simplejson.go

package simplejson

import (
	"encoding/json"
	"errors"
	"log"
)

// returns the current implementation version
func Version() string {
	return "0.3"
}

type Json struct {
	data interface{}
}

// NewJson returns a pointer to a new `Json` object
// after unmarshaling `body` bytes
func NewJson(body []byte) (*Json, error) {
	j := new(Json)
	err := json.Unmarshal(body, &j.data)
	if err != nil {
		return nil, err
	}
	return j, nil
}

// Encode returns its marshaled data as `[]byte`
func (j *Json) Encode() ([]byte, error) {
	return json.Marshal(&j.data)
}

// Get returns a pointer to a new `Json` object 
// for `key` in its `map` representation
// 
// useful for chaining operations (to traverse a nested JSON):
//    js.Get("top_level").Get("dict").Get("value").Int()
func (j *Json) Get(key string) *Json {
	m, err := j.Map()
	if err == nil {
		if val, ok := m[key]; ok {
			return &Json{val}
		}
	}
	return &Json{nil}
}

// CheckGet returns a pointer to a new `Json` object and
// a `bool` identifying success or failure
//
// useful for chained operations when success is important:
//    if data, ok := js.Get("top_level").CheckGet("inner"); ok {
//        log.Println(data)
//    }
func (j *Json) CheckGet(key string) (*Json, bool) {
	m, err := j.Map()
	if err == nil {
		if val, ok := m[key]; ok {
			return &Json{val}, true
		}
	}
	return nil, false
}

// Map type asserts to `map`
func (j *Json) Map() (map[string]interface{}, error) {
	if m, ok := (j.data).(map[string]interface{}); ok {
		return m, nil
	}
	return nil, errors.New("type assertion to map[string]interface{} failed")
}

// Array type asserts to an `array`
func (j *Json) Array() ([]interface{}, error) {
	if a, ok := (j.data).([]interface{}); ok {
		return a, nil
	}
	return nil, errors.New("type assertion to []interface{} failed")
}

// Bool type asserts to `bool`
func (j *Json) Bool() (bool, error) {
	if s, ok := (j.data).(bool); ok {
		return s, nil
	}
	return false, errors.New("type assertion to bool failed")
}

// String type asserts to `string`
func (j *Json) String() (string, error) {
	if s, ok := (j.data).(string); ok {
		return s, nil
	}
	return "", errors.New("type assertion to string failed")
}

// Float64 type asserts to `float64`
func (j *Json) Float64() (float64, error) {
	if i, ok := (j.data).(float64); ok {
		return i, nil
	}
	return -1, errors.New("type assertion to float64 failed")
}

// Int type asserts to `float64` then converts to `int`
func (j *Json) Int() (int, error) {
	if f, ok := (j.data).(float64); ok {
		return int(f), nil
	}

	return -1, errors.New("type assertion to float64 failed")
}

// Int type asserts to `float64` then converts to `int64`
func (j *Json) Int64() (int64, error) {
	if f, ok := (j.data).(float64); ok {
		return int64(f), nil
	}

	return -1, errors.New("type assertion to float64 failed")
}

// Bytes type asserts to `[]byte`
func (j *Json) Bytes() ([]byte, error) {
	if s, ok := (j.data).(string); ok {
		return []byte(s), nil
	}
	return nil, errors.New("type assertion to []byte failed")
}

// MustString guarantees the return of a `string` (with optional default)
//
// useful when you explicitly want a `string` in a single value return context:
//     myFunc(js.Get("param1").MustString(), js.Get("optional_param").MustString("my_default"))
func (j *Json) MustString(args ...string) string {
	var def string

	switch len(args) {
	case 0:
		break
	case 1:
		def = args[0]
	default:
		log.Panicf("MustString() received too many arguments %d", len(args))
	}

	s, err := j.String()
	if err == nil {
		return s
	}

	return def
}

// MustInt guarantees the return of an `int` (with optional default)
//
// useful when you explicitly want an `int` in a single value return context:
//     myFunc(js.Get("param1").MustInt(), js.Get("optional_param").MustInt(5150))
func (j *Json) MustInt(args ...int) int {
	var def int

	switch len(args) {
	case 0:
		break
	case 1:
		def = args[0]
	default:
		log.Panicf("MustInt() received too many arguments %d", len(args))
	}

	i, err := j.Int()
	if err == nil {
		return i
	}

	return def
}

// MustFloat64 guarantees the return of a `float64` (with optional default)
//
// useful when you explicitly want a `float64` in a single value return context:
//     myFunc(js.Get("param1").MustFloat64(), js.Get("optional_param").MustFloat64(5.150))
func (j *Json) MustFloat64(args ...float64) float64 {
	var def float64

	switch len(args) {
	case 0:
		break
	case 1:
		def = args[0]
	default:
		log.Panicf("MustFloat64() received too many arguments %d", len(args))
	}

	i, err := j.Float64()
	if err == nil {
		return i
	}

	return def
}