Go JsonLogic

Implementation of JsonLogic in Go Lang.

What's JsonLogic?

JsonLogic is a DSL to write logic decisions in JSON. It's has a great specification and is very simple to learn. The official website has great documentation with examples.

How to use it

The use of this library is very straightforward. Here's a simple example:

package main

import (
    "bytes"
    "fmt"
    "strings"

    "github.com/diegoholiveira/jsonlogic/v3"
)

func main() {
    logic := strings.NewReader(`{"==": [1, 1]}`)
    data := strings.NewReader(`{}`)

    var result bytes.Buffer

    jsonlogic.Apply(logic, data, &result)

    fmt.Println(result.String())
}

This will output true in your console.

Here's another example, but this time using variables passed in the data parameter:

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "strings"

    "github.com/diegoholiveira/jsonlogic/v3"
)

type (
    User struct {
        Name     string `json:"name"`
        Age      int    `json:"age"`
        Location string `json:"location"`
    }

    Users []User
)

func main() {
    logic := strings.NewReader(`{
        "filter": [
            {"var": "users"},
            {">=": [
                {"var": ".age"},
                18
            ]}
        ]
    }`)

    data := strings.NewReader(`{
        "users": [
            {"name": "Diego", "age": 33, "location": "Florianópolis"},
            {"name": "Jack", "age": 12, "location": "London"},
            {"name": "Pedro", "age": 19, "location": "Lisbon"},
            {"name": "Leopoldina", "age": 30, "location": "Rio de Janeiro"}
        ]
    }`)

    var result bytes.Buffer

    err := jsonlogic.Apply(logic, data, &result)
    if err != nil {
        fmt.Println(err.Error())

        return
    }

    var users Users

    decoder := json.NewDecoder(&result)
    decoder.Decode(&users)

    for _, user := range users {
        fmt.Printf("    - %s\n", user.Name)
    }
}

If you have a function you want to expose as a JsonLogic operation, you can use:

package main

import (
    "bytes"
    "fmt"
    "strings"

    "github.com/diegoholiveira/jsonlogic/v3"
)

func main() {
    // add a new operator "strlen" for get string length
    jsonlogic.AddOperator("strlen", func(values, data interface{}) interface{} {
        v, ok := values.(string)
        if ok {
            return len(v)
        }
        return 0
    })

    logic := strings.NewReader(`{ "strlen": { "var": "foo" } }`)
    data := strings.NewReader(`{"foo": "bar"}`)

    var result bytes.Buffer

    jsonlogic.Apply(logic, data, &result)

    fmt.Println(result.String()) // the string length of "bar" is 3
}

If you want to get the JsonLogic used, with the variables replaced by their values:

package main

import (
    "fmt"
    "encoding/json"

    "github.com/diegoholiveira/jsonlogic/v3"
)

func main() {
    logic := json.RawMessage(`{ "==":[{ "var":"foo" }, true] }`)
    data := json.RawMessage(`{"foo": "false"}`)

    result, err := jsonlogic.GetJsonLogicWithSolvedVars(logic, data)

    if err != nil {
        fmt.Println(err)
    }

    fmt.Println(string(result)) // will output { "==":[false, true] }
}

License

This project is licensed under the MIT License - see LICENSE for details.