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Improve Promise documentation.

v0.7.4-release
Ryan 16 years ago
parent
commit
51addf19d8
  1. 36
      website/api.txt

36
website/api.txt

@ -141,7 +141,9 @@ Execute each of the listeners in order with the array +args+ as arguments.
==== +node.Promise+
Promises emit two special events +"success"+ and +"error"+.
+node.Promise+ inherits from +node.eventEmitter+. A promise emits one of two
events: +"success"+ or +"error"+. After emitting its event, it will not
emit anymore events.
[cols="1,2,10",options="header"]
|=========================================================
@ -150,10 +152,6 @@ Promises emit two special events +"success"+ and +"error"+.
| +"error"+ | (depends) |
|=========================================================
+node.Promise+ inherits from +node.eventEmitter+. A promise emits one of two
events: +"success"+ or +"error"+. After emitting its event, it will not
emit anymore events.
+promise.addCallback(listener)+ ::
Adds a listener for the +"success"+ event. Returns the same promise object.
@ -383,36 +381,42 @@ File I/O is provided by simple wrappers around standard POSIX functions.
All POSIX wrappers have a similar form.
They return a promise (+node.Promise+). Example:
----------------------------------------
------------------------------------------------------------------------------
var promise = node.fs.unlink("/tmp/hello");
promise.addCallback(function () {
puts("successfully deleted /tmp/hello");
});
----------------------------------------
------------------------------------------------------------------------------
There is no guaranteed ordering to the POSIX wrappers. The
following is very much prone to error
----------------------------------------
------------------------------------------------------------------------------
node.fs.rename("/tmp/hello", "/tmp/world");
node.fs.stat("/tmp/world").addCallback(function (stats) {
puts("stats: " + JSON.stringify(stats));
});
----------------------------------------
------------------------------------------------------------------------------
It could be that +stat()+ is executed before the +rename()+.
The correct way to do this is to chain the promises.
----------------------------------------
node.fs.rename("/tmp/hello", "/tmp/world")
.addCallback(function () {
node.fs.stat("/tmp/world")
.addCallback(function (stats) {
------------------------------------------------------------------------------
node.fs.rename("/tmp/hello", "/tmp/world").addCallback(function () {
node.fs.stat("/tmp/world").addCallback(function (stats) {
puts("stats: " + JSON.stringify(stats));
});
});
----------------------------------------
});
------------------------------------------------------------------------------
Or use the +promise.block()+ functionality:
------------------------------------------------------------------------------
node.fs.rename("/tmp/hello", "/tmp/world").block();
node.fs.stat("/tmp/world").addCallback(function (stats) {
puts("stats: " + JSON.stringify(stats));
});
------------------------------------------------------------------------------
+node.fs.rename(path1, path2)+ ::
See rename(2).

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