Set and Get Function Declarations

Set and Get functions allow your objects to gain access to private variables since objects cannot access private variables directly. You can see how this is done in the Gaussian object from earlier in the lesson.

Here were the declarations for the set and get functions:

class Gaussian
{
    private:
        ...

    public:
        ...

        void setMu(float);
        void setSigma2(float);

        float getMu();
        float getSigma2();

     ....
};

And here were the function definitions:

void Gaussian::setMu (float average) {
    mu = average;
}

void Gaussian::setSigma2 (float sigma) {
    sigma2 = sigma;
}


float Gaussian::getMu () {
    return mu;
}

float Gaussian::getSigma2() {
    return sigma2;
}

The syntax for defining set or get functions is the same as any other class function (besides constructors):

return datatype Classname::functionname() {
        code to define the function;
}

In fact, get and set functions are a convention rather than a special function with a special syntax. It's traditional to name these functions getVariablename() and setVariablename() although there is no requirement to do so.

You would declare set and get functions as public so that objects could have access to these functions.

Matrix Class Set and Get Functions

Continue developing your Matrix class code.

• Use a set function to be able to modify the grid variable.
• All three private variables (gird, rows, cols) should have get functions.

Make sure to fill out the TODOs in both matrix.cpp and matrix.h

Start Quiz:

#include <iostream>
#include <vector>
#include "matrix.h"

int main () {
    
    // TODO: Nothing to do here
    
    return 0;
}

#include "matrix.h"

Matrix::Matrix() {
    std::vector <std:: vector <float> > initial_grid (10, std::vector <float>(5, 0.5));
    grid = initial_grid;
    rows = initial_grid.size();
    cols = initial_grid[0].size();

}

Matrix::Matrix(std::vector <std:: vector <float> > initial_grid) {
    grid = initial_grid;
    rows = initial_grid.size();
    cols = initial_grid[0].size();
}

/*
** TODO: Define a function setGrid()
**   INPUTS: a 2-D vector
**   OUPUTS: void
**
**   This function receives a 2-D vector reprenting a matrix, and then
**    updates the grid, rows, and cols variables
**
*/

/*
** TODO: Define getGrid(), getRows(), and getCols() functions.
**    INPUTS: None of these functions have inputs
**    OUPUTS: Each function should return its respective variable
**            For example, getRows returns the rows variable
*/

#include <vector>

class Matrix 
{

        private:

            std::vector< std::vector<float> > grid;
            std::vector<float>::size_type rows;
            std::vector<float>::size_type cols;

        public:

            // constructor function declarations
            Matrix ();
            Matrix (std::vector< std::vector<float> >);
            
            
            
            /* TODO: Declare the setGrid(), getGrid(), getRows(), 
            **       and getCols() functions. 
            **
            **  Here are the inputs and outputs of each function:
            **  setGrid()
            **  INPUTS: 2D vector
            **  OUPUTS: void
            **
            **  getGrid()
            **  INPUTS: void
            **  OUPUTS: 2D vector
            **
            **  getRows()
            **  INPUTS: void
            **  OUTPUTS: std::vector<float>::size_type
            **
            **  getCols()
            **  INPUTS: void
            **  OUPUTS: std::vector<float>::size_type
            */
};

Solution matrix.h

#include <vector>

class Matrix
{
    private:

        std::vector< std::vector<float> > grid;
        std::vector<float>::size_type rows;
        std::vector<float>::size_type cols;

    public:

        // constructor functions
        Matrix ();
        Matrix (std::vector< std::vector<float> >);

        // set functions
        void setGrid(std::vector< std::vector<float> >);

        // get functions
        std::vector< std::vector<float> > getGrid();
        std::vector<float>::size_type getRows();
        std::vector<float>::size_type getCols();
};

Solution matrix.cpp

#include "matrix.h"

Matrix::Matrix() {
    std::vector <std:: vector <float> > initial_grid (10, std::vector <float>(5, 0.5));
    grid = initial_grid;
    rows = initial_grid.size();
    cols = initial_grid[0].size();

}

Matrix::Matrix(std::vector <std:: vector <float> > initial_grid) {
    grid = initial_grid;
    rows = initial_grid.size();
    cols = initial_grid[0].size();
}


void Matrix::setGrid(std::vector< std::vector<float> > new_grid) {
    grid = new_grid;
    rows = new_grid.size();
    cols = new_grid[0].size();
}

std::vector< std::vector<float> > Matrix::getGrid() {
    return grid;
}

std::vector<float>::size_type Matrix::getRows() {
    return rows;
}

std::vector<float>::size_type Matrix::getCols() {
    return cols;
}