status-lib/eventemitter.nim

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2021-09-08 18:05:39 +00:00
import # system libs
tables
import # deps
uuids
type
Args* = ref object of RootObj # ...args
Handler* = proc (args: Args) {.closure.} # callback function type
EventEmitter* = ref object
events: Table[string, Table[UUID, Handler]]
proc createEventEmitter*(): EventEmitter =
result.new
result.events = initTable[string, Table[UUID, Handler]]()
proc on(this: EventEmitter, name: string, handlerId: UUID, handler: Handler): void =
if this.events.hasKey(name):
this.events[name].add handlerId, handler
return
this.events[name] = [(handlerId, handler)].toTable
proc on*(this: EventEmitter, name: string, handler: Handler): void =
var uuid: UUID
this.on(name, uuid, handler)
proc once*(this:EventEmitter, name:string, handler:Handler): void =
var handlerId = genUUID()
this.on(name, handlerId) do(a: Args):
handler(a)
this.events[name].del handlerId
proc emit*(this:EventEmitter, name:string, args:Args): void =
if this.events.hasKey(name):
# collect the handlers before executing them
# because of 'once' proc, we also mutate
# this.events. This can cause unexpected behaviour
# while having an iterator on this.events
var handlers: seq[Handler] = @[]
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for (id, handler) in this.events[name].pairs:
handlers.add(handler)
for i in 0..len(handlers)-1:
handlers[i](args)
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when isMainModule:
block:
type ReadyArgs = ref object of Args
text: string
var evts = createEventEmitter()
evts.on("ready") do(a: Args):
var args = ReadyArgs(a)
echo args.text, ": from [1st] handler"
evts.once("ready") do(a: Args):
var args = ReadyArgs(a)
echo args.text, ": from [2nd] handler"
evts.emit("ready", ReadyArgs(text:"Hello, World"))
evts.emit("ready", ReadyArgs(text:"Hello, World"))