I’ve just committed the latest changes to SproutCore to support property chaining.  This is an important change the SC API that could impact your code, though most likely only for the better.

The Old World

set() has always returned the value that you set of an object.  Since it was intended to replace the “=” in JS, this makes sense.  Just like you could do:

foo.bar = foo2.bar = c

You could do:

foo.set('bar', foo2.set('bar', c)) ;

The problem, of course, is that this model of setting values is not terribly useful.  In my informal survey, in fact, it appeared that almost no one actually uses it.

The New World

Enter the new world of chainable commands.  jQuery has gained a large following thanks mostly to its nifty chainability syntax.  Most methods return the object you just called a method on so you can chain commands like this:

$('.foo').show().css('color','red');

And all elements with CSS class ‘foo’ will be made visible and their color set to red.  Nice.  

This is a very useful way of writing JavaScript and we’re all about efficiency so SproutCore is moving towards a general pattern whereby methods that otherwise would return void, will now return this so you can do chaining.  The first place I’m implementing this pattern is in set().  With the latest SproutCore, instead of returning the value, set() now returns the receiver object.  Other property-related methods such as beginPropertyChanges() and endPropertyChanges() also do this.  This makes it easy to write compact code like this:


contact.beginPropertyChanges()
  .set('firstName','Charles')
  .set('lastName', 'Jolley')
  .endPropertyChanges();


Very compact!

What Do You Need To Change

Unless you’ve relied on the return value of set() in the past, you don’t need to do anything!  Just start enjoying the new compact syntax.  You don’t have to use it, but now it’s there for you.  If you have relied on the return value of set(), then you need to modify your code to use a separate get() on the method after you set it first.

The new SproutCore changes are available from git and SVN today and will be in the 1.0 release of the SproutCore gem.

Tags: New Features //