Node/Extend

When you want to make adjustments to an existing node’s implementation
Tags:

Use cases:

  • Few isolated changes to an existing node
  • Wrap a CRUD node but customize editing operations, actions or notifications

Special notes

  • If [Reflect]({ { < relref “reflect” > } } ) was a cake and [Basic]({ { < relref “basic” > } } ) was the plate under the cake, then Extend would be the frosting.
  • Extend is exactly like Basic but let’s you delegate anything to another node. So most of Basic's documentation also applies here.

Reflect with one exception

package demo

import "fmt"

type Bird struct {
	Name string
	X    int
	Y    int
}

func (b *Bird) GetCoordinates() string {
	return fmt.Sprintf("%d,%d", b.X, b.Y)
}



class Bird():

    def __init__(self, name, x, y):
        self.name = name
        self.x = x
        self.y = y

    def coordinates(self):
        return f'{self.x},{self.y}'

module bird {
	namespace "freeconf.org";
	prefix "b";

	leaf name {
		type string;
	}

	leaf location {
		config false;
		type string {
			pattern "[0-9.]+,[0-9.]+";
		}
	}
}


package demo

import (
	"github.com/freeconf/yang/node"
	"github.com/freeconf/yang/nodeutil"
	"github.com/freeconf/yang/val"
)

func manage(b *Bird) node.Node {
	return &nodeutil.Extend{
		Base: nodeutil.ReflectChild(b), // handles Name
		OnField: func(p node.Node, r node.FieldRequest, hnd *node.ValueHandle) error {
			switch r.Meta.Ident() {
			case "location":
				hnd.Val = val.String(b.GetCoordinates())
			default:
				// delegates to ReflectChild for name
				return p.Field(r, hnd)
			}
			return nil
		},
	}
}


from freeconf import nodeutil, val

def manage_bird(bird):
    base = nodeutil.Node(bird)
    
    def on_field(parent, req, write_val):
        if req.meta.ident == "location":
            return val.Val(bird.coordinates())
        return parent.field(req, write_val)
    
    return nodeutil.Extend(base, on_field=on_field)

Addition Files

file: manage_test.go

package demo

import (
	"testing"

	"github.com/freeconf/yang/fc"
	"github.com/freeconf/yang/node"
	"github.com/freeconf/yang/nodeutil"
	"github.com/freeconf/yang/parser"
	"github.com/freeconf/yang/source"
)

func TestManage(t *testing.T) {
	b := &Bird{Name: "sparrow", X: 99, Y: 1000}
	ypath := source.Dir(".")
	m := parser.RequireModule(ypath, "bird")
	bwsr := node.NewBrowser(m, manage(b))

	root := bwsr.Root()
	defer root.Release()
	actual, err := nodeutil.WriteJSON(root)
	fc.AssertEqual(t, nil, err)
	fc.AssertEqual(t, `{"name":"sparrow","location":"99,1000"}`, actual)
}

file: test_manage.py

#!/usr/bin/env python3
import unittest 
from freeconf import parser, nodeutil, source, node
from manage import manage_bird
from bird import Bird 

class TestManage(unittest.TestCase):

    def test_manage(self):
        app = Bird("sparrow", 99, 1000)
        ypath = source.path('..')
        m = parser.load_module_file(ypath, 'bird')
        mgmt = manage_bird(app)
        bwsr = node.Browser(m, mgmt)
        root = bwsr.root()
        try:
            actual = nodeutil.json_write_str(root)
            self.assertEqual('{"name":"sparrow","location":"99,1000"}', actual)
        finally:
            root.release()

if __name__ == '__main__':
    unittest.main()