Bob's Blog

This was asked today on the Transfer mailing list:

I thought that my response was worthy of a blog post, so here goes.

Firstly, there is a getMemento() method that gets generated for all Transfer objects, which returns this type of struct. The problem is that it is undocumented and therefore unsupported. This method could change and/or disappear at any time, so it's not really safe to use. I use it occasionally while developing and debugging, but I'd never use it in real application code.

Transfer does provide access to its own internal metadata via getTransferMetaData(), which you can call on the base Transfer class. This metadata is chock full of useful information which I've made use of in a number of situations. I too needed to generate a simple struct that contained property name/value pairs, so I wrote a method which I've placed in my AbstractTransferDecorator which serves that purpose. Here's the code, broken up into sections to allow for some explanation:

So first I grab the Transfer metadata for this class. getClassName() is a generated method that exists for every Transfer object. I know I want to populate keys in my structure for all of the properties of my Transfer object, so I grab the PropertyIterator from the metadata. My primary key, identified as an id in transfer.xml will not be included in the PropertyIterator, so I need to ask for that separately.

I use the PrimaryKey from the metadata to determine the name of id, which I then use to call the associated get() method. I then add this name/value pair to the struct. Because I want this routine to be able to add information to an existing struct, I may not always want it to overwrite any existing keys in the struct, which is the reason that I'm allowing the caller to pass in an argument for overwrite. The StructInsert function allows you to specify overwrite as either true or false, so this allows me to implement this logic. Unfortunately, if you specify overwrite as false and the key actually exists an exception is thrown, which is the reason that I've wrapped my call to StructInsert in a cftry. There's probably a more elegant way of doing this, but I haven't taken the time to find one... yet.

I loop through the PropertyIterator, doing the same thing as above - getting the value with a getter and then adding it to the struct.

At this point I have my id and all properties copied into my struct. An issue I encoutered is that I have some custom methods in my decorator and they are not exposed as properties to Transfer. For example, you might define a getAge() method which calculates a person's age based on their date of birth and the current date. if you want that copied to the struct as well, it won't happen if you rely solely on Transfer metadata. To allow for this I define a variable in the Configure() method of my object's decorator called ExtraProperties, and I populate it with an array of property names. These names correspond with the custom getters that I created, and for which I want values copied into my struct.

And that's the end of the method.

For anyone interested in cutting and pasting, here's the whole function, with a few extra comments: