program golang slices like java Stream API

go_stream_like_java.go

package main

import (
	"fmt"
	"reflect"
)

type Data struct {
	foo     string
	bar     string
	enabled bool
}

type stream struct {
	data []interface{}
}


// copy struct slice to slice of interface
func NewStream(data interface{}) *stream {
	s := reflect.ValueOf(data)
	// check
	if s.Kind() != reflect.Slice {
		panic("not slice :(")
	}
	ret := make([]interface{}, s.Len())
	for i := 0; i < s.Len(); i++ {
		ret[i] = s.Index(i).Interface()
	}
	return &stream{
		data: ret,
	}

}

// filter function
type boolFilter func(d interface{}) bool

func (s *stream) filter(f boolFilter) *stream {
	a := make([]interface{}, 0)
	for _, d := range s.data {
		if f(d) {
			a = append(a, d)
		}
	}
	s.data = a
	return s
}

func (s *stream) count() int {
	return len(s.data)
}

func main() {
	var data = []*Data{
		{
			"music",
			"on",
			true,
		},
		{
			"dota",
			"game",
			false,
		},
	}
	out := NewStream(data).filter(
		// filter data by field foo
		func(d interface{}) bool {
			return d.(*Data).foo == "music"
		}).count()

	fmt.Println(out)
}