Creating nested Hash in Ruby - ruby

Question

I'm trying to write data from a forum into a JSON file. The hierarchy in the JSON file is supposed to look something this:
thread_id
post_id
...some_items...
Or more specifically:
{
"0101": {
"title": "Hi everybody",
"1001": {...},
"1002": {...}
},
}
The relevant part in my function looks like this:
return {
thread_id.to_i => {
:title => title,
post_id.to_i => {...}
}
}
The result is that each post becomes the child of a new parent thread_id:
{
"0101":{
"title":"Hi everybody",
"1001":{...}
},
"0101":{
"1002":{...}
}
}
What am I doing wrong?

Answer 1

First of all, the JSON schema you're trying to achieve is not quite right in my opinion. See what you think of this:
{
"threads": [
{
"id": 100,
"title": "Lorem ipsum dolor sit amet",
...
"posts": [
{
"id": 1000,
"body": "Lorem ipsum dolor sit amet",
...
},
...
]
},
...
]
}
And the answer to your question depends on how your data is starting out, which we don't know, so I'll answer in terms of what I might expect the data structure to look like. (Note: don't use the constant Thread; it is already a Ruby class used for something totally unrelated.)
class ForumThread
def self.serialize(threads)
{ threads: threads.map(&:serialize) }
end
def serialize
attrs_to_serialize.inject({}) do |hash, attr|
hash[attr] = send(attr)
hash
end
end
def serialized_posts
posts.map &:serialize
end
def attrs_to_serialize
[:id, :title, ..., :serialized_posts]
end
end
class ForumPost
def serialize
attrs_to_serialize.inject({}) do |hash, attr|
hash[attr] = send(attr)
hash
end
end
def attrs_to_serialize
# same sort of thing as above
# ...
end
end
# Given the `threads` variable below holds an array or array-like
# object of ForumThread instances you could do this:
JSON.generate ForumThread.serialize(threads) # => { "threads": [...] }