options

This package provides a simple, flexible and convenient way of defining config options in Go.

When we want to specify config options for something, especially when there are a lot of optional options, the naive way of using struct or function with a long list of arguments doesn't work well in a lot of cases. Also, Go is a statically typed language, and doesn't provide a way to specify default arguments in function.

This package uses the power of Go reflections to make that task very simple. This is how you define and use a set of options with the help of this package:

//An option
type WhateverName struct{ Value string }

//An option
type WhateverNum struct{ Value int }

//Another option
type WhateverNum2 struct { Value float32 }

//WhateverSpec specifies the list of options
type WhateverSpec struct {
	Name WhateverName `js:"name"` //You may specify a tag here
	Num  WhateverNum  `js:"num"`
	Num2 WhateverNum2 `js:"num2"`
}

//Example convenience method for creating the master config
func WhateverOptions(opts ...Option) *OptionsProvider {
	return NewOptions(&WhateverSpec{}).Options(opts...)
}

//Example convenience method for retrieving the options
func GetWhateverOptions(o *OptionsProvider) *WhateverSpec {
	return o.Get().(*WhateverSpec)
}

func main() {
	//This is how you use the defined options
	opts := WhateverOptions(
		WhateverName{"n0t9r34t6czn0t9r34t1n49re4tw4y"},
		WhateverNum{99999},
	)

	println(GetWhateverOptions(opts).Name.Value) //Get the Name option value

	//You can export the options to a map
	m := opts.ExportToMapWithTag("js")
	_ = m["name"].(string) //Name exported to key "name", as specified by the tag
	
	opts.IsSet("Num") //returns true
	opts.IsSet("Num2") //returns false
	_, ok := m["num2"] //num2 doesn't appear in the result because it has not been set, returns false in ok
}

###Note:
Rob Pike once described a pattern for solving this problem (link). The client interface is good, it has rollbacks which is nice, but it's really really tedious to have to copy-paste dozens of lines of duplicated code for making the options, repeating the same logic for every options pack we create. It might be good for some, but for me it's unbearable. That's why this simple library is born.