The use of interfaces in go language

In Go, the meaning of interface is no different from that of interfaces in other languages. Interface is understood as a type of specification or convention. Does a type "implement" an interface? It depends on whether this type implements all methods defined in the interface. (Recommended: go language tutorial)

1. The definition and use of interfaces.

For example,

type I interface{
    Get() int
    Put(int)
 
}

This paragraph defines an interface, which contains two functions Get and Put

Okay, one of my interfaces This interface is implemented:

type S struct {val int}
func (this *S) Get int {
    return this.val
}
func (this *S)Put(v int) {
    this.val = v
 
}

This structure S is the implementation of interface I

2, empty interface

For empty Interface interface{} is actually very similar to the concept of generics. Any type implements the empty interface.

The following is an example:

A function implements such a function:

Take any object as a parameter. If the object implements interface I, then call interface I The Get method

Many languages ​​have this logic:

function g(obj){
    if (obj is I) {
        return (I)obj.Get()
    }
 
}

This is implemented in Go:

func g(any interface{}) int {
    return any.(I).Get()
 
}

Any.(I) here is very semantic ? "Any object that implements the I interface"

3. How to write interface in Go:

Let's look at a few interface examples:

func SomeFunction(w interface{Write(string)}){
    w.Write("pizza")
 
}

In this example, the interface is directly defined in the parameter, which is very special...

func weirdFunc( i int ) interface{} {
  if i ==  0 {
    return "zero"
  }
  return i;
}

In this example, since it is possible to return string or int, the return value is set to interface , which can be seen in large numbers in Go packages.

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