Yet another JSON iterator
YAJI is a ruby wrapper to YAJL providing iterator interface to streaming JSON parser.
INSTALL
This gem depends on yajl. So you need development headers installed on your system to build this gem. For Debian GNU/Linux family it will be something like:
sudo apt-get install libyajl-dev
Now you ready to install YAJI gem:
gem install yaji
USAGE
YAJI::Parser initializer accepts IO instance or String.
require 'yaji'
YAJI::Parser.new('{"foo":"bar"}')
YAJI::Parser.new(File.open('data.json'))
There is integration with curb, so you can pass Curl::Easy instance to
as input for parser.
require 'curl'
curl = Curl::Easy.new('http://avsej.net/test.json')
parser = YAJI::Parser.new(curl)
parser.each.to_a.first #=> {"foo"=>"bar", "baz"=>{"nums"=>[42, 3.1415]}}
There no strict requirement though, it could be any instance responding
to #on_body and #perform.
Parser instance provides two iterators to get JSON data: event-oriented
and object-oriented. YAJI::Parser#parse yields tuple `[path, event,
value] describing some parser event. For example, this code
parser = YAJI::Parser.new('{"foo":[1, {"bar":"baz"}]}')
parser.parse do |path, event, value|
puts [path, event, value].inspect
end
prints all parser events
["", :start_hash, nil]
["", :hash_key, "foo"]
["foo", :start_array, nil]
["foo/", :number, 1]
["foo/", :start_hash, nil]
["foo/", :hash_key, "bar"]
["foo//bar", :string, "baz"]
["foo/", :end_hash, nil]
["foo", :end_array, nil]
["", :end_hash, nil]
You can call #parse method without block and it will return
Enumerator object.
The another approach is to use YAJI::Parser#each method to iterate
over JSON objects. It accepts optional filter parameter if you'd like to
iterated sub-objects. Here is the example
parser = YAJI::Parser.new('{"size":2,"items":[{"id":1}, {"id":2}]}')
parser.each do |obj|
puts obj.inspect
end
will print only one line:
{"size"=>2, "items"=>[{"id"=>1}, {"id"=>2}]}
But it might be more useful to yield items from inner array:
parser = YAJI::Parser.new('{"size":2,"items":[{"id":1}, {"id":2}]}')
parser.each("/items/") do |obj|
puts obj.inspect
end
code above will print two lines:
{"id"=>1}
{"id"=>2}
You can use this iterator when the data is huge and you'd like to allow
GC to collect yielded object before parser finish its job. You can also
specify additional selector if you need to fetch some sibling nodes,
e.g. "size" from previous example:
parser = YAJI::Parser.new('{"size":2,"items":[{"id":1}, {"id":2}]}')
parser.each(["size", "/items/"]) do |obj|
puts obj.inspect
end
it yields
2
{"id"=>1}
{"id"=>2}
Parse objects in top-level array. Without any parameters parser will produce single object for the input:
parser = YAJI::Parser.new('[{"id":1}, {"id":2}]')
parser.each do |obj|
puts obj.inspect
end
Output:
[{"id"=>1}, {"id"=>2}]
But you and interate over inner objects passing "/" as the argument:
parser = YAJI::Parser.new('[{"id":1}, {"id":2}]')
parser.each("/") do |obj|
puts obj.inspect
end
Output:
{"id"=>1}
{"id"=>2}
LICENSE
Copyright 2011 Couchbase, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.