Summary

This library has two major goals:

1. Provide data types to be used during incoming and outgoing data mapping for optional values
2. Provide safe and sufficient mapping functions to work with optional values

TL&DR;

Simple declare optional. data type in your struct

type Configuration struct {
    Hostname optional.String `json:"hostname"`
    Port     optional.Int    `json:"port"`
}

func main() {
    bts, err := ioutil.ReadFile("config.json")
    if err != nil {
        panic(err)
    }
    var c Configuration
    if err := json.Unmarshal(bts, &v); err != nil {
        panic(err)
    }

    host := c.Hostname.OrElse("localhost")
    port := c.Port.OrElse(3306)
}

Features

Supported mapping:

• JSON
• SQL
• YAML compatible with https://github.com/go-yaml/yaml
• TOML decoding only, compatible with https://github.com/BurntSushi/toml

Data types, all of them are immutable:

• optional.Bool - for booleans
• optional.Int - for integers
• optional.String - for strings
• optional.Float64 - for floats
• optional.Time - for time.Time, mapping using optional.TimeUnixSeconds
• optional.Duration - for time.Duration, mapping using optional.DurationSeconds, optional.DurationMillis or optional.DurationMinutes

Common methods for all data types:

• Get - returns value from optional, but panics if optional is empty
• OrElse(els) - returns value from optional or provided els value if optional is empty
• IsPresent - returns true if optional contains vaue, false otherwise
• IfPresent(func) - invokes provided func over value from optional if optional not empty
• Filter(predicate) - applies predicate over optional value
• MapToString(func), MapToInt(func), MapToFloat(func), MapToBool(func) - maps optional value to other type using func