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import noop from 'lodash/noop';
import rest from 'lodash/rest';
import reduce from './reduce';
/**
* Version of the compose function that is more natural to read. Each function
* consumes the return value of the previous function. It is the equivalent of
* {@link async.compose} with the arguments reversed.
*
* Each function is executed with the `this` binding of the composed function.
*
* @name seq
* @static
* @memberOf async
* @see async.compose
* @category Control Flow
* @param {...Function} functions - the asynchronous functions to compose
* @returns {Function} a function that composes the `functions` in order
* @example
*
* // Requires lodash (or underscore), express3 and dresende's orm2.
* // Part of an app, that fetches cats of the logged user.
* // This example uses `seq` function to avoid overnesting and error
* // handling clutter.
* app.get('/cats', function(request, response) {
* var User = request.models.User;
* async.seq(
* _.bind(User.get, User), // 'User.get' has signature (id, callback(err, data))
* function(user, fn) {
* user.getCats(fn); // 'getCats' has signature (callback(err, data))
* }
* )(req.session.user_id, function (err, cats) {
* if (err) {
* console.error(err);
* response.json({ status: 'error', message: err.message });
* } else {
* response.json({ status: 'ok', message: 'Cats found', data: cats });
* }
* });
* });
*/
export default rest(function seq(functions) {
return rest(function(args) {
var that = this;
var cb = args[args.length - 1];
if (typeof cb == 'function') {
args.pop();
} else {
cb = noop;
}
reduce(functions, args, function(newargs, fn, cb) {
fn.apply(that, newargs.concat([rest(function(err, nextargs) {
cb(err, nextargs);
})]));
},
function(err, results) {
cb.apply(that, [err].concat(results));
});
});
})
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