Bell

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Bell is the simplest event system written in Go (Golang) which is based on the execution of handlers independent of the main channel.

• Written in pure go. Has no third-party libraries.
• Support for custom event data.
• Internally, it launches each handler in a separate goroutine and passes messages to them through channels, the handlers are executed independently of the main thread.
• Support for adding multiple handlers to an event.
• Complete unit testing.

Bull does not contain logic for automatic restarts in case of a crash and does not have a persistent execution state store.

To install Bell package, you need install Go with modules support and set Go workspace first.

1. Use the below Go command to install Bell:

go get -u github.com/nuttech/bell/v2

2. Import package in your code:

import "github.com/nuttech/bell/v2"

The handler function accepts the Message type as input

bell.Listen("event_name", func(message bell.Message) {
	// here you must write your handler code
})

bell.Message has interface{} type and can consist any data.

You can add more handlers one event:

bell.Listen("event_name", func(message bell.Message) { 
	// first handler
})
bell.Listen("event_name", func(message bell.Message) {
	// second handler
})

You can add a handler with multiple copies for parallel event processing.

bell.ListenN("event_name", func(msg bell.Message) { fmt.Println(msg) }, 42)

This code call event. Activating handlers, who subscribed on "event_name" event

bell.Ring("event_name", "some data")
bell.Ring("event_name", 1) // int
bell.Ring("event_name", false) // bool

If you passing struct type of data:

type userStruct struct {
	Name string
}
bell.Ring("event_name", userStruct{Name: "Jon"})

Then parsing the data in the handler may look like this:

bell.Listen("event_name", func(message bell.Message) {
	user := message.(userStruct)
	
	fmt.Printf("%#v\n", userStruct{Name: "Jon"}) // main.userStruct{Name:"Jon"}
})

To get a list of events to which handlers are subscribed, call the code:

bell.List()

You can check the existence of subscribers to an event like this:

bell.Has("event_name")

You can delete all listeners or listeners of only one event.

_ = bell.Remove()

_ = bell.Remove("event_name")

bell.Wait()

bell.Queue(42)

You can also use the bell package without using global state. To do this, you need to create a state storage object and use it.

events := bell.New()
events.Listen("event", func(message bell.Message) {})
_ = events.Ring("event", "Hello bell!")

See full example in example_test.go.