javascript - Is there a problem with vue :class?

Question

The code is as shown in the figure. I control the true or false of the selectLessonCtrl data element through the click event, but the select class is not added. Is it a problem with $index?

Answer 1

Wrong writing, please read the document carefully
Ternary judgment: :class="[xxx ? 'xxx' : 'xxx']"
Is there any: :class="{ active: isActive, 'text-danger': hasError }"
There are other things, it’s best to read the documentation carefully, https://cn.vuejs.org/v2/guide...

Answer 2

Then selectLessonCtrl returns true?