In this tutorial I am going to show you how to create a class, write methods for a class, create an instance of a class, and then you will learn how to call methods from that class in multiple ways.
What are classes for?
Well, classes can be used to sort or organize your code. Usually when you implement a class, it is used for separating your code so it is easier to use. A class makes it easier to call the same methods over and over again. Instead of rewriting each method, you can write it once and just include your code for next time. For instance if I want to create a class to hold the methods to solve for the volume of six shapes, then I would create a class called 'VolumeOf'
class VolumeOf end
Now that we have our class, we need to define some methods/functions. Since we want to get the volume of a cylinder, cube, sphere, pyramid, cone, and a rectangular prism; we will need to create 6 methods.
class VolumeOf
def Cylinder
end
def Cube
end
def Sphere
end
def Pyramid
end
def Cone
end
def RectangularPrism
end
end
Since the volume formulas require some user input we need to add some parameters. We can't pass any data into our methods yet because we don't have any parameters. We are going to add the 'radius' and 'height' as a parameter for the Cylinder, the 'side' as a parameter for the Cube, the 'radius' for the Sphere, the 'base' and 'height' for the Pyramid, the 'base', 'height', and 'radius' for the Cone, and the 'depth', 'height', and 'width' for the RectangularPrism. Remember when adding parameter(s) your parameter(s) need to be within a '(' and ')'. If there is more than one parameter then you need to use a comma ',' to separate them. This is what your code should look like:
class VolumeOf
def Cylinder(radius, height)
end
def Cube(side)
end
def Sphere(radius)
end
def Pyramid(base, height)
end
def Cone(base, height, radius)
end
def RectangularPrism(depth, height, width)
end
end
Now that we have our parameters in place, we need to actually code the methods. When finding the volume of a cylinder we need the radius, the height, and an approximate for pi; we will be using 3.14159 as our approximate for pi. The formula for finding the volume of a cylinder is pi * radius[squared] * height. In ruby the way we get the square of the radius is: radius * radius or we can use radius ** 2; either way will work. In this case we are going to use radius ** 2. After we get the volume we need to return the volume. Your cylinder code should look something like this:
# Gets the volume of a Cylinder def Cylinder(radius, height) # Gets an approximate for pi pi = 3.14159 # Gets the volume volume = pi * (radius ** 2) * height # Returns the volume return volume # Exit the mehtod end
We are going to do the same thing, but this time we will be using different shapes, so they will require different formulas to find the volume. The volume of a cube is side[cubed] or side * side * side. This is probably the easiest one to find the volume of. All you need to do is know the measure of one side.
# Gets the volume of a Cube def Cube(side) # Gets the cube of the side volume = (side ** 3) # Returns the volume return volume # Exit the mehtod end
The volume of a sphere is (4/3, or 1 1/3) multiplied by an approximate for pi, and we have to cube the radius. So it looks like this when we put it into code:
# Gets the volume of a Sphere def Sphere(radius) # Gets the fraction 4/3 or 1 1/3 fraction = (4 / 3) # Gets an approximate for pi pi = 3.14159 # Gets the volume volume = fraction * pi * (radius ** 3) # Return the volume return volume # Exit the method end
With a pyramid we need a fraction(1/3), the pyramid's base and pyramid's height. To get the volume all we do is multiply the fraction(1/3) by the base, then multiply that by the height. Then don't forget to return the volume.
# Gets the volume of a Pyramid def Pyramid(base, height) # Gets the fraction 1/3 fraction = (1 / 3) # Gets the volume volume = fraction * base * height # Return the volume return volume # Exit the method end
Getting the volume of a cone is similar to getting the volume of a pyramid except for the parameter we need include parameter for the radius as well as the base and height. The formula to find the volume of the cone is: (1/3) multiplied by an approximate for pi multiplied by the radius[squared] multiplied by the height. Once again don't forget that we are using 3.14159 as an approximate for pi.
# Gets the volume of a Cone def Cone(base, height, radius) # Gets the fraction 1/3 fraction = (1 / 3) # Gets an approximate for pi pi = 3.14159 # Gets the volume volume = fraction * pi * (radius ** 2) * height # Return the volume return volume # Exit the method end
Ok last one. We are going to get the volume of a rectangular prism. For this one all you need to do is get the depth, the height, and the width; then multiply them all together.
# Gets the volume of a Rectangular Prism def RectangularPrism(depth, height, width) # Getst the volume volume = depth * height * width # Return the volume return volume # Exit the mehtod end
Ok here is the full code in case you got lost somewhere:
# Gets the volumes of a Cylinder, Cube, Sphere, Pyramid, Cone, and Rectangular Prism.
class VolumeOf
# Gets the volume of a Cylinder
def Cylinder(radius, height)
# Gets an approximate for pi
pi = 3.14159
# Gets the volume
volume = pi * (radius ** 2) * height
# Returns the volume
return volume
# Exit the mehtod
end
# Gets the volume of a Cube
def Cube(side)
# Gets the cube of the side
volume = (side ** 3)
# Returns the volume
return volume
# Exit the mehtod
end
# Gets the volume of a Sphere
def Sphere(radius)
# Gets the fraction 4/3 or 1 1/3
fraction = (4 / 3)
# Gets an approximate for pi
pi = 3.14159
# Gets the volume
volume = fraction * pi * (radius ** 3)
# Return the volume
return volume
# Exit the method
end
# Gets the volume of a Pyramid
def Pyramid(base, height)
# Gets the fraction 1/3
fraction = (1 / 3)
# Gets the volume
volume = fraction * base * height
# Return the volume
return volume
# Exit the method
end
# Gets the volume of a Cone
def Cone(base, height, radius)
# Gets the fraction 1/3
fraction = (1 / 3)
# Gets an approximate for pi
pi = 3.14159
# Gets the volume
volume = fraction * pi * (radius ** 2) * height
# Return the volume
return volume
# Exit the method
end
# Gets the volume of a Rectangular Prism
def RectangularPrism(depth, height, width)
# Getst the volume
volume = depth * height * width
# Return the volume
return volume
# Exit the mehtod
end
# Exit the class
end
Ok now that we have finished coding all of the methods we are going to learn how to create a new instance of a class, and then call the methods multiple ways.
The first way I will show you will be when you only need to call a method once from a class. By that I mean, if you need to call a method more than once do NOT use Methods 1 & 2, skip ahead to Method 3.
Method 1:
# Creates a new instance of the 'VolumeOf' class # and gets the volume of a Cylinder VolumeOf.new.Cylinder(5,23)
Method 2:
# Creates a new instance of the 'VolumeOf' class # and gets the volume of a Cylinder (VolumeOf.new).Cylinder(5,23)
Method 3:
# Creates a new instance of the 'VolumeOf' class volumes = VolumeOf.new # Gets the volume of a Cylinder volumes.Cylinder(5,23)
Remember that if you want to call a method more than once, then I recommend that you use Method 3, otherwise you will have to keep defining new instances of the VolumeOf class. Ok now you should have a Basic Understanding of Classes inside of Ruby.
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