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author | Indrajith K L | 2022-12-03 17:00:20 +0530 |
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committer | Indrajith K L | 2022-12-03 17:00:20 +0530 |
commit | f5c4671bfbad96bf346bd7e9a21fc4317b4959df (patch) | |
tree | 2764fc62da58f2ba8da7ed341643fc359873142f /v_windows/v/old/vlib/eventbus/README.md | |
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Diffstat (limited to 'v_windows/v/old/vlib/eventbus/README.md')
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diff --git a/v_windows/v/old/vlib/eventbus/README.md b/v_windows/v/old/vlib/eventbus/README.md new file mode 100644 index 0000000..93047db --- /dev/null +++ b/v_windows/v/old/vlib/eventbus/README.md @@ -0,0 +1,122 @@ +# Event Bus + +A module to provide eventing capabilities using pub/sub. + +## API + +1. `new()` - create a new `EventBus` + +### Structs: + +**EventBus:** + +1. `publish(name string, sender voidptr, args voidptr)` - publish an event with provided + Params & name +2. `clear_all()` - clear all subscribers +3. `has_subscriber(name string)` - check if a subscriber to an event exists + +**Subscriber:** + +1. `subscribe(name string, handler EventHandlerFn)` - subscribe to an event +2. `subscribe_once(name string, handler EventHandlerFn)` - subscribe only once to an event +3. `subscribe_method(name string, handler EventHandlerFn, receiver voidptr)` - subscribe to + an event and also set the `receiver` as a parameter. + Since it's not yet possible to send methods as parameters, this is a workaround. +4. `is_subscribed(name string)` - check if we are subscribed to an event +5. `unsubscribe(name string)` - unsubscribe from an event + +**Event Handler Signature:** + +The function given to `subscribe`, `subscribe_method` and `subscribe_once` must match this: + +```v oksyntax +fn cb(receiver voidptr, args voidptr, sender voidptr) { +} + +// Since V can map structs to voidptr, this also works +struct ClickEvent { + x int + y int +} + +// Example case where publisher sends ClickEvent as args. +fn on_press(receiver voidptr, e &ClickEvent, sender voidptr) { + println(e.x) + // your code here... +} +``` + +## Usage + +For **usage across modules** +[check the example](https://github.com/vlang/v/tree/master/examples/eventbus). + +_Note: As a general rule, you will need to **subscribe before publishing**._ + +**main.v** + +```v oksyntax +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(receiver voidptr, e &Error, work &Work) { + println('error occured on ${work.hours}. Error: $e.message') +} +``` + +**work.v** + +```v oksyntax +module main + +import eventbus + +const eb = eventbus.new() + +struct Work { + hours int +} + +struct AnError { + message string +} + +fn do_work() { + work := Work{20} + // get a mutable Params instance & put some data into it + error := &AnError{'Error: no internet connection.'} + // publish the event + eb.publish('error', work, error) +} +``` + +### Notes: + +1. 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. +2. Each `EventBus` has a `Subscriber` 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. +3. 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 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. |