3.5 KiB
3.5 KiB
Event Bus
A module to provide eventing capabilities using pub/sub.
API
new()
- create a newEventBus
Structs:
EventBus:
publish(string, voidptr, Params)
- publish an event with provided Params & nameclear_all()
- clear all subscribershas_subscriber(string)
- check if a subscriber to an event exists
Subscriber:
subscribe(string, fn(voidptr, Params))
- subscribe to an eventsubscribe_once(string, fn(voidptr, Params))
- subscribe only once to an eventis_subscribed(string)
- check if we are subscribed to an eventunsubscribe(string)
- unsubscribe from an event
Event Handler Signature:
The function given to subscribe
and subscribe_once
must match this:
fn(voidptr, Params){
}
// Example
fn onPress(sender voidptr, p Params){
//your code here...
}
Usage
For usage across modules check the example.
Note: As a general rule, you will need to subscribe before publishing.
main.v
module main
import eventbus
// initialize it globally
const (
eb = eventbus.new()
)
fn main(){
// get a mutable reference to the subscriber
mut sub := eb.subscriber
// subscribe to the 'error' event
sub.subscribe("error", on_error)
// start the work
do_work()
}
// the event handler
fn on_error(sender voidptr, p eventbus.Params) {
//cast the sender to the real type
//you can also make this mutable if required.
work := *(*Work(sender)) //a little verbose but works
error := p.get_string("error")
println('error occured on ${work.hours}. Error: ${error}')
}
work.v
module main
import (
eventbus
)
struct Work{
hours int
}
fn do_work(){
work := Work{20}
// get a mutable Params instance & put some data into it
mut params := eventbus.Params{}
params.put_string("error", "Error: no internet connection.")
// publish the event
eb.publish("error", work, params)
}
How to use Params
:
mut params := eventbus.Params{}
params.put_string("string", "some_string")
params.put_int("int", 20)
params.put_bool("bool", true)
// add maps and arrays of any type like this
arr := [1,2,3]
params.put_array("array", arr)
mp := {"hello": "world"}
params.put_map("map", mp)
//get and use the params like this
assert params.get_string("string") == "some_string"
assert params.get_int("int") == 20
assert params.get_bool("bool") == true
g_arr := params.get_array("array", 0)
assert g_arr[0] == 1
g_m := params.get_map("map", "")
assert g_m["hello"] == "world"
Caution when putting arrays:
Currently putting arrays and maps directly as parameters in put_array
doesn't work, so make a variable first and use that.
Notes:
- Each
EventBus
instance has it's own registry (i.e. there is no global event registry so you can't just subscribe to an event wherever you are. - Each
EventBus
has aSubscriber
instance which will need to be either exposed or you can make small public helper functions specific to your module like (onPress
,onError
) and etc. - The
eventbus
module has some helpers to ease getting/setting of Params (since V doesn't support empty interfaces yet or reflection) so use them (see usage above).
The rationale behind separating Subscriber & Publisher:
This is mainly for security because the if publisher & subscriber are both passed around, a client can easily publish events acting as the server. So a client should only be able to use the Subscriber methods.