I'm trying to get all of my prices in my array of URLS, getting the values with a CSS selector.
The thing is, the method at_css is giving me the following error:
undefined method `at_css' for string (NoMethodError)
Can anyone help me? Thanks
test = ["www.myweb.com/1", "www.myweb.com/2"]
test.each do |item|
Nokogiri::HTML(open(item))
puts item.at_css('.itemprice').text
puts item.at_css('.description').text
puts "Empty Line"
end
The item variable in your block is a string i.e. an element from your test array variable. And strings don't have a to_css method in Ruby. You probably wanted to call the to_css on some Nokogiri-related object.
I think you need the following:
some_var = Nokogiri::HTML(open(item))
some_var.at_css('.itemprice').text
Related
i am a newbie in ruby... I'm trying to convert media into a scorm package using what i found on github but i got an error while trying to run the script in the command prompt undefined method `gsub' for nil:NilClass. I guess it may be due to a defined method. any idea on how i can remove this error ?
dir = ARGV.shift.gsub(/\/+$/, '')
index = nil
media = []
Dir["#{dir}/media/*.json"].each do |file|
id = JSON.parse(File.read(file))
base = file.gsub(/\/media\/.*\.json$/, '')
index = "#{base}/index.html"
name = File.basename file
media.push [name,id]
puts "#{name}: #{id}"
end
As the error says, you are calling the method gsub on an object that is an instance of NilClass, in other words you are calling gsub on nil.
The error message tells you in which method and on which line this happens and how you got to that line of code. You will have to examine the error message to find the place in your code where you are calling gsub on an object that is nil, then you have to examine your code to find out why that object is nil instead of a String as you expect it to.
I'm trying to run this code"
FACTORY = %w(ProcessedTransaction Chargeback).freeze
FACTORY.constantize.each do |factory|
factory.public_send(:delete_all)
end
end
But I get this error: NoMethodError: undefined methodconstantize' for #`
Do you know how I can solve the issue?
In ruby uppercased variables are constants by default so you can't call constantize on it. In your case it's just an array so this should work:
FACTORY = %w(ProcessedTransaction Chargeback).freeze
FACTORY.each do |factory|
factory.constantize.public_send(:delete_all)
end
You can call String#constantize only on strings but you are calling it on array FACTORY.
Remove FACTORY.constantize and add factory.constantize.public_send(:delete_all)
Also make sure you have ActiveSupport::Inflector required
First of all, I know it has been posted, I've seen most of the question posts but I still don't understand how it works.
So I'm getting the error:
Script 'Terrain Tag Detection ~' line 115: NoMethodError occurred.
undefined method '[]' for nil:NilClass
My 'Terrain Tag Detection ~' Script looks like this: http://pastebin.com/PUypTwJs (can't paste the code here correctly, and yes it's about Pokemon).
That means your #map = WildPokemon.fetch($game_map.map_id) method doesn't return and value and you want to access #map variable.
You can add a check in your code like below:
#map = WildPokemon.fetch($game_map.map_id)
if #map.present?
#enemy = #map[0][rand(#map[0].size)]
#level = #map[1][rand(#map[1].size)]
end
I recently had cause to use the nokogiri gem to parse html but while i going through their documentation, i came across this ruby syntax that i hadn't seen before
html_doc = Nokogiri::HTML('<html><body><h1>Mr. Belvedere Fan Club</h1></body></html>')
xml_doc = Nokogiri::XML('<root><aliens><alien><name>Alf</name></alien></aliens></root>')
The part of interest for me is Nokogiri::HTML('...'). This looks very much like a method invocation but i know ruby method names cannot be in capital letters. So i looked through code files nokogiri gem and i came across the following definition
module Nokogiri
class << self
###
# Parse HTML. Convenience method for Nokogiri::HTML::Document.parse
def HTML thing, url = nil, encoding = nil, options = XML::ParseOptions::DEFAULT_HTML, &block
Nokogiri::HTML::Document.parse(thing, url, encoding, options, &block)
end
end
# more code
end
I tried reproducing the same code
module How
class << self
def DOESTHISWORK
puts "In How Method"
end
end
end
How::DOESTHISWORK
But it keeps coming back with the error "uninitialized constant How::DOESTHISWORK (NameError)". I know it has to do with the method name starting in capitals but i just haven't been able to figure out how it works in nokogiri.
The difference is in the Nokogiri example the method is being called with parentheses and a parameter value which identifies it as a method call. Your DOESTHISWORK method takes no parameters but can be called with empty parentheses e.g.
irb(main):028:0> How::DOESTHISWORK()
In How Method
=> nil
If you add a parameter to your method that can also serve to identify it as a method like so:
irb(main):036:0> How::DOESTHISWORK 'some param'
Starting method names with a lowercase letter is good practice but isn't enforced. Something that begins with a capital letter is assumed to be a constant and will be looked up as such, this is why the parentheses or parameter is needed to indicate a method is being referred to. Another example:
irb(main):051:0> def Example
irb(main):052:1> puts "An example!"
irb(main):053:1> end
=> nil
irb(main):054:0> Example
NameError: uninitialized constant Example
from (irb):54
from /Users/mike/.rbenv/versions/1.9.3-p194/bin/irb:12:in `<main>'
irb(main):055:0> Example()
An example!
=> nil
I also found this post to be very helpful
What are the restrictions for method names in Ruby?
It's good practice, while not mandatory, to start the method name with
a lower-case character, because names that start with capital letters
are constants in Ruby. It's still possible to use a constant name for
a method, but you won't be able to invoke it without parentheses,
because the interpeter will look-up for the name as a constant
erb gives me undefined local variable or method for main:Object (NameError) unless the variable used in erb template is a global variable.
Is that correct? on ruby 1.8.7 (2010-01-10 patchlevel 249) [i486-linux]
Below is code that works. If I remove $ from the variable name ($db, $db_root, $db_root_password) I get the error.
$db = get_single_argument("database name")
$db_root = get_single_argument("database root user name")
$db_root_passwd = get_single_argument("database root user password")
mysql_commands = get_conf_file("installer_mysql.erb")
puts mysql_commands.result #gives me the error
and get_conf_file procedure
def get_conf_file(file)
return_array = Array.new
if (File.exists?(file))
return_array = ERB.new File.read(file)
end
return_array
end
Ruby has a concept called a binding, which you might think of as the local variables, value of self, block etc. that a piece of code might have. You might also think of a binding as the code's context.
Erb's result method takes an optional second method which is the binding with which to evaluate the code you give it, so you can do stuff like
x = 1
ERB.new('x=<%= x %>').result(binding) #=> "x=1"
You're not passing in the binding of the caller, and you should be:
puts mysql_commands.result(binding)
The binding contains all the variable references in the current scope.