have to convert your getInfoForStudent to return a String or convert the Student to String.

I recommend you to overwrite toString() for your mail and student so it creates an String with the information that you expect.

for example:

public class Student { private final String name; private final String surname; private final int age; private final MailAddress mailAddress; public Student(String name, String surname, int age, MailAddress mailAddress) { this.name = name; this.surname = surname; this.age = age; this.mailAddress=mailAddress; } @Override public String toString() { return String.format("name: %s surname:%s age:%d mail address:%s", name, surname, age, mailAddress); } }

you will have to do something similar for mailAddress, so then your getInfoForStudent looks like that:

 public String getInfoForStudent (int studentIndex) { return sts.get(studentIndex).toString(); }

this getInfo() is the toString(), so you can change return sts.get(studentIndex) to return sts.get(studentIndex).getInfo()
The Student class is already completed for us in this assignment and its done in a similar fashion as you have it and returns a String. when I try return sts.get(studentIndex).getInfo() I get an error next to the line of code saying "String cannot be converted to student"
so use this method to get a String with the information of your Students

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