Different structs implementing same interface in Golang

Question

I have an interface

type Shape interface {
    area() float32
    circumference() float32
}

I want to create different shapes such as a circle and a rectangle, for the circle I need to know the radius, and for the rectangle the 2 sides. So the code for each is like the following:

type DataCircle struct {
     radius float
}

(*DataCircle) area() float32 {
    return 3.14 * DataCircle.radius * DataCircle.radius;
}

(*DataCircle) circumference() float32 {
    return 2 * 3.14 * DataCircle.radius;
}

Similarly we have code for a rectangle which implement the interface Shape, with the following struct

type DataRectangle struct {
     side1 float
     side2 float
}

I want to create many different Rectangles and many different Circles, each one has different radius/sides. In the end I want to put them in a single array and be able to do something like the following

for _, shape := range all_shapes_in_array {
    fmt.Printf("%f %f", shape.area(), shape.circumference())
}

In a normal object oriented language this is pretty straight forward, but how do I do it in Golang?

Jack Gore · Accepted Answer · 2019-04-12 20:45:05Z

2

As long as your DataCircle and DataRectangle structs implement the Shape interface you will be able to create an array/slice of type Shape and iterate through it.

If you already have them implementing Shape then all you need to do is this:

circle1 := &DataCircle{1}
circle2 := &DataCircle{2}
rec1 := &DataRectangle{1, 1}
rec2 := &DataRectangle{4, 1}

all_shapes_in_array := []Shape{circle1, circle2, rec1, rec2}
for _, shape := range all_shapes_in_array {
    fmt.Printf("%f %f", shape.area(), shape.circumference())
}

And it will work as expected.

answered Apr 12, 2019 at 20:45

Jack Gore

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1 Comment

jdoe Over a year ago

Thanks. The problems stemmed from the use of *DataCircle in my code, didn't know * made a difference.

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