Add trailing comma and bracket to Ruby JSON - ruby-on-rails

Question

I need to add commas between my hashes and encapsulate them inside square brackets. Can anyone tell me how?
Here is my code:
namespace :fieldfacts do
desc "Export Topics"
task :export_topics => :environment do
out = []
File.open("public/topics.json","w") do |f|
Topic.all.each do |topic|
api = TopicsService.new()
topic_api = api.get(topic.topic_api_id)
out = {
'id' => topic.id,
'name' => topic.name,
'keywords_list' => topic_api.keywords_list,
'organizations_list' => topic_api.organizations_list,
'social_groups_list' => topic_api.social_groups_list,
'feeds_list' => topic_api.feeds_list,
'articles_list' => topic_api.articles_list,
'people' => topic_api.people
}
f.write(JSON.pretty_generate(out))
end
end
end
end
Here is the output:
{
"id": 3,
"name": "Precision Agriculture",
"keywords_list": null,
"organizations_list": null,
"social_groups_list": null,
"feeds_list": null,
"articles_list": null,
"people": null
}{
"id": 4,
"name": "Backcountry Skiing",
"keywords_list": null,
"organizations_list": null,
"social_groups_list": null,
"feeds_list": null,
"articles_list": null,
"people": null
}
Any help would be appreciated. Thanks!

Answer 1

Your issue here is that you are generating JSON multiple times and then appending it together, rather than generating it once.
Something like this should solve your problem (note the change in location of f.write):
namespace :fieldfacts do
desc "Export Topics"
task :export_topics => :environment do
out = []
File.open("public/topics.json","w") do |f|
Topic.all.each do |topic|
api = TopicsService.new()
topic_api = api.get(topic.topic_api_id)
out << {
'id' => topic.id,
'name' => topic.name,
'keywords_list' => topic_api.keywords_list,
'organizations_list' => topic_api.organizations_list,
'social_groups_list' => topic_api.social_groups_list,
'feeds_list' => topic_api.feeds_list,
'articles_list' => topic_api.articles_list,
'people' => topic_api.people
}
end
f.write(JSON.pretty_generate(out))
end
end
end