J7mbo

package Package3 

myStruct := Package1.NewMyStruct()
consumer := Package2.NewConsumer()

consumer.DoSomething(myStruct)

J7mbo

type consumer struct { } 

func NewConsumer() *consumer { 
    return &consumer{} 
} 

func (*consumer) DoSomething(obj interfaceToConsume) { 
    /* We can actually pass in a Package1.myStruct here! */ 
}

J7mbo

package Package2 

/* Implicit interface time! */ 
type interfaceToConsume interface { 
    SomeFunc() int 
}

J7mbo

package Package1

type myStruct struct { } 

func (*myStruct) SomeFunc() int { return 42 } 
func (*myStruct) SomeOtherFunc() string { return "42" } 

/* Factory */ 
func NewMyStruct() *myStruct { 
    return &myStruct{} 

J7mbo

type MyInterface interface { 
    MethodMustBeImplemented() 
} 

type MyStruct struct { } 

func (*MyStruct) MethodMustBeImplemented() { } // Implicit

J7mbo

interface MyInterface { } 

class MyClass implements MyInterface { } // Explicit

J7mbo

func (s MyStruct) StructFunc() { 
    if s.child == (ChildStruct{}) { 
        return 
    }
  
    fmt.Println(s.child.num) 
}

J7mbo

type MyStruct struct { 
    /* Note how s.child is not a pointer any more */ 
    child ChildStruct 
} 

func (s *MyStruct) StructFunc() { 
    if s.child != nil { 
        fmt.Println(s.child.num) 
    } 
}

J7mbo

type MyStruct struct { 
    child *ChildStruct 
} 

func (s *MyStruct) StructFunc() { 
    if s.child != nil { 
        fmt.Println(s.child.num) 
    } 
}

J7mbo

type MyStruct struct { 
    child *ChildStruct 
} 

func (s MyStruct) StructFunc() { 
    /* Here's where things go wrong */ 
    fmt.Println(s.child.num) 
} 

type ChildStruct struct {