dictionary

A key→value composite for Composition-Oriented Programming — the sibling of array. A Dictionary wraps a map[interface{}]interface{} (arbitrary comparable keys, arbitrary values) behind a small Interface that follows the go-composites grammar:

• Never nil / Null-Object: every constructor and method returns a real object; Null() provides an inert variant and IsNull() distinguishes it.
• Result-based errors: fallible lookups return a Result — a payload on a hit, or a Result carrying Error.New("key not found") on a miss. No (value, ok), no panics, no bare nils.
• Composite returns: presence tests return a Boolean; Keys() and Values() return an Array.

Install

go get github.com/go-composites/dictionary@main

Usage

package main

import (
	"fmt"

	Dictionary "github.com/go-composites/dictionary/src"
	Result "github.com/go-composites/result/src"
)

func main() {
	d := Dictionary.New()
	d.Set("one", 1).Set("two", 2) // Set returns the Dictionary, so calls chain.

	fmt.Println(d.Len())                 // 2
	fmt.Println(d.Has("two").ToGoBool()) // true

	hit := d.Get("one")
	fmt.Println(hit.HasError(), hit.Payload()) // false 1

	miss := d.Get("nope")
	fmt.Println(miss.HasError(), miss.Error().Message()) // true key not found

	// Each short-circuits on the first Result whose HasError() is true.
	d.Each(func(key, value interface{}) Result.Interface {
		fmt.Printf("%v=%v\n", key, value)
		return Result.New()
	})

	// Keys() and Values() return an Array (order is unspecified — Go map order).
	_ = d.Keys()
	_ = d.Values()

	d.Delete("two")
}

API

Method	Returns	Notes
New(opts...)	Dictionary.Interface	empty by default; WithPairs seeds it
Null()	Dictionary.Interface	inert Null-Object; IsNull() is true
Set(key, value)	Dictionary.Interface	returns the receiver (chainable)
Get(key)	Result.Interface	payload on hit; error "key not found" on miss
Has(key)	Boolean.Interface	presence test
Delete(key)	Dictionary.Interface	no-op when absent; chainable
Len()	int	number of pairs
Keys()	Array.Interface	keys, unspecified order
Values()	Array.Interface	values, unspecified order
Each(fn)	Result.Interface	iterate; short-circuit on HasError()
IsNull()	bool	false for a real Dictionary

License

BSD-3-Clause — see LICENSE.