go collection map

mapFunc.go

package main

import (
	"fmt"

	"github.com/kr/pretty"
)

type IntList []int

type T interface{}

type R interface{}

type Mapper interface {
	Map(func(T) R) Mapper
	Append(T) Mapper
}

var newFuncs = []func(v T) (Mapper, bool){
	newStringList,
	newIntList,
}

func NewList(v T) Mapper {
	for _, f := range newFuncs {
		if mapper, ok := f(v); ok {
			return mapper
		}
	}
	return nil
}

type StringList []string

func (ss StringList) Append(in T) Mapper {
	return append(ss, in.(string))
}

func newStringList(v T) (Mapper, bool) {
	switch v.(type) {
	case string:
		return make(StringList, 0), true
	default:
		return nil, false
	}
}

func newIntList(v T) (Mapper, bool) {
	switch v.(type) {
	case int:
		return make(IntList, 0), true
	default:
		return nil, false
	}
}

func (ss StringList) Map(f func(in T) R) Mapper {
	var ret Mapper
	for _, s := range ss {
		r := f(s)
		if ret == nil {
			ret = NewList(r)
		}
		if ret != nil {
			ret = ret.Append(r)
		}
	}
	return ret
}

func (is IntList) Map(f func(in T) R) Mapper {
	var ret Mapper
	for _, i := range is {
		r := f(i)
		if ret == nil {
			ret = NewList(r)
		}
		if ret != nil {
			ret = ret.Append(r)
		}
	}
	return ret
}

func (is IntList) Append(in T) Mapper {
	return append(is, in.(int))
}

func main() {

	ret := IntList{1, 2, 3, 4, 5}.
		Map(func(in T) R {
			return fmt.Sprintf("No. %d", in.(int))
		}).
		Map(func(in T) R {
			return fmt.Sprintf("This string is %s", in.(string))
		})

	pretty.Println(ret)
}