Promise

The Promise module in Lua. Simple, Fast and ES6 Promises full supported/compatibled.

About ES6 Promises see here: Promise in MDN

A chinese document at here: The Promise's World

Table of Contents

• Install & Usage
• Interface
• testcase or samples
• History

Install & Usage

Download the file Promise.lua and put it into lua search path or current directory, and load as module from lua.

Or use luarocks and require as module:

> luarocks install promise-es6

and, use Promise.new() or use Promise.xxx method to get promise object.

Promise = require('Promise')

p1 = Promise.new(function(resolve, reject)
  resolve('your immediate value, or result from remote query or asynchronous call')
end)

p2 = Promise.resolve('immediate value')

p1:andThen(function(value)
  print(value)
  return 'something'
end):andThen(..)   -- more

Interface

• For the Promsie class, call with '.'

Promise.new(executor)

promise = Promise.new(function(resolve, reject) .. end);

Promise.all(array)

promise = Promise.all(array)	-- a table as array

Promise.race(array)

promise = Promise.race(array)	-- a table as array

Promise.reject(reason)

promise = Promise.reject(reason);	-- reason is anything

Promise.resolve(value)

promise = Promise.resolve(value);
promise = Promise.resolve(thenable);
promise = Promise.resolve(promise);

• For promise instance, call with ':'

promise:andThen(onFulfilled, onRejected)

promise2 = promise:andThen(functoin(value) ... end);
promise2 = promise:andThen(nil, functoin(reson) ... end);

promise:catch(onRejected)

promise2 = promise:catch(functoin(reson) ... end)

testcase or samples

This is a base testcase:

---
--- from testcase/t_base_test.lua
---
Promise = require('Promise')

return10 = function() return 10 end
returnDoubled = function(a) print(a * 2) end
printX4 = function(a)
	print(a * 4)
	return Promise.resolve('ok')  -- or direct return 'ok'
end
printX3 = function(a) print(a * 3) end
unpackAndReject = function(result)
	local b, c, d = unpack(result)
	print(b, c, d)
	return Promise.reject('FIRE')
end

-- promise_A = Promise.resolve(A())
promise_r10 = Promise.new(function(resolve, reject)
	local ok, result = pcall(return10)
	return (ok and resolve or reject)(result)
end)
promise_B = promise_r10:andThen(returnDoubled)
promise_C = promise_r10:andThen(printX4)
promise_D = promise_r10:andThen(printX3)

promises = {promise_B, promise_C, promise_D}
Promise.all(promises)
	:andThen(unpackAndReject)
	:catch(function(reson)
		print(reson)
	end)

History

• 2017.04.26 release v1.2, fix some bugs

	- fix bug: value deliver on promise chain, about issue-#3, thanks for @stakira
	- ignore rewrite promised value

• 2015.10.29 release v1.1, fix some bugs

 	- update testcases
 	- update: add .catch() for promised string
 	- update: protect call in .new method
 	- fix bug: resolver values when multi call .then()
 	- fix bug: non standard .reject() implement
 	- fix bug: some error in .all() and .race() methods

• 2015.08.10 release v1.0.1, full testcases, minor fix and publish on github

• 2015.03 release v1.0.0