接口功能/“ cast”在golang中实际上做什么？

Question

I'm relatively new to golang, and the project I'm looking at has this sort of pattern repeated several times:

package foo

type Foo interface {
    Bar() int
}

type foo struct {
}

func (f *foo) Bar() int {
    return 42
}

func New() Foo {
    // why?
    return Foo(&foo{})
}

If I replace the returns statement in the last function with return &foo{} everything works fine as I expected... it's duck typing if I understand it correctly. So what is the point of using the Foo(...) function? Using a type as a function seems to work when you're wrapping a built in type such as int in a type that probably has methods. I'm curious as to the author's intent here. If it's covered in the language spec I was unable to find it.

Answer 1

The expression Foo(x) is a conversion . The conversion is not needed here because a *foo is assignable to a Foo . The code should be written as:

func New() Foo {
  return &foo{}
}