Learned something new from Ted today
Read original post by Ted here
Flex is an event driven programming model and everything happens due to an event. Looking at the MXML code can confuse most of the developers unless they haven’t looked at the internal class of flex components. If we were to compare Flex, HTML and FLASH in terms of component instantiation.
- HTML instantiates top to bottom
- Flash executes across frames starting at Frame zero.
- Flex on the other had is a bit different.
When I started learning Flex, I struggled with understanding event flow and instantiation in MXML. I was puzzled because I really didn’t understand how event chain started and what happened inside a component to make it finally render on screen. Initially I used to run into numerous runtime null point exception since i used to think i could access a property of an object thinking it would have been created.
Anyhow the key is understanding the event basics and seeing the initialization and event flow, Lets look at a sample application that i have written to explain this. The structure of the application cann be understood by the following diagram.
With this Demo app there is no visual clue that you will get as an output to understand the event flow and instantiation step. its the TRACE statements that are important to explain how the event flow and instantiation happens. Below is the code for the same.
