In using django-tables2 app, how can I get an additional column, which does not correspond to a column in my database, but rather is computed from them in a certain way. As a simple example, suppose I have the model:
#models.py
class AddSub(models.Model)
num1 = models.DecimalField(max_digits=6, decimal_places=2)
num2 = models.DecimalField(max_digits=6, decimal_places=2)
op = models.CharField(max_length=3)
so my model is basically three columns, the first two are numbers the third is the operation to be performed, either 'SUB', 'ADD'. For example:
num1 |num2| op
1.01 5.67 'ADD'
87.3 23.4 'SUB'
.
.
.
Let's say I want a fourth column, computed from these three in the obvious way, namely it adds the two if the op is 'ADD' and subtracts if it is 'SUB'.
Finally, I have my table:
class CalcTable(tables.Table)
num1 = tables.Column(verbose_name='Operand 1')
num2 = tables.Column(verbose_name='Operand 2')
operation = tables.Column(verbose_name='Operation')
result = tables.Column(verbose_name='The Result')
How can I get django-tables2 to populate my results column? Is it through render? Perhaps something like
def render_result(self, value, record):
#add up
But my attempts at this have failed. In fact, even returning a constant with return 3.0, just left my fourth column blank.
If you add a new column and you populate the column using a render method, you need to add the empty_values attribute when defining the column.
result = tables.Column(verbose_name='The Result', empty_values=())