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A tiny observer pattern library for Lua.
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talkback.lua

readme.md

Warning: This library is deprecated, and I no longer recommend using it. I recommend beholder or hump-signal if you need a good observer pattern library.

Talkback

Talkback is a small Lua library that lets you create "conversations". You can send messages from within a conversation, and you can create listeners that will do something (and optionally send back a response) when they receive a certain message. This is a powerful organizational tool that allows different parts of your code to interact with each other.

Examples

Player controls example

-- in main.lua
conversation = require 'lib.talkback'

-- in player.lua
conversation:listen('player jump', function()
  jump()
end)

-- in input-manager.lua
if input.pressed('x') then
  conversation:say('player jump')
end

High score display example

-- in score-manager.lua
conversation:listen('get high score', function(place)
  return scores[place]
end)

-- in hud.lua
topScore = conversation:say('get high score')
drawText(topScore)

Installation

To use the library, place talkback.lua in the root folder of your project or in a subfolder, and load it with require.

conversation = require 'talkback' -- if talkback.lua is in the root folder
conversation = require 'path.to.talkback' -- if it's in a subfolder

Usage

Listening for a message

listener = conversation:listen(message, f)

Creates a new listener. The listener will execute a function f when message is sent. message can be any Lua value.

  • Returns a handle to the listener. Store this in a variable if you want to remove the individual listener later.

Sending a message

response1, response2, ... = conversation:say(message, ...)

Sends message to every listener and returns each listener's response.

  • '...' are arguments that will be passed to each listener's function

Responses

If a listener's function returns values, conversation:say() will return those values if the listener's function is called. All of the responses will be returned in the order that each listener returns them and in the order that the listeners were added.

conversation:listen('lyrics', function() return 'some', 'body' end)
conversation:listen('lyrics', function() return 'once', 'told', 'me' end)
a, b, c, d, e = conversation:say('lyrics')
print(a) -- prints "some"
print(b) -- prints "body"
print(c) -- prints "once"
print(d) -- prints "told"
print(e) -- prints "me"

If you're not sure how many responses you'll get, and you want to collect all of them, you can collect the responses in a table:

lyrics = {conversation:say('lyrics')}
-- lyrics is now the table {'some', 'body', 'once', 'told', 'me'}

Removing listeners

listener:leave()

Removing all listeners for a certain message

conversation:ignore(message)

Removing all listeners

conversation:reset()

Groups

You can create sub-groups from the main conversation group. When you say or ignore messages from inside a group, only that group (and child groups) will listen. Groups can be nested infinitely, and Talkback itself is a group.

conversation = require 'talkback'

conversation:listen('greeting', function() print 'hello' end)
group = conversation:newGroup()
group:listen('greeting', function() print 'world' end)

conversation:say 'greeting' -- prints "hello" and "world"
group:say 'greeting' -- only prints "world"
group:ignore 'greeting'
conversation:say 'greeting' -- now only prints "hello"

Creating new groups

group = conversation:newGroup()
subGroup = group:newGroup()
-- etc.

Removing groups

group:leave()

Note: don't call group:leave() on the main Talkback group, as this will cause an error, since that group doesn't have a parent.

License

MIT License

Copyright (c) 2017 Andrew Minnich

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.