Still new to Ruby - I apologize in advance if this has been asked.
I am using HTTParty to get data from an API, and it is returning an array of JSON data that I can't quite figure out how to parse.
#<Net::HTTPOK:0x1017fb8c0>
{"ERRORARRAY":[],"DATA":[{"ALERT":1,"LABEL":"hello","WATCHDOG":1},{"LABEL":"goodbye","WATCHDOG":1}
I guess the first question is that I don't really know what I am looking at. When I do response.class I get HTTParty::Response. It appears to be a Hash inside an array? I am not sure. Anyway, I want a way to just grab the "LABEL" for every separate array, so the result would be "hello", "goodbye". How would I go about doing so?
you don't need to parse it per say. what you could do is replace ':' with '=>' and evaluate it.
example: say you have ["one":"a","two":"b"], you could set s to equal that string and do eval s.gsub(/^\[/, '{').gsub(/\]$/, '}').gsub('":', '"=>') will yield a ruby hash (with inspect showing {"one"=>"a", "two"=>"b"})
alternatively, you could do something like this
require 'json'
string_to_parse = "{\"one\":\"a\",\"two\":\"b\"}"
parsed_and_a_hash = JSON.parse(string_to_parse)
parsed_and_a_hash is a hash!
If that's JSON, then your best bet is to install a library that handles the JSON format. There's really no point in reinventing the wheel (although it is fun). Have a look at this article.
If you know that the JSON data will always, always be in exactly the same format, then you might manage something relatively simple without a JSON gem. But I'm not sure that it's worth the hassle.
If you're struggling with the json gem, consider using the Crack gem. It has the added benefit of also parsing xml.
require 'crack'
my_hash_array = Crack::JSON.parse(my_json_string)
my_hash_array = Crack::XML.parse(my_xml_string)
Related
This does what I want, but going via to_ruby seems unnecessary:
doc = Psych.parse("foo: 123")
doc.to_ruby.to_yaml
# => "---\nfoo: 123\n"
When I try to do this, I get an error:
DEV 16:49:08 >> Psych.parse("foo: 123").to_yaml
RuntimeError: expected STREAM-START
from /opt/…/lib/ruby/2.5.0/psych/visitors/emitter.rb:42:in `start_mapping'
I get the impression that the input needs to be a stream of some sort, but I don't quite get what incantation I need. Any ideas?
(The problem I'm trying to solve here, by the way (in case you know of a better way) is to fix some YAML that can't be deserialised into Ruby, because it references classes that don't exist. The YAML is quite complex, so I don't want to just search-and-replace in the YAML string. My thinking was that I could use Psych.parse to get a syntax tree, modify that tree, then dump it back into a YAML string.)
Figured out the incantation after finding the higher-level docs at https://ruby-doc.org//stdlib-2.3.0_preview1/libdoc/psych/rdoc/Psych/Nodes.html, though please let me know if there's a better way:
doc = Psych.parse("foo: 123")
stream = Psych::Nodes::Stream.new
stream.children << doc
stream.to_yaml
# => "foo: 123\n"
I'm trying to grab some data from last.fm and use it in a simple sinatra app. I've worked out how to open the document but having issues extracting the data in ruby here is the first list of the API data I'd like to grab the name:
{"similarartists":{"artist":[{"name":"Sonny & Cher"}]}
This is just an extract of the return, I'm using this in my rb file:
require 'json'
require 'open-uri'
data = JSON.parse(open("http://ws.audioscrobbler.com/2.0/?method=artist.getsimilar&artist=editors&api_key=xxx&format=json").read)
puts data["similarartists"]["artist"]["name"]
It doesn't seem to be working I get can't convert String into Integer (TypeError) on ruby 1.9.3 but the name in the JSON isn't an integer? If I just put the following:
puts data["similarartists"]["artist"]
It returns the whole thing, but I want to grab inside of that and get the name.
"name"=>"Interpol"
I don't understand why it would complain about integers when the name is a string? Hope someone can help me!
Based on the comments thread, the issue is a misunderstanding of the structure of the data returned from the API call.
The exact issue was the structure had an array of artists under the artist key so to get at the name you need to do:
data['similarartists']['artist'][0]['name']
Note though that you should only do that if you are sure there will only be one artist. The nature of the return data suggests that won't always be the case so you might be better off pulling all names depending on your use doing something like:
data['similarartists']['artist'].map {|a| a['name']}.join(',')
That will join all of the artist names together comma separated.
In the future, you can track this issue down by looking at the full structure of the return data and making sure you see the correct structure. The docs on the API may indicate some help here too.
You also might check if someone has made a gem for accessing the API. Often a gem will up-level some of this raw output and give you a nice object to work with. I suggest searching GitHub for a last.fm gem.
The problem is that you are trying to access an Array with the index "name", Ruby tries to convert this to an Integer and fails which results in the Error message you are seeing.
If you test the class of data["similarartists"]["artist"].class you will see that it returns Array. So basically what is happening is that the JSON.parse() called created as the value of data["similarartists"]["artist"] an Array of Hashes. To access all of the artist names you can simply iterate through this array:
require 'json'
require 'open-uri'
data = JSON.parse(open("http://ws.audioscrobbler.com/2.0/?method=artist.getsimilar&artist=editors&api_key=29da5a0e01ca2d1524cac596d5462d67&format=jso\
n").read)
# iterate through the Array of returned artists and print their names
data["similarartists"]["artist"].each do |artist|
puts artist["name"]
end
# output
# Interpol
# White Lies
# The Cinematics
# Smith & Burrows
# The National
# Julian Plenti
# She Wants Revenge
# etc ...
If you only want the first entry for Interpol you can just use index [0]:
puts data["similarartists"]["artist"][0]["name"]
I'm having an awful time trying to use a library to parse an XML File into a hash like object, modify it, then print it back out to another XML file in Ruby. For a class I'm taking, we're supposed to use a Java JAXB like library where we convert XML into an object. We've already done SAX and DOM methods so we can't use those methods of XML de-serialization. Nokogiri helped me with both of these in Ruby.
The only problem is that besides the SIMPLE modifications I'm making to the objects, when I write to file it has drastic differences. Is there a Ruby library meant for doing just this? I've tried: ROXML, XML::Mapping, and ActiveSupport::CoreExt. The only one I can get to even run is ActiveSupport, and even then it starts putting element attributes as child elements in the output XML.
I'm willing to try out XmlSimple, but I'm curious has anyone actually had to do this before/run into the same problems? Again, I can't read in lines one at a time like SAX or build a Tree like structure like DOM, it needs to be a hash like object.
Any help is much appreciated!
You should have a look into nokogiri: http://nokogiri.org/
Then you can parse the XML like this :
xml_file = "some_path"
#xml = Nokogiri::XML(File.open xml_file)
#xml.xpath('//listing').each do |node|
style = node.search("style").text
end
With Xpath, you can perform queries in the XML :
#xml.xpath("//listing[name='John']").first(10)
OK, I got it working. After looking at ActiveSupport::CoreExt 's source code I found it just uses a gem called xml-simple. What's obnoxious is the gem, library name in the require statement, and class name are a mixture of hyphenated and non hyphenated spellings. For future reference here's what I did:
# gem install xml-simple
# ^ all lowercase, hyphenated
require 'xmlsimple'
# ^ all lowercase, not hyphenated
doc = XmlSimple.xml_in 'hw3.xml', 'KeepRoot' => true
# ^ Camel cased (it's a class), not hyphenated
# doc.class => Hash
# manipulate doc as a hash
file = File.new('HW3a.xml', 'w')
file.write("<?xml version='1.0' encoding='utf-8'?>\n")
file.write(XmlSimple.xml_out doc, 'KeepRoot' => true)
I hope this helps someone. Also make sure you pay attention to case and hyphens with this gem!!!
I have a general idea of how I can do this, but can't pinpoint how exactly to get it done. I am sure it can be done with a regex of some sort. Wondering if anyone here can point me in the right direction.
If I have a string of html such as this
some_html = '<div><b>This is some BOLD text</b></div>'
I want to to divide it into logical pieces, and then put those pieces into an array so I end with a result like this
html_array = ["<div>", "<b>", "This is some BOLD text", "</b>","</div>" ]
Rather than use regex I'd use the nokogiri gem (a gem for parsing html written by Aaron Patterson - contributor to Rails and Ruby). Here's a sample of how to use it:
html_doc = Nokogiri::HTML("<html><body><h1>Mr. Belvedere Fan Club</h1></body></html>")
You can then call html_doc.children to get a nodeset and work your way from there
html_doc.children # returns a nodeset
Use an HTML parser, for instance, Nokogiri. Using SAX you can add tags/elements to the array as events are triggered.
It's not a good idea to try to regex HTML, unless you're planning to treat only a small determined subset of it.
some_html.split(/(<[^>]*>)/).reject{|x| '' == x}
What's the best library to use to convert the HTTP POST string received from a browser into a Ruby hash? I don't want to use the large rails-based libraries. I am using eventmachine and evma_httpserver, and want to include the lightest library possible that will decode and convert the params string.
Note: I don't need a webserver. I have the encoded post string in hand, and just need to convert it to a hash.
URI.decode_www_form from the Ruby standard library can do this: http://rubydoc.info/docs/ruby-stdlib/1.9.2/URI#decode_www_form-class_method
You could use the rack gem for its Rack::Utils.parse_query method.
If you want lighter than that, you could just copy the source code to the parse_query and unescape methods from it.
If you want event lighter (but perhaps not as performant or robust) than that, just implement your own split and lean on CGI.unescape.
Try this:
require "uri"
result = URI.decode_www_form("your=post¶ms=values").inject({}) {|r, (key,value)| r[key.to_sym] = value;r}
puts result[:your]
puts result[:params]