README.md

Mutable

Introduction

Mutable package provides object changes tracking features and the way to set values to the struct dynamically by a destination field name (including nested structs).
This package needs Go version 1.9 or later

Usage

Installation

go get github.com/askretov/go-mutable

Embedding Mutable

package main

import "github.com/askretov/mutable"

type NestedStruct struct {
	mutable.Mutable
	FieldY string
	FieldZ []int64
}

type MyStruct struct {
	mutable.Mutable
	FieldA string
	FieldB int64        `mutable:"ignored"`
	FieldC NestedStruct `mutable:"deep"`
}

func main() {
    var m = &MyStruct{}
    // Mutable state init
    m.ResetMutableState(m)
}

Tracking changes

// Change values
m.FieldA = "green"
m.FieldC.FieldY = "stone"
// Analyze changes
fmt.Println(m.AnalyzeChanges())

Output:

{
        "FieldA": {
                "old_value": "",
                "new_value": "green"
        },
        "FieldC": {
                "nested_fields": {
                        "FieldY": {
                                "old_value": "",
                                "new_value": "stone"
                        }
                }
        }
}

Set values dynamically

// Set values
m.SetValue("FieldA", "white")
m.SetValue("FieldC/FieldZ", "[1,2,3]") // You can set typed value or JSON string as well
// Analyze changes
fmt.Println(m.AnalyzeChanges())

Output:

{
        "FieldA": {
                "old_value": "green",
                "new_value": "white"
        },
        "FieldC": {
                "nested_fields": {
                        "FieldZ": {
                                "old_value": null,
                                "new_value": [1, 2, 3]
                        }
                }
        }
}

Optional settings - Struct tags

Struct field's tag values should be set within mutable tag

• ignored - specifies ignoring of this field changes tracking
• deep - specifies the deep analyze of a field (only for struct kind fields). Instead of regular analysis of a field value itself, every field of nested struct will be analyzed for changes individually.

Example:

type MyStruct struct {
    mutable.Mutable
    FieldA string `mutable:"ignored"`
    FieldB AnotherStructType `mutable:"deep"`
}

Keep in mind

1. If you use a pointer to struct as field type and want to be able to use deep analysis, you have to embed Mutable for such nested field's struct as well.

   Example:

   type MyStruct struct {
       mutable.Mutable
       FieldA string
       FieldB *NestedStruct `mutable:"deep"`
   }
   
   type NestedStruct struct {
       mutable.Mutable // Mutable as well
       FieldY string
       FieldZ string
   }

2. If you pass a mutable object as an arg to a function, you have to pass it as a pointer to be able to use Mutable features.