vectors and objects

This is a discussion on vectors and objects within the C++ Programming forums, part of the General Programming Boards category; hi...i have a class that i made called Apartment. i need to create a vector and call the class objects. ...

  1. #1
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    vectors and objects

    hi...i have a class that i made called Apartment. i need to create a vector and call the class objects. i'm trying to see how to do it but my book and a lot of websites barely have any info. i have objects inside the Apartment class: dispInfo and getName.

    so far i'm declaring the vector like this:

    Code:
    vector<int> vector_one;
    vector<Apartment> apt;
    int user_input;
    
    	for(i=0; i<user_input; i++)
    		apt.push_back(i);
    which does not work. however when i use
    Code:
    		vector_one.push_back(i);
    which runs fine.

    how can i get apt to work like how vector_one works. also, how can i call the objects inside apt?

    thanks

  2. #2
    Registered User hk_mp5kpdw's Avatar
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    You need to call the Apartment constructor to create an Apartment object and push it onto the vector. Without seeing your code for the Apartment class, I could only guess you would be trying to do something like:

    Code:
    vector<Apartment> apt;
    int user_input;
    
    for(i=0; i<user_input; i++)
        apt.push_back(Apartment());
    Of course that would only work if your Apartment class had an appropriate default constructor.

    Code:
    vector_one.push_back(i);
    That works because vector_one is a vector<int> and you are pushing ints onto that vector.

    Code:
    apt.push_back(i);
    That does not work because you are pushing an int onto a vector that expects Apartment objects. Note: Actually that could work if you had a constructor that accepted an int as an argument during construction as a conversion would be made from apt.push_back(i) into apt.push_back(Apartment(i)) so you should be careful. I.e.:

    Code:
    class Test
    {
    public:
        int data;
        Test(int val=0) : data(val) {}
    };
    
    ...
    
    vector<Test> testVect;
    
    ...
    
    testVect.push_back(Test());  // Pushes a Test object with data=0 onto vector
    testVect.push_back(Test(2)); // Pushes a Test object with data=2 onto vector
    testVect.push_back(4);       // Pushes a Test object with data=4 onto vector
    To avoid accidentally doing that you must use the keyword 'explicit', i.e.

    Code:
    class Test
    {
    public:
        int data;
        explicit Test(int val=0) : data(val) {}
    };
    
    ...
    
    testVect.push_back(4);  // Error attempting to implicitly convert 4 into Test(4)
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

  3. #3
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    thanks.
    Code:
    one.push_back(Apartment());
    calls up the default constructor. how can i call the set member functions (or methods) inside the class apartment?

  4. #4
    Registered User hk_mp5kpdw's Avatar
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    After it has been constructed and pushed onto the vector?

    Code:
    class Person
    {
        string fname, lname;
        int age;
    public:
        Person() {}
        void SetAge( int _age ) { age = _age; }
        void SetFirstName( string first ) { fname = first; }
        void SetLastName( string last ) { lname = last; }
        int GetAge() const { return age; }
        string GetFirstName() const { return fname; }
        string GetLastName() const { return lname; }
    };
    
    vector<Person> person;
    
    // Push a Person object onto the vector
    person.push_back(Person);
    
    // Call the member functions for that object on the vector
    person[0].SetFirstName(string("John"));
    person[0].SetLastName(string("Doe"));
    person[0].SetAge(28);
    
    cout << "Name: " << person[0].GetFirstName() << ' ' << person[0].GetLastName()
         << " Age: " << person[0].GetAge() << endl;
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

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