structs

structs-methods-interfaces/shapes.go

@@ -0,0 +1,32 @@
+package structsmethodsinterfaces
+
+import "math"
+
+type Shape interface {
+  Area() float64
+}
+
+type Rectangle struct {
+  Width float64
+  Height float64
+}
+
+func (r Rectangle) Area() float64 {
+  return r.Width * r.Height
+}
+
+type Circle struct {
+  Radius float64
+}
+
+func (c Circle) Area() float64 {
+  return math.Pi * c.Radius * c.Radius
+}
+
+func Perimeter(rectangle Rectangle) float64 {
+  return 2 * (rectangle.Width + rectangle.Height)
+}
+
+func Area(rectangle Rectangle) float64 {
+  return rectangle.Width * rectangle.Height
+}

structs-methods-interfaces/shapes_test.go

@@ -0,0 +1,30 @@
+package structsmethodsinterfaces
+
+import "testing"
+
+func TestPerimeter(t *testing.T) {
+  rectangle := Rectangle{10.0, 10.0}
+  got := Perimeter(rectangle)
+  want := 40.0
+
+  if got != want {
+    t.Errorf("got %.2f want %.2f", got, want)
+  }
+}
+
+func TestArea(t *testing.T) {
+  areaTests := []struct {
+    shape Shape
+    want float64
+  }{
+    {Rectangle{12, 6}, 72.0},
+    {Circle{10}, 314.1592653589793},
+  }
+
+  for _, tt := range areaTests {
+    got := tt.shape.Area()
+    if got != tt.want {
+      t.Errorf("got %g want %g", got, tt.want)
+    }
+  }
+}