A simple example of a promise with bluebird and coffeescript works in half the time
So, I'm basically trying to write simple code using promises and I'm having trouble understanding why this particular code works every time.
Promise = require('bluebird')
mkdirp = Promise.promisify(require('mkdirp'))
rm = Promise.promisify(require('rimraf'))
console.log "Preparing build directory"
rm('build')
.then(mkdirp('build'))
This will complete the first run successfully, but the second will fail, etc.
Here are the steps:
┌[adam@bigboi] [/dev/pts/5] [master ⚡]
└[~/Projects/bummyjab]> time coffee index.coffee ~/Dropbox/Articles/*.md
Preparing build directory
coffee index.coffee ~/Dropbox/Articles/*.md 0.25s user 0.02s system 100% cpu 0.267 total
┌[adam@bigboi] [/dev/pts/5] [master ⚡]
└[~/Projects/bummyjab]> stat build
File: ‘build’
Size: 4096 Blocks: 8 IO Block: 4096 directory
Device: 804h/2052d Inode: 17172395 Links: 2
Access: (0775/drwxrwxr-x) Uid: ( 1000/ adam) Gid: ( 1000/ adam)
Access: 2015-06-25 22:07:49.061331341 -0400
Modify: 2015-06-25 22:07:49.061331341 -0400
Change: 2015-06-25 22:07:49.061331341 -0400
Birth: -
┌[adam@bigboi] [/dev/pts/5] [master ⚡]
└[~/Projects/bummyjab]> time coffee index.coffee ~/Dropbox/Articles/*.md
Preparing build directory
Unhandled rejection Error: EEXIST: file already exists, mkdir '/home/adam/Projects/bummyjab/build'
at Error (native)
coffee index.coffee ~/Dropbox/Articles/*.md 0.20s user 0.03s system 100% cpu 0.235 total
Unfortunately my Google skills for this have no reason why this is happening.
thank
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If you are trying to control the order so that it mkdirp('build')
only executes after completion rm('build')
, you need to pass a function reference to the .then()
following:
rm('build').then(function () {
return mkdirp('build');
});
Or you can use .bind()
:
rm('build').then(mkdirp.bind(null, 'build'));
What you were doing was to execute immediately mkdirp()
and pass that return value to .then()
, which doesn't wait to be fulfilled until the promise is resolved.
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