sand-co
v4.6.0
Published
generator async control flow goodness
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co
Generator based control flow goodness for nodejs and the browser, using promises, letting you write non-blocking code in a nice-ish way.
Why a Fork
This is the same pacakage as normal co yet it has domain support. Node has problems with domains and Promises, that is fixed in this version.
Co v4
[email protected]
has been released, which now relies on promises.
It is a stepping stone towards the async/await proposal.
The primary API change is how co()
is invoked.
Before, co
returned a "thunk", which you then called with a callback and optional arguments.
Now, co()
returns a promise.
co(function* () {
var result = yield Promise.resolve(true);
return result;
}).then(function (value) {
console.log(value);
}, function (err) {
console.error(err.stack);
});
If you want to convert a co
-generator-function into a regular function that returns a promise,
you now use co.wrap(fn*)
.
var fn = co.wrap(function* (val) {
return yield Promise.resolve(val);
});
fn(true).then(function (val) {
});
Platform Compatibility
co@4+
requires a Promise
implementation.
For versions of node < 0.11
and for many older browsers,
you should/must include your own Promise
polyfill.
When using node 0.10.x and lower or browsers without generator support, you must use gnode and/or regenerator.
When using node 0.11.x, you must use the --harmony-generators
flag or just --harmony
to get access to generators.
Node v4+ is supported out of the box, you can use co
without flags or polyfills.
Installation
$ npm install co
Associated libraries
Any library that returns promises work well with co
.
- mz - wrap all of node's code libraries as promises.
View the wiki for more libraries.
Examples
var co = require('co');
co(function *(){
// yield any promise
var result = yield Promise.resolve(true);
}).catch(onerror);
co(function *(){
// resolve multiple promises in parallel
var a = Promise.resolve(1);
var b = Promise.resolve(2);
var c = Promise.resolve(3);
var res = yield [a, b, c];
console.log(res);
// => [1, 2, 3]
}).catch(onerror);
// errors can be try/catched
co(function *(){
try {
yield Promise.reject(new Error('boom'));
} catch (err) {
console.error(err.message); // "boom"
}
}).catch(onerror);
function onerror(err) {
// log any uncaught errors
// co will not throw any errors you do not handle!!!
// HANDLE ALL YOUR ERRORS!!!
console.error(err.stack);
}
Yieldables
The yieldable
objects currently supported are:
- promises
- thunks (functions)
- array (parallel execution)
- objects (parallel execution)
- generators (delegation)
- generator functions (delegation)
Nested yieldable
objects are supported, meaning you can nest
promises within objects within arrays, and so on!
Promises
Thunks
Thunks are functions that only have a single argument, a callback.
Thunk support only remains for backwards compatibility and may
be removed in future versions of co
.
Arrays
yield
ing an array will resolve all the yieldables
in parallel.
co(function* () {
var res = yield [
Promise.resolve(1),
Promise.resolve(2),
Promise.resolve(3),
];
console.log(res); // => [1, 2, 3]
}).catch(onerror);
Objects
Just like arrays, objects resolve all yieldable
s in parallel.
co(function* () {
var res = yield {
1: Promise.resolve(1),
2: Promise.resolve(2),
};
console.log(res); // => { 1: 1, 2: 2 }
}).catch(onerror);
Generators and Generator Functions
Any generator or generator function you can pass into co
can be yielded as well. This should generally be avoided
as we should be moving towards spec-compliant Promise
s instead.
API
co(fn*).then( val => )
Returns a promise that resolves a generator, generator function, or any function that returns a generator.
co(function* () {
return yield Promise.resolve(true);
}).then(function (val) {
console.log(val);
}, function (err) {
console.error(err.stack);
});
var fn = co.wrap(fn*)
Convert a generator into a regular function that returns a Promise
.
var fn = co.wrap(function* (val) {
return yield Promise.resolve(val);
});
fn(true).then(function (val) {
});
License
MIT