Golang，Go：具有返回接口的映射？

Question

http://golang.org/pkg/sort/

This is from Go example.

 // OrderedBy returns a Sorter that sorts using the less functions, in order.
// Call its Sort method to sort the data.
func OrderedBy(less ...lessFunc) *multiSorter {
    return &multiSorter{
        changes: changes,
        less:    less,
    }
}

What does this do by colon? Is it mapping? Is it closure? Too much new syntax here. What should I read to understand this syntax in Go?

Answer 1

It's a factory function, creating and initialising a struct of type multisorter:

https://sites.google.com/site/gopatterns/object-oriented/constructors

Additionally, Go "constructors" can be written succinctly using initializers within a factory function:

function NewMatrix(rows, cols, int) *matrix {
    return &matrix{rows, cols, make([]float, rows*cols)}
}

Also, it is using named parameters when initialising:

http://www.golang-book.com/9

This allocates memory for all the fields, sets each of them to their zero value and returns a pointer. (Circle) More often we want to give each of the fields a value. We can do this in two ways. Like this:

c := Circle{x: 0, y: 0, r: 5}

Answer 2

The `less ...lessFunc` in the func declaration means:

any number of parameters, each of type `lessFunc` can be passed here, and will be stored in the slice `less`

So it creates a `multiSorter` struct, which supports the sort interface, and calling the sort method from that interface (and implemented by multiSorter) will cause the object to use each lessFunc in turn while sorting

Does this make sense? I can expand more if needed...