DDT allows building custom decision trees based in a set of defined rules, programmatically or from json.
When making a decision, it allows adding a pre-processing stage to the input before comparing it with the following possible branches of the tree.
One of the default preprocessing functions in ddt is calling a method of a struct (CallStructMethod) and getting the attribute of a struct (GetStructAttribute) using reflection.
Use a struct as input of the tree and pre-process data before comparing with the next level of nodes.
In this example we use some methods and attributes of the user struct.
package main
import (
"fmt"
"github.com/sgrodriguez/ddt"
"github.com/sgrodriguez/ddt/compare"
"github.com/sgrodriguez/ddt/function"
"github.com/sgrodriguez/ddt/value"
)
type user struct {
Age int
FirstName string
LastName string
}
func (u *user) UnderAge() bool {
return u.Age < 18
}
func (u *user) FullName() string {
return u.FirstName + " " + u.LastName
}
func main() {
node6 := &ddt.Node{
ID: 6,
ParentID: 2,
ValueToCompare: &value.Value{Type: value.Int, Value: 30},
Result: &value.Value{Type: value.String, Value: "node6"},
Comparer: &compare.Greater{},
}
node5 := &ddt.Node{
ID: 5,
ParentID: 2,
ValueToCompare: &value.Value{Type: value.Int, Value: 30},
Result: &value.Value{Type: value.String, Value: "node5"},
Comparer: &compare.Lesser{Equal: true},
}
node3 := &ddt.Node{
ID: 3,
ParentID: 1,
ValueToCompare: &value.Value{Type: value.String, Value: "SANTIAGO LUCIA"},
Result: &value.Value{Type: value.String, Value: "node3"},
Comparer: &compare.Equal{},
}
node4 := &ddt.Node{
ID: 4,
ParentID: 1,
ValueToCompare: &value.Value{Type: value.String, Value: "LUCIA SANTIAGO"},
Result: &value.Value{Type: value.String, Value: "node4"},
Comparer: &compare.Equal{},
}
node1 := &ddt.Node{
ID: 1,
ParentID: 0,
Children: []*ddt.Node{node3, node4},
ValueToCompare: &value.Value{Type: value.Bool, Value: true},
PreProcessArgs: []*value.Value{{Type: value.String, Value: "FullName"}},
PreProcessFn: function.PreProcessFn{Function: function.CallStructMethod, Name: "CallStructMethod"},
Comparer: &compare.Equal{},
}
node2 := &ddt.Node{
ID: 2,
ParentID: 0,
Children: []*ddt.Node{node5, node6},
ValueToCompare: &value.Value{Type: value.Bool, Value: false},
Comparer: &compare.Equal{},
PreProcessArgs: []*value.Value{{Type: value.String, Value: "Age"}},
PreProcessFn: function.PreProcessFn{Function: function.GetStructAttribute, Name: "GetStructAttribute"},
}
root := &ddt.Node{
Children: []*ddt.Node{node1, node2},
PreProcessArgs: []*value.Value{{Type: value.String, Value: "UnderAge"}},
PreProcessFn: function.PreProcessFn{Function: function.CallStructMethod, Name: "CallStructMethod"},
ID: 0,
ParentID: -1,
}
userTree, err := ddt.NewTree("userTree", root)
if err != nil {
panic(err)
}
result, err := ddt.ResolveTree(userTree, &user{Age: 12, FirstName: "SANTIAGO", LastName: "LUCIA"})
if err != nil {
panic(err)
}
// result node3
fmt.Println(result.(string))
}package main
import (
"encoding/json"
"fmt"
"github.com/sgrodriguez/ddt"
)
type user struct {
Age int
FirstName string
LastName string
}
func (u *user) UnderAge() bool {
return u.Age < 18
}
func (u *user) FullName() string {
return u.FirstName + " " + u.LastName
}
func main() {
// define empty tree
tree, err := ddt.NewTree("newTree", &ddt.Node{ID: 0, ParentID: -1})
if err != nil {
panic(err)
}
treeFromJson := []byte(`
{
"nodes":[
{
"preProcessFnName":"CallStructMethod",
"id":0,
"parentId":-1,
"preProcessFnArgs":[
{
"Value":"UnderAge",
"Type":"string"
}
]
},
{
"preProcessFnName":"CallStructMethod",
"id":1,
"parentId":0,
"preProcessFnArgs":[
{
"Value":"FullName",
"Type":"string"
}
],
"comparer":{
"type":"eq"
},
"valueToCompare":{
"Value":true,
"Type":"bool"
}
},
{
"preProcessFnName":"GetStructAttribute",
"id":2,
"parentId":0,
"preProcessFnArgs":[
{
"Value":"Age",
"Type":"string"
}
],
"comparer":{
"type":"eq"
},
"valueToCompare":{
"Value":false,
"Type":"bool"
}
},
{
"preProcessFnName":"",
"id":3,
"parentId":1,
"comparer":{
"type":"eq"
},
"valueToCompare":{
"Value":"SANTIAGO LUCIA",
"Type":"string"
},
"result":{
"Value":"node3",
"Type":"string"
}
},
{
"preProcessFnName":"",
"id":4,
"parentId":1,
"comparer":{
"type":"eq"
},
"valueToCompare":{
"Value":"LUCIA SANTIAGO",
"Type":"string"
},
"result":{
"Value":"node4",
"Type":"string"
}
},
{
"preProcessFnName":"",
"id":5,
"parentId":2,
"comparer":{
"type":"lt",
"equal":true
},
"valueToCompare":{
"Value":30,
"Type":"int"
},
"result":{
"Value":"node5",
"Type":"string"
}
},
{
"preProcessFnName":"",
"id":6,
"parentId":2,
"comparer":{
"type":"gt",
"equal":false
},
"valueToCompare":{
"Value":30,
"Type":"int"
},
"result":{
"Value":"node6",
"Type":"string"
}
}
],
"name":"userTree"
}`)
err = json.Unmarshal(treeFromJson, tree)
if err != nil {
panic(err)
}
result, err := ddt.ResolveTree(tree, &user{Age: 12, FirstName: "SANTIAGO", LastName: "LUCIA"})
if err != nil {
panic(err)
}
// result node3
fmt.Println(result.(string))
treeByte, err := json.Marshal(tree)
fmt.Println(string(treeByte))
}Create a simple tree using only basic types.
package main
import (
"fmt"
"github.com/sgrodriguez/ddt"
"github.com/sgrodriguez/ddt/compare"
"github.com/sgrodriguez/ddt/value"
)
func main() {
leaf1 := ddt.Node{
ID: 1,
ParentID: 0,
ValueToCompare: &value.Value{Value: int64(60), Type: value.Int64},
Comparer: &compare.Greater{},
Result: &value.Value{Value: "prize1", Type: value.String},
}
leaf11 := ddt.Node{
ID: 3,
ParentID: 2,
ValueToCompare: &value.Value{Value: int64(30), Type: value.Int64},
Comparer: &compare.Equal{},
Result: &value.Value{Value: "prize2", Type: value.String},
}
leaf12 := ddt.Node{
ID: 4,
ParentID: 2,
ValueToCompare: &value.Value{Value: int64(30), Type: value.Int64},
Comparer: &compare.Greater{},
Result: &value.Value{Value: "prize3", Type: value.String},
}
leaf13 := ddt.Node{
ID: 5,
ParentID: 2,
ValueToCompare: &value.Value{Value: int64(30), Type: value.Int64},
Comparer: &compare.Lesser{},
Result: &value.Value{Value: "prize4", Type: value.String},
}
node1 := ddt.Node{
Children: []*ddt.Node{&leaf11, &leaf12, &leaf13},
ID: 2,
ParentID: 0,
ValueToCompare: &value.Value{Value: int64(60), Type: value.Int64},
Comparer: &compare.Lesser{Equal: true},
}
root := ddt.Node{
ID: 0,
ParentID: -1,
Children: []*ddt.Node{&node1, &leaf1},
}
simpleTree, err := ddt.NewTree("simpleTree", &root)
if err != nil {
panic(err)
}
result, err := ddt.ResolveTree(simpleTree,int64(15))
if err != nil {
panic(err)
}
fmt.Println(result.(string))
}Create or modify the simple tree from json
package main
import (
"encoding/json"
"fmt"
"github.com/sgrodriguez/ddt"
)
func main() {
// define empty tree
tree, err := ddt.NewTree("newTree", &ddt.Node{ID: 0, ParentID: -1})
if err != nil {
panic(err)
}
treeFromJson := []byte(`
{
"nodes":[
{
"preProcessFnName":"",
"id":0,
"parentId":-1
},
{
"preProcessFnName":"",
"id":2,
"parentId":0,
"comparer":{
"type":"lt",
"equal":true
},
"valueToCompare":{
"Value":60,
"Type":"int64"
}
},
{
"preProcessFnName":"",
"id":1,
"parentId":0,
"comparer":{
"type":"gt",
"equal":false
},
"valueToCompare":{
"Value":60,
"Type":"int64"
},
"result":{
"Value":"prize1",
"Type":"string"
}
},
{
"preProcessFnName":"",
"id":3,
"parentId":2,
"comparer":{
"type":"eq"
},
"valueToCompare":{
"Value":30,
"Type":"int64"
},
"result":{
"Value":"prize2",
"Type":"string"
}
},
{
"preProcessFnName":"",
"id":4,
"parentId":2,
"comparer":{
"type":"gt",
"equal":false
},
"valueToCompare":{
"Value":30,
"Type":"int64"
},
"result":{
"Value":"prize3",
"Type":"string"
}
},
{
"preProcessFnName":"",
"id":5,
"parentId":2,
"comparer":{
"type":"lt",
"equal":false
},
"valueToCompare":{
"Value":30,
"Type":"int64"
},
"result":{
"Value":"prize4",
"Type":"string"
}
}
],
"name":"simpleTree"
}`)
err = json.Unmarshal(treeFromJson, tree)
if err != nil {
panic(err)
}
result, err := ddt.ResolveTree(tree, int64(15))
if err != nil {
panic(err)
}
// result prize4
fmt.Println(result.(string))
// change some property of the tree for example the result of prize4
modifiedTree := []byte(`{"nodes":[{"preProcessFnName":"","id":0,"parentId":-1},{"preProcessFnName":"","id":2,"parentId":0,"comparer":{"type":"lt","equal":true},"valueToCompare":{"Value":60,"Type":"int64"}},{"preProcessFnName":"","id":1,"parentId":0,"comparer":{"type":"gt","equal":false},"valueToCompare":{"Value":60,"Type":"int64"},"result":{"Value":"prize1","Type":"string"}},{"preProcessFnName":"","id":3,"parentId":2,"comparer":{"type":"eq"},"valueToCompare":{"Value":30,"Type":"int64"},"result":{"Value":"prize2","Type":"string"}},{"preProcessFnName":"","id":4,"parentId":2,"comparer":{"type":"gt","equal":false},"valueToCompare":{"Value":30,"Type":"int64"},"result":{"Value":"prize3","Type":"string"}},{"preProcessFnName":"","id":5,"parentId":2,"comparer":{"type":"lt","equal":false},"valueToCompare":{"Value":30,"Type":"int64"},"result":{"Value": 420,"Type":"int64"}}],"name":"simpleTree"}`)
err = json.Unmarshal(modifiedTree, tree)
if err != nil {
panic(err)
}
result, err = ddt.ResolveTree(tree, int64(15))
if err != nil {
panic(err)
}
// result 420
fmt.Println(result.(int64))
}- ID: id of the node, root node must have 0.
- ParentID: parent id, root node must have -1.
- Result: if the node is leaf and is the next node of the tree, this is the result.
- Comparer.
- ValueToCompare: value
- PreProcessFn: function to pre-process the input before comparing.
- PreProcessArgs.
Basic types available for comparing, result and as PreProcessArgs.
- Int
- Int64
- Bool
- String
- Float64
- Greater (or Equal)
- Lesser (or Equal)
- Equal
Functions to pre-process the input before comparing with the next level of the tree.
- CallStructMethod
- GetStructAttribute