Adding today's date into attribute table using QGIS Processing modeler?

Question

I am looking for a way to use the Processing modeler to add a date field to an output dataset in QGIS 2.6.1

I have tried using the field calculator algorithm without success. (Also the advanced python field calculator without success).

I have a vector layer and I add a field calculator algorithm and set the field type to Date, field length to 30, precision to 0, create new field and set the formula to $now I have also tried datetime.date.today()

The error I get is;

Prepare algorithm 0: Field calculator Running Field calculator [1/1] Parameters: INPUT_LAYER =C:/Users/lee/Desktop/TEMP/test.shp, FIELD_NAME =loadDate, FIELD_TYPE =3, FIELD_LENGTH =30, FIELD_PRECISION =0, NEW_FIELD =True, FORMULA =$now Failed Error executing algorithm 0 underlying C/C++ object has been deleted

(I am looking to automate the process of adding a 'loadDate' field to features so that users know when a feature was loaded into a postgis table. I want to repeat it over a number of layers, and do it on a regular basis hence the use of the modeler).

Answer 1

I have found the answer I need by using the advanced python field calculator.

I set the following parameters;

Field type:String

Field length: 10

Global Expression: import time

Formula: value = time.strftime("%Y-%m-%d")

This gave me a new field with today's date added at the end.

Answer 2

I think there's a bug somewhere as I also use QGIS 2.6.1. I tried a few times to do this in Model Builder using the $now command and received an empty column. I then exported the model as a python script, made some edits and ran it. Again I received NULL values. Then suddenly, when I ran the model again, it works... I cannot explain how but it's weird. I've included a screenshot of the options I used in the Model Builder:

Here's the script I used which you can add via Processing Toolbox > Scripts > Tools > Create new script:

##Date=name
##Layer=vector
##Result=output vector
processing.runalg("qgis:fieldcalculator", Layer, "loadDate", 3, 10, 0, True, '$now', Result)

Hope this helps somehow!