georged19 / json-logic-go

Build complex rules, serialize them as JSON, and execute them in GO

json-logic-go

This parser accepts JsonLogic rules and executes them in Go.

The JsonLogic format is designed to allow you to share rules (logic) between front-end and back-end code (regardless of language difference), even to store logic along with a record in a database. JsonLogic is documented extensively at JsonLogic.com, including examples of every supported operation and a place to try out rules in your browser.

The same format can be executed in the following libraries:

• JavaScript json-logic-js
• PHP json-logic-php
• Python json-logic-py
• Ruby json-logic-ruby
• Go json-logic-go

Examples

A note about types

This is a GO interpreter of a format designed to be transmitted and stored as JSON. So it makes sense to conceptualize the rules in JSON.

Expressed in JSON, a JsonLogic rule is always one key, with an array of values.

rule := `{"==":["apples", "apples"]}`
result, err := jsonlogic.Run(rule)
if err != nil {
	fmt.Println(err)
}
fmt.Println(result)
// true

Simple

rule := `{"==":[1, 1]}`
result, err := jsonlogic.Run(rule)
if err != nil {
	fmt.Println(err)
}
fmt.Println(result)
// true

This is a simple test, equivalent to 1 == 1. A few things about the format:

1. The operator is always in the "key" position. There is only one key per JsonLogic rule.
2. The values are typically an array.
3. Each value can be a string, number, boolean, array, or null

Compound

Here we're beginning to nest rules.

rule := `{"and": [
		{ ">": [3,1] },
		{ "<": [1,3] }
	] }`
result, err := jsonlogic.Run(rule)
if err != nil {
	fmt.Println(err)
}
fmt.Println(result)
// true

Data-Driven

Obviously these rules aren't very interesting if they can only take static literal data. Typically jsonlogic.Apply will be called with a rule object and a data object however you can also use jsonlogic.Run to run a rule object without a data object. You can use the var operator to get attributes of the data object:

rule := `{ "var": ["a"] }`
data := `{ "a": 1, "b": 2 }`
result, err := jsonlogic.Apply(rule, data)
if err != nil {
	fmt.Println(err)
}
fmt.Println(result)
// 1

If you like, we support syntactic sugar on unary operators to skip the array around values:

You can also use the var operator to access an array by numeric index:

rule := `{ "var": 1 }`
data := `[ "apple", "banana", "carrot" ]`
result, err := jsonlogic.Apply(rule, data)
if err != nil {
	fmt.Println(err)
}
fmt.Println(result)
// "banana"

Here's a complex rule that mixes literals and data. The pie isn't ready to eat unless it's cooler than 110 degrees, and filled with apples.

rule := `{ "and": [
	{ "<": [ { "var": "temp" }, 110 ] },
	{ "==": [ { "var": "pie.filling" }, "apple" ] }
] }`
data := `{ "temp": 100, "pie": { "filling": "apple" } }`
result, err := jsonlogic.Apply(rule, data)
if err != nil {
	fmt.Println(err)
}
fmt.Println(result)
// true

Installation

go get github.com/GeorgeD19/json-logic-go

If that doesn't suit you, and you want to manage updates yourself, the entire library is self-contained in jsonlogic.go and you can download it straight into your project as you see fit.

curl -O https://raw.githubusercontent.com/GeorgeD19/json-logic-go/master/jsonlogic.go