This document introduces BLDR, a JSON templating DSL created by Alex Sharp for use at Zaarly. BLDR allows defining JSON responses through a simple declarative API, with support for objects, collections, attributes, nesting, and custom handlers. It aims to provide more control over JSON responses than using #as_json directly in Ruby on Rails.

1. BLDR
Minimalist JSON templating DSL
Alex Sharp
@ajsharp
Friday, September 30, 2011

2. WHO AM I?
Alex Sharp (@ajsharp)
Ruby Engineer at Zaarly (zaarly.com)
Friday, September 30, 2011

3. WHAT IS ZAARLY?
Buyer-centric local commerce platform
Heavily api driven (iOS, Android, Web, HTML5 mobile)
API only speaks json
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4. WHY BLDR?
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5. LET ME COUNT THE REASONS
#as_json quickly gets...unwieldy
We need tight control over our json responses
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6. SECURITY EXPLOIT
We were leaking information in our json documents we
weren’t aware of
We didn’t understand #as_json was recursing through
relationships and serializing them
Not good...
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7. TECHCRUNCH STORY
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8. BLDR
We wanted a simple, declarative DSL for defining JSON
responses
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9. BLDR
Simple, declarative DSL
Works with Sinatra
Rails 3 support nearly complete
Four DSL methods (object, collection, attribute, attributes)
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10. SINATRA
get '/foo' do
bar = 'baz'
bldr :foo, :locals => {:bar => bar}
end
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11. SINATRA
# foo.bldr
object do
attribute :foo, bar
end
# output
{"foo": "baz"}
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12. ATTRIBUTE LISTS
object :post => post do
attributes :title, :body
end
{ "post": {
"title": "my title",
"body": "..."
}
}
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13. IMPLIED OBJECTS
object :post do
attributes :title, :body
end
{ "post": {
"title": "my title",
"body": "..."
}
}
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14. DYNAMIC ATTRIBUTES
object :post do
attribute :comment_count do |post|
post.comments.count
end
end
{ "post": {"comment_count":1} }
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15. OBJECT NESTING
object :post => post do
attributes :title, :body
object :author => post.author do
attribute :last_name
end
end
{ "post": {
"title": "my title",
"body": "...",
"author": {"last_name": "Doe"}
}
}
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16. ATTRIBUTE ALIASES
object :post => post do
attributes :title, :body
object :author => post.author do
attribute :surname => :last_name
end
end
{ "post": {
"title": "my title",
"body": "...",
"author": {"surname": "Doe"}
}
}
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17. TOP-LEVEL COLLECTIONS
collection :posts => posts do
attributes :title, :body
attribute :comment_count { |post| post.comments.count }
end
{ "posts": [
{ "title": "my title",
"comment_count": 2,
}
]}
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18. NESTED COLLECTIONS
collection :posts => posts do
collection :comments => current_object.comments do
attributes :body, :author, :email
end
end
{ "posts": [
{ "comments": [
{ "body": "...",
"author_name": "Comment Troll",
"email": "troll@trolling.edu" }
]}
]}
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19. OTHER FEATURES
Uses multi_json gem -- pick your encoding library
Bldr.handler
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20. Bldr.handler BSON::ObjectId do |value|
val.to_s # => "4e77a682364141ecf5000002"
end
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21. MORE INFO
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22. MORE INFO
github.com/ajsharp/bldr
@ajsharp
ajsharp@gmail.com
zaarly.com / alexjsharp.com
Friday, September 30, 2011