Test Your Knowledge
Quiz
Where do you specify data relationships?
How much effort does Rails put into enforcing relationships between models?
What does the
collect
method do?How can you check to see whether a related record exists?
Why would you want to go to the trouble of creating a nested resource?
When would you use a
before_filter
?What does
form_for
do when it is passed an array for its first argument?What two columns are needed in a join table?
Why would you want to index the columns of a join table?
Where do you tell Rails about new methods youâve added to the scaffolding?
Answers
Relationships are specified in models. The models on both sides of any given relationship must identify how they relate to the other model. For example, a
has_many
relationship in one model should be matched by abelongs_to
relationship in another model.Rails doesnât put any effort into enforcing relationships between models. If you have constraints to impose, you need to create code that checks and enforces them.
The
collect
method iterates over a collection and gathers the results from a block. Itâs an easy way to turn a list of data into aselect
list, for instance.You could check for a related record with
find
, but in most validation contexts itâs easier to use thevalidates_existence_of
plug-in. (If you want to check for a related valid record, then Railsâ built-invalidates_associated
will work.)Nested resources have some programming aesthetic appeal, but theyâre also useful for making relationships ...
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