Fix NoMethodError in multithreading [issue-109]

[myxaluch]

In connection with #109

[mislav]

Could you instead add the mutex guard around the code in all method? That way we can have the synchronize call only in one place.

[myxaluch]

@mislav check all unless defined @all is in each methods names_index/unicode_index, and if we add mutex to allmethod only, we will not avoid problem, because, e.g. in first thread, in all, @all will be defined, but @names_index and @unicodes_index haven't yet, and second thread catch the NoMethodError.

[mislav]

That's a good point. In that case, can we simply call all from names_index/unicode_index instead of having the all unless defined @all expression?

Alternatively to this whole PR, do you think it would be worth it to populate all emoji in memory as soon as this library loads? Then there would be no multithreading issues, and threads wouldn't be slowed down by the fact they need to be synchronized around Emoji.find_by_* calls.

[myxaluch]

@mislav If we remove this check and add mutex to all only, parse_data_file crash with deadlock error, because it's use all method inside yourself - self.create(nil) do |emoji|. I can re-write create method, something like this, it's allow to use mutex only one time :

def create(name)
    emoji = Emoji::Character.new(name)
    if defined? @all
      @all << edit_emoji(emoji) { yield emoji if block_given? }
    else
      self.all << edit_emoji(emoji) { yield emoji if block_given? }
    end
    emoji
  end

About populate all emoji to memory - we think it's a great idea!

[myxaluch]

@mislav Hello again!
What about your sentence to load all emoji as soon as library loads? Could I take it on myself or you've already started work on it?

[mislav]

@myxaluch Yes, please open an alternative PR with the approach of preloading all emoji at load. I think that's a much safer and simpler approach, and would make multithreading faster since no mutex will be needed.

[myxaluch]

@mislav OK