Golang implementation of JsonLogic (jsonlogic.com), which is an abstract syntax tree (AST) represented as a JSON object.
Custom operators are supported.
Rules Validation is supported.
var rule, data interface{}
json.Unmarshal([]byte(`
{"if": [
{"<": [{"var":"temp"}, 0] }, "freezing",
{"<": [{"var":"temp"}, 100] }, "liquid",
"gas"
]}
`), &rule)
json.Unmarshal([]byte(`{"temp":55}`), &data)
got, err := jsonlogic.Apply(rule, data)
if err != nil {
// handle error
}
fmt.Println(got)
// Output: liquidYou can add your own operator to jsonlogic by implementing jsonlogic.Operator interface and registering it to a jsonlogic instance.
The following example shows how to implement a greatest common divisor (gcd) operator.
// gcd operator
type gcd struct{}
// Operate implements `jsonlogic.Operator`
func (gcd) Operate(applier jsonlogic.LogicApplier, data jsonlogic.DataType, params []jsonlogic.RuleType) (jsonlogic.DataType, error) {
if len(params) != 2 {
return nil, errors.New("only support 2 params")
}
var (
p0, p1 interface{}
err error
)
// apply jsonlogic to each parameters recursively
if p0, err = applier.Apply(params[0], data); err != nil {
return nil, err
}
if p1, err = applier.Apply(params[1], data); err != nil {
return nil, err
}
p0f, ok0 := p0.(float64)
p1f, ok1 := p1.(float64)
if !ok0 || !ok1 {
return nil, errors.New("params should be numbers")
}
// recursive GCD function
var gcdFunc func(a int, b int) int
gcdFunc = func(a int, b int) int {
if b == 0 {
return a
}
return gcdFunc(b, a%b)
}
out := gcdFunc(int(p0f), int(p1f))
// to output a number, always use float64
return float64(out), nil
}
// Create an instance of `jsonlogic`, and register gcd operator
jl := jsonlogic.NewJSONLogic()
jl.AddOperation("gcd", gcd{})
// Use `gcd` as an operator to calculate: gcd(14+1, 25)
var rule interface{}
json.Unmarshal([]byte(`{"gcd": [{"+": [14, 1]}, 25]}`), &rule)
got, err := jl.Apply(rule, nil)
if err != nil {
// handle error
}
fmt.Println(got)
// Output: 5