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A Week with Go, Day 4

Day 4 was spent learning about Go's take on object oriented programming, which I found to be a refreshing change from the likes of Java and C#. It's not type-focused; instead of relying on an object's type to know whether or not it offer certain functionality, the object will generally implement an interface. This mindset is not dissimilar to good JavaScript programming where feature detection is preferred over browser sniffing. The code doesn't care what something is (browser/object), just what it can do (functionality/interface).

The word "object" is probably a bit misleading since Go doesn't really have them in the traditional sense. There's no need to write a class definition as in Java, nor to instantiate an object literal like JavaScript. The programmer specifies a set of functions and Go's compiler deduces the relationships.
type Rectangle struct {
    width  float
    height float

func (r *Rectangle) Area() float {
    return r.width * r.height

func (r *Rectangle) Perimeter() float {
    return r.width*2 + r.height*2

func main() {
    r := new(Rectangle)
Here the Rectangle "object" is a pointer to a structure consisting of two floats. The Area() function can be applied as a method against any Rectangle to calculate an area, and the Perimeter() function can be applied to calculate the perimeter.

If I were to later specify the interface Shape which dictated an Area() float method and Perimeter() float method, then any Rectangle instances will automatically implement it. The compiler knows a Shape can have its area and perimeter calculated. A Rectangle can have its area and perimeter calculated; therefore, it must be a Shape.
type Shape interface {
    Area() float
    Perimeter() float
I appreciate Go's rejection of Java-style type-masturbation and focus on functionality. After all, code is a liability, functionality is an asset. It looks like Go will let me focus more on writing code which provides functionality instead of code that specifies type hierarchies rivaling Jesus' lineage in the book of Matthew.

Feel free to share your impressions of Go in the comments below and come back tomorrow for the final day's entry in the series. If you're interested, here's my shapes code with with Rectangle and Circle objects.


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