Dave Drohan (SETU)

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Writing your own methods (1)

In this step, you will work on reproducing the code examples 5.2 to 5.5 inclusive from your lectures.

Example 5.2

Create a new Processing sketch in your workspace and call it Example_5_2.

Write a method called drawRedSquare that takes no parameters.

The return type for this method is void.

The method body should include the following processing:

• set the fill colour to red.
• draw a square with a length of 60 pixels at the coordinates (70,70).

The drawRedSquare method should be called from the draw() method.

Run your code; a red square should be drawn on the display window.

The solution code is:

void setup()
{
  size(200,200);
  background(20,70,105);
}

void draw()
{
   drawRedSquare();
}

void drawRedSquare()
{
  fill(255,0,0);
  rect(70,70,60,60);
}

Example 5.3

Create a new Processing sketch in your workspace and call it Example_5_3.

Write a method called drawRedSquare that takes one parameter of type int. This parameter will be used to set the length of the square.

The return type for this method is void.

The method body should include the following processing:

• set the fill colour to red.
• draw a square at the coordinates (70,70) and use the int parameter to determine the length of the square.

The drawRedSquare method should be called from the draw() method, passing the value 60 as its argument.

Run your code; a red square should be drawn on the display window.

The solution code is:

void setup()
{
  size(200,200);
  background(20,70,105);
}

void draw()
{
   drawRedSquare(60);
}

void drawRedSquare(int length)
{
  fill(255,0,0);
  rect(70,70,length, length);
}

Example 5.4

Create a new Processing sketch in your workspace and call it Example_5_4.

Write a method called drawRedSquare that takes three parameters. Each of the parameters is of type int:

• parameter one represents the length of the square.

• parameter two represents the xCoordinate of the square.

• parameter three represents the yCoordinate of the square.

The return type for this method is void.

The method body should include the following processing:

• set the fill colour to red.

• draw a square where:

  • the length of the square is the value passed as the first parameter into the method.

  • its coordinates are those that were passed as the second and third arguments to the method.

The drawRedSquare method should be called from the draw() method, passing the values 60, 70, 40 as its arguments.

Run your code; a red square should be drawn on the display window.

The solution code is:

void setup()
{
  size(200,200);
  background(20,70,105);
}

void draw()
{
   drawRedSquare(60,70,40);
}

void drawRedSquare(int length, int xCoord, int yCoord)
{
  fill(255,0,0);
  rect(xCoord,yCoord,length, length);
}

Example 5.5

Create a new Processing sketch in your workspace and call it Example_5_5.

Enter the following code into the sketch (don’t cut and paste, write it out):

void setup() 
{ 
    size(200,200); 
    background(20,70,105); 
}

void draw()
{
    for (int i = 1; i < 7; i++)
    {
        drawRedSquare(25, i*25, i*20);
    }
}

void drawRedSquare(int length, int xCoord, int yCoord)
{
    fill(255,0,0);
    rect(xCoord,yCoord, length, length);
}

This code calls the drawRedSquare method multiple times (using a for loop).

Run your code. Does it work as you would expect? Are 6 red squares drawn on the display window?

Now try re-write the for loop so that it is a while loop. Run and test your code again. There should be no changes in the display window.