规则引擎对 Golang 的 struct 或者 map 进行布尔判断求值，返回 true|false 。
This package offers a parser of a simple conditions specification language (reduced set of arithmetic/logical operations). The package is mainly created for Flow-Based Programming components that require configuration to perform some operations on the data received from multiple input ports. But it can be used whereever you need externally define some logical conditions on the internal variables.
Additional credits for this package go to Handwritten Parsers & Lexers in Go by Ben Johnson on Gopher Academy blog and InfluxML package from InfluxDB repository.
package main
import (
"fmt"
"strings"
"github.com/yowenter/conditions"
)
func main() {
// Our condition to check
type people struct {
Name string
Height int32
Male bool
}
s := ` $Name == "test" AND $Height > 100 AND $Male == false`
// Parse the condition language and get expression
p := conditions.NewParser(strings.NewReader(s))
expr, err := p.Parse()
if err != nil {
fmt.Println(err)
return
// ...
}
// Evaluate expression passing data for $vars
p1 := map[string]interface{}{"Name": "test", "Height": 180, "Male": false}
r, err := conditions.Evaluate(expr, p1)
if err != nil {
fmt.Println(err)
// ...
}
fmt.Printf("Condition: `%v`, Val: `%v`, Result: `%v`\n", s, p1, r)
// use struct
var p2 = people{Name: "test", Height: 200, Male: false}
r, err = conditions.Evaluate(expr, p2)
if err != nil {
fmt.Println(err)
// ...
}
fmt.Printf("Condition: `%v`, Val: `%v`, Result: `%v`\n", s, p2, r)
// test invalid args . not map or struct.
r, err = conditions.Evaluate(expr, "")
if err != nil {
fmt.Println(err)
// ...
}
fmt.Printf("Condition: `%v`, Val: `%v`, Result: `%v`\n", s, "invalid", r)
}
Here is a diagram for a sample FBP flow (created using FlowMaker). You can see how we configure the ContextA process with a condition via IIP packet.