How can I apply a style rule to multiple categories? (2.14 and above)

Question

I think this used to be more straightforward in earlier QGIS versions, but with more powerful rule-based styling (great development) I am now a little confused as to how to apply a rule to multiple categories at once in the Style dialogue.

In the example below, I've styled my data using categories. I want to apply the $id = $atlasfeatureid rule to all categories because I'm working on an Atlas.

I'm guessing I'm missing something simple, but can't think what. It's not a problem to apply rule separately to a few categories but when working with 50+ it would be very time consuming.

Answer 1

You could add the main rule $id = $atlasfeatureid, without adding symbols:

Then select and drag all the other rules over it (over the label part). They should then become dependent of this first rule:

Answer 2

You could also use the following in the Python Console to change all expressions of each rule to $id = $atlasfeatureid:

layer = qgis.utils.iface.activeLayer()
renderer = layer.rendererV2()
for rule in renderer.rootRule().children():
    rule.setFilterExpression('$id = $atlasfeatureid')

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Edit:

The above code replaces all expressions entirely. However, if you want to add another expression to an existing one, you can use:

layer = qgis.utils.iface.activeLayer()
renderer = layer.rendererV2()
for rule in renderer.rootRule().children():
    rule.setFilterExpression('({}) AND $id = $atlasfeatureid'.format(rule.filterExpression()))