Blogger2: No mention of 'dependent: :delete_all', which seems necessary

[jinjagit]

EDIT [Just realized these problems may be due to me using Rails 5.2.0, not 4.0.0 as in the tutorial. if so, sorry :-)]

After creating comments and tags functionality, the delete article function breaks. A solution is to edit the article.rb file to include;
dependent: :delete_all
in the lines:

has_many :comments, dependent: :delete_all
has_many :taggings, dependent: :delete_all

I discovered this by comparing my work to other students', since I found no explanation of this in the tutorial itself. I hate blindly copying stuff I have not understood, and since this is likely to be the first Rails app development done by us students, this seems to be a flaw (that might well confuse and demotivate).

Similarly, to be able to delete tags, tag.rb needs to include the line:

has_many :taggings, dependent: :destroy

Again, this is not explained in the tutorial, nor the related concept(s). I did find a StackOverflow post that touched on this, however (after laboriously checking all my files against another student's, and then googling the 'dependent: :destroy' term!).

Is this best practice? How do these terms solve the issues that not having them creates (Foreign key errors)? It seems unlikely that most beginner students will find these solutions, never mind understand them.