Thursday, May 15, 2014

appl.curTransactionId()

hi,

Ever since I started working with Ax, there has been a curTransactionId() method in the xApplication object. Never really used it ... until today.

Here's a summary of how and why I used it.

My goal was to link data from a bunch of actions in X++ code together. In my case, there was practically no option to pass parameters through and forth between all the classed involved. Imagine the calls tack of the sales order invoice posting for example where I needed to glue runtime data from the tax classes to data in classes about 30 levels higher in the call stack.

The solution I came up with was the combination of the appl.globalCache() and the app.getTransactionId(). Basically I add the data I want to use elsewhere to the globalCache (which is session specific, so whatever you put in it is only available within the same Ax session), and retrieve that data again wherever I want to.

For example:
- I'm adding a value to the globalCache using a string ('myPrefix' + appl.curTransactionId(true)) as the owner
- I'm retrieving it anywhere in code (within the same transaction) by getting it back from the globalCache using the same way ('myPrefix' + appl.curTransactionId()) and I'm sure

So what does this curTransactionId() actually do?
A call to appl.curTransactionId() returns the ID of the current transaction . Easy as that.
Owkay ... but what is 'the current transaction'?
Well, if the conditions below are met, appl.curTransactionId() will return a unique non-zero value:
- the call must be in a ttsBegin/ttsCommit block
- there must be an insert in the tts block on a table that has the CreatedTransactionId set to 'yes'
- OR there must be an update in the tts block on a table that has the ModifiedTransactionId set to 'yes'
So, in short: it is the unique ID of the actual transaction your code is running in.
You can nest as many tts blocks as you wish, they will all share the same transaction ID, which is only logical.

If there is no tts block, or no insert/update, or no table with CreatedTransactionId or ModifiedTransactionId set to 'yes', appl.curTransactionId() will just return '0' (zero).

If you do want to generate a transaction ID yourself, you can set the optional ForceTakeNumber parameter to 'true', like this: appl.curTransactionId(true).
This will forcibly generate a transaction ID, regardless of the conditions mentioned above.
It gets even better: if you call appl.curTransactionId(true) while the conditions mentioned above are met, it will return you the same ID it would have returned without the ForceTakeNumber parameter set to true. Or, in other words: it does not generate a new ID if there is already an existing one.

If you forcibly generate a transaction ID before entering a tts block, the transaction ID in the tts block will still be the same (even if the conditions regarding table with CreatedTransactionId/ModifiedTransationID are met).
If you forcibly generate a transaction ID inside a tts block that already has a transaction ID, the existing one will be kept.

It is only after the (most outer) ttsCommit that the transaction ID is reset to 0 (zero).
Calling appl.curTransactionId(true) again then does result in a brand new ID.

It's not the intention to describe all scenario's possible, but I'd guess you get the idea by now.

Anyway, I've found the appl.curTransactionId() quite handy for linking stuff within the same transaction scope.

Enjoy!

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