Currently, overwrite requires Go version 1.13 or greater.

This repository contains a library that enable caller to setup two structs of the same type and copy only tagged values between then.

Possible use cases are:

• Dynamically set up a struct based on input files
• Overloading secret configuration in environments where secrets are stored outside repo, escpecially useful for docker and kubernetes environments.

import "github.com/phelian/overwrite"

type Config struct {
    Username string
    Password string `overwrite:"true"`
    Driver string `overwrite:"true,omitempty"`
}

func main() {
    cfg := &Config{
        Username: "bernie",
        Driver: "postgres",
    }

    secretCfg := Config {
        Password: "feelthe",
    }

    if err := overwrite.Do(cfg, secretCfg); err != nil {
        panic(err)
    }
}

The result will be that cfg be a pointer to a Config struct with contents

{
    Username: "bernie",
    Password: "feelthe",
    Driver: "postgres",
}

Do copies tagged fields of arguments into

dst needs to be a pointer to same type of struct that src is src needs to be passed as value and not a pointer

Do traverses the value src recursively. If an encountered field is tagged to overwrite it tries to copy the value of that field into the dst counterpart field.

`overwrite:"<true/false>[,omitempty]"`

Possible arguments for tag are boolean "true" or "false" with possibility to add ",omitempty" in the end.

There types can be overwritten, others will be silently ignored

• int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64
• string
• boolean
• float32, float64 Also
• arrays, slices, maps and structs containing compatable types

• Throw error on unsupported types with tags
• Add tag to allow for configuration to only overwrite is destination struct is empty