Embedding interface in a struct
A struct can also have an interface incorporated in it.That struct may be used to invoke all of the embedded interface's functions.
We will see how these methods are called depends on whether the embedded interface is a named field or an unnamed/anonymous field.
1. If the embedded interface is a named field, the named interface name must be used to invoke interface methods.
2. Interface methods can be referenced to directly or via the interface name if the embedded interface is unnamed/anonymous.
Let’s see a program illustrating above points
package main
import "fmt"
type animal interface {
breathe()
walk()
}
type dog struct {
age int
}
func (d dog) breathe() {
fmt.Println("Dog breathes")
}
func (d dog) walk() {
fmt.Println("Dog walk")
}
type pet1 struct {
a animal
name string
}
type pet2 struct {
animal
name string
}
func main() {
d := dog{age: 5}
p1 := pet1{name: "Miko", a: d}
fmt.Println(p1.name)
// p1.breathe()
// p1.walk()
p1.a.breathe()
p1.a.walk()
p2 := pet2{name: "Rocky", animal: d}
fmt.Println(p1.name)
p2.breathe()
p2.walk()
p1.a.breathe()
p1.a.walk()
}
Output
Miko
Dog breathes
Dod walk
Rocky
Dog breathes
Dog walk
Dog breathes
Dog walk
Pet1 and Pet2 are two structs we defined. The animal interface is named in the pet1 struct.
type pet1 struct {
a animal
name string
}
pet2 has unnamed/anonymous animal interface embedded
type pet2 struct {
animal
name string
}
For an instance of pet1 struct we call the breathe() and walk() method like this
p1.a.breathe()
p1.a.walk()
Directly calling these methods with raise compilation error
// p1.breathe()
// p1.walk()
p1.breathe return undefined (type pet1 has no field or method breathe)
p1.walk return undefined (type pet1 has no field or method walk)
We may directly call the breathe() and walk() methods for a pet2 struct instance.
p2.breathe()
p2.walk()
We can directly access the methods of the embedded interface if the embedded interface is anonymous or unnamed.
Below is also valid and another way of called methods of unnamed/anonymous embedded interface
p2.animal.breathe()
p2.animal.walk()
Also, the embedded interface, i.e. animal, is initialised with a type implementing it, i.e. dog, when either the pet1 or pet2 struct is created.
p1 := pet1{name: "Miko", a: d}
p2 := pet2{name: "Rocky", animal: d}
If we don't initialise the embedded interface animal, it will be set to the interface's zero value, which is nil. Calling the breathe() and walk() methods on such a pet1 or pet2 struct instance will result in a panic.
Check out this article - Compile Time Polymorphism
Frequently Asked Questions
What are embedded interfaces?
The dynamic possibilities of embedded interfaces are the same as when the same interfaces are accessible via Tempo or sites. They vary from Tempo and sites in that they lack the surrounding navigation bar and backdrop, letting the host web page to offer its own navigation.
What is embedding in Golang?
Support for embedding files and directories into the programme binary at build time without the use of an external tool is one of the most eagerly awaited features of Go 1.16.
This functionality is also known as go:embed, and it takes its name from the compiler directive that enables it.
What is polymorphism in Golang?
Polymorphism refers to a message's ability to appear in several forms.Polymorphism is one of the most significant characteristics of Object-Oriented Programming, and it may be performed at runtime or at compile time.
What is dependency injection in Golang?
Dependency injection is a method that allows an item to receive dependencies from other objects. The receiving object is usually referred to as a client, whereas the passed-in ('injected') item is referred to as a service.
Conclusion
If you made till here, that means you enjoyed reading it. The article extensively covers the implementation of interface embedding in golang. You might be interested in articles such as Basic of Json with Golang, Race condition in Golang and Function as a field in Golang.
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