The truth is that closed systems still win. Open systems, practically speaking, are basically good for making others lose. The art of business in the 21st century is figuring out how to open up your suppliers’ and competitors’ business while keeping yours tightly sealed. And in that endeavor Google has proven highly successful.

Since the primary use for this knowledge is managing the initialization portion of the component life cycle, I’ve highlighted the lines where your component may extend the behavior of UIComponent to perform its own operations.

The addChild() code bounces around through a lot of the Container class hierarchy, so I’ve included the class name with the method calls inside the parent’s instance so that you know where in the class hierarchy things get handled.

For simplicity, I skip showing the parameters to method calls and I don’t expand some operations (depicted by italicized text).

1. Container.addChild()
   1. calls Container.addChildAt()
      1. removes child’s previous parent, if present
      2. calls Container.addingChild()
         1. calls UIComponent.addingChild()
            1. calls child.parentChanged()
            2. performs style setup on child
            3. calls child.stylesInitialized()
         2. invalidates size and display list of parent
      3. calls UIComponent.$addChildAt()
         1. calls Sprite.addChild()
      4. calls Container.childAdded()
         1. parent dispatches “childrenChanged”
         2. parent dispatches “childAdd”
         3. calls child.dispatchEvent()
            1. child dispatches “add”
         4. calls UIComponent.childAdded()
            1. calls child.initialize()
               1. dispatches “preinitialize”
               2. calls child.createChildren()
               3. calls child.childrenCreated()
                  1. invalidates properties, size, and display list of child
               4. calls child.initializeAccessibility()
               5. calls child.initializationComplete()
                  1. sets processedDescriptors = true
                     1. dispatches “initialize”

There you have it: the order of operations when you invoke Container.addChild(). I hope this proves useful.

UPDATE: With the NDA lifted, Brad has generously released the source code for Molecules!

But, don’t mistake my belief in opinionated software to mean that I like the opinions of all opinionated software.

For example, Git is very opinionated software, but I don’t care much for it. Git was created to solve a specific problem, and consequently Git values strong support for non-linear development, distributed development, efficient handling of large projects, and fast merging of patches from email. As it turns out, my source code management needs have almost zero overlap with those features so Git is not a good fit for my development workflow. I recognize that those features are important to many projects, but they aren’t for me. Git can be exception at what it does because it doesn’t compromise to try to meet my needs, too.

And here’s the best part: I don’t have to use Git. If it’s opinions don’t mesh with mine, we can agree to disagree and I can choose a tool better suited for my needs. Some commentators seem to miss this point. Opinionated software doesn’t preach “one true way”, it says “my way or the highway”—if my software doesn’t work for you, you’re free to find another solution that does work for you. (In the open source forums, this sentiment is echoed as “if you don’t like it, then fork it or build your own”.)