Self-Managing, configurable structs for Edinburgh's Golang Developer Meetup, July '18

incrementing_structs.go

package SelfIncrementingStruct

import "SelfManagingStructs/TomTypes"


var (
	runAlready = false
	CollectionSize = 5
	usageLimit = 3
	SMSCollection = make(chan TomTypes.SelfManagingStruct, CollectionSize)
)

// Initialise a new struct properly, with the StructIncrementer as its "manager"
func constructNewSMStruct() TomTypes.SelfManagingStruct {
	return TomTypes.SelfManagingStruct{
		Manager: 		StructIncrementer,
		Counter:		0,
		Limit:			usageLimit,
	}
}

// The function that'll increment values in our struct.
func StructIncrementer (sms TomTypes.SelfManagingStruct) {    // NOTE: this is a TomTypes.ReturnManager

	sms.Counter++

	// Refresh our structs if they hit a usage limit!
	if sms.Counter == sms.Limit {
		sms = constructNewSMStruct()
	}

	// Pop it back on the stack.
	SMSCollection <- sms
}

// Get a self-incrementing struct from our collection of structs.
func GetSMStruct() TomTypes.SelfManagingStruct {

	// If we haven't ever populated the channel before, do that.
	if !runAlready {
		var c int
		for c = 0; c < CollectionSize; c++ {
			SMSCollection <- constructNewSMStruct()
		}
		runAlready = true
	}

	// Just take something from the channel!
	return <-SMSCollection

}

main.go

package main

import (
	"SelfManagingStructs/SelfIncrementingStruct"
	"SelfManagingStructs/TomTypes"
	"fmt"
	"time"
)

func main() {
	// Loop through our struct and print the counter value. We'll see them reset as they reach a usage limit.
	var incStruct TomTypes.SelfManagingStruct
	for {
		incStruct = SelfIncrementingStruct.GetSMStruct()
		fmt.Println(incStruct.Counter)
		incStruct.ManageSelf()
		time.Sleep(500 * time.Millisecond)
	}
}

types.go

package TomTypes

type ReturnManager func(SelfManagingStruct)


type SelfManagingStruct struct {
	Manager ReturnManager
	Counter int
	Limit int
}

func (sms SelfManagingStruct) ManageSelf() {
	sms.Manager(sms)
}