I have a strange problem with the FastImage gem. When I try to access the variable directly or call methods on it, I get a nil error. Rails says that the variable doesn't exist, so something like FastImage.size(url)[0] won't work. However, if I use 'puts', i.e puts FastImage.size(url) the variable can be accessed.
In the console, everything is working fine. Any ideas?
images.each do |d|
puts FastImage.size(d["src"])[0] + FastImage.size(d["src"])[1]
results << d["src"]
end
Figured it out! What happens is that FastImage throws an error if there is a bad url, so one needs to check that the url is valid. What happened was that one of the urls was invalid, so it would throw an exception midway through the iteration.
Related
Upon submitting a form in Sinatra, I'm coming up with the following error:
App 40327 output: 2018-06-28 02:59:17 - NoMethodError - undefined method `[]' for nil:NilClass:
App 40327 output: /Library/WebServer/Documents/blammo/routes/publish.rb:87:in `block in <class:MyApp>'
The form is a file upload form, and a single text field. Simple. The file goes through, as does the text field. They are both captured just fine.
I submit the params to a method, which is ultimately responsible for generating the error on the following line down the page:
fname = params[:s_single_file_upload][:filename]
The method in question returns fine with a boolean. I've rewritten it a couple of ways and flushed out anything that might trip something I'm
unfamiliar with.
So the params is messed up if this method mentioned above is being called. So fname can't be assigned. I expect the params to be intact
at this point in the code. Is there any destruction if the params are perused before this point? In another language, I've seen params destroyed
in one way or another for some reason, but I'm not sure about Ruby.
I'm not finding any nil:NilClass, but that's exactly what it's reporting. Here's the trigger of this method:
result = Alpha::rf_alpha_sniff(params)
And the module::method:
module Alpha
def self.rf_alpha_sniff(incoming)
qualifiers = %w(alpha bravo charlie delta echo foxtrot)
incoming.delete('captures')
incoming.delete('splat') # take out Mustermann's 'captures' and 'splat'
incoming.delete('s_single_file_upload') # non-perusal 'single_file_upload'
incoming.values.each do |item|
item = item.gsub(" ","_")
Dev::hq_log("item: #{ qualifiers.include?(item.downcase) }")
return true if qualifiers.include?(item.downcase)
end
return false
end
end
So the page progresses fine without this method. When the method is induced any way, the params seem to get screwed up, so the file is pretty much
gone.
How is this method interfering with the params so that it's unavailable later on down the script? I'm expecting it to be fully available everywhere.
Turns out, using incoming.delete was deleting items from the params hash, as it was a reference to the original, instead of using a copy.
So, I have to copy the params by using params.dup (duplicate) so they are not the same object.
Having a view of the params hash post-testing-method, showed me that objects were indeed deleted. Another one solved.
Probably a stupid question but I was following along this article and came across a bit of code I couldn't quite grasp. Here it is:
class CreateArticle
attr_reader :validate_article, :persist_article
def initialize(validate_article, persist_article)
#validate_article = validate_article
#persist_article = persist_article
end
def call(params)
result = validate_article.call(params)
if result.success?
persist_article.call(params)
end
end
end
More specifically, the problematic line is this:
if result.success?
Here's my problem with it: where did the success? method come from? It's not default in Ruby, and result is a local variable, so it should be nearby. But even if it's just omitted in the code sample, where would it have to be defined for that line to work? Everywhere I tried to define it just gave me an 'undefined method' error.
For example, I tried to define it both in the CreateArticle class and in the (only alluded to) ValidateArticle class, the obvious culprits, but no dice.
Update:
The reason I ask is not so much about what success? does as it is because I'm interested in using the pattern in my code. So, for example, my version of the success? method could be just checking whether a value got updated, or an item was inserted into an array. For example, let's say it's just this:
def success? # or self.success?
return true
end
Problem is, I can find no place where I can put this that works. I even created a module just for it and included it into the class, and still it doesn't work (it just returns 'undefined method'). So I'm still at a loss as to where I would have to define such a method so that it would work the way it looks like it should.
It's a method that comes with rails. It checks.for a server response with a 200 code. If it gets a 200 code it returns true else it returns false. Read the rails API docs about it... https://apidock.com/rails/v3.2.3/ActiveResource/Response/success%3F
Actually . success? is a built in ruby method. Check here. What it actually does is checking Stat and returns a boolean.
I did some more digging around the blog and from what I found I suspect that the code is probably making use of the dry-monads gem:
You can explicitly check the type by calling failure? or success? on a monadic value.
It's not explicit in the code excerpt but it's the only thing that makes sense.
I have this Ruby code in a script:
$dev_input=gets.chomp.downcase!
if $dev_input.include? "/"
check_developer_commands()
else
puts ">>Invalid Command<<"
continuing_dev_mode()
end
The problem is, whenever I try and run the script containing this, I get an error spat back at me that says :
dev_continue_main.rb:3:in 'continuing_dev_mode': undefined method 'include?' for nil:NilClass (NoMethodError)
Any idea what this error might be? I'm pretty sure that this is the proper way to use the .include? method. I've done some research, looked at tutorialspoint.com and some other sites, but they agree that this is the proper way to use this method.
I checked the error message and it confirmed that the third line in this script/my example is the source of the problem, so it's not some other instance of this method throwing an error.
Any thoughts? Please Help!
The problem is that $dev_input is nil. That stems from applying downcase! in defining $dev_input. I don't know why you want to possibly assign nil to $dev_input, and at the same time claim that calling include? on it is the right way. I don't get your intention for doing that, but if you instead had $dev_input = gets.chomp.downcase, then it wouldn't cause such error.
I was looking at Sinatra and trying to understand the syntax:
require 'sinatra'
get '/' do
"Hello, World!"
end
I understand it does this:
This is a ‘Route’. Here, we’re telling Sinatra that if the home, or root, URL '/' is requested, using the normal GET HTTP method, to display “Hello, World!”
But what is happening the Ruby language?
What does this syntax mean: get '/'? Is get a method and '/' a parameter to it? If it is method, then in Ruby, I can call a method as methodname (parameter) {}. What is { } there for?
I usually understand do and end as { }, which are kinds of enclosures to function bodies.
Between do and end we have "Hello, World!" so is it a statement? What I mean is, it is getting printed, but we did not call it as print "Hello, World!", so what is going on?
It seems get is a method defined in Sinatra, but if I add a gem, where there is a get method already defined, then how do I know which 'get' method it would call? Or, does it refer to the HTTP get method?
I am sorry if this question sounds very basic, but I want to get through it before I move forward.
May I suggest going through a tutorial on ruby before tackling a larger problem like sinatra which is a fairly specialized library.
A good place to start is with the Ruby Koans
As for your questions.
get is a method. '/' is its argument. and do ... end denotes a block in ruby just like {} would.
Yeah that's what do ... end are
Blocks in Ruby return the last value calculated by default so in the is case having a string is the same as having return "String".
If you are getting a namespace collision, Ruby will complain. In this case get is the sinatra defined method get. Abstractly it stands for an HTTP GET request against the server.
For the "perfect" response, I suggest you have a look at the book "Sinatra Up and Running" by
Alan Harris and Konstantin Haase.
http://shop.oreilly.com/product/0636920019664.do
Pages 6 and 7 explain how the line "get '/' do" is in fact a method call.
And you can view this 2 pages with Google Preview.
Each time I add in the correct code, it gives me the same error due to AboutMethods:0x00000101841a28 number changing each time. It's like its stuck and I don't know how to get out this loop. It worked once, then I went on to the next step, but then it triggered an error after that.
I must not be inputting the correct line of code given from the console?
def test_calling_private_methods_with_an_explicit_receiver
exception = assert_raise(NoMethodError) do
self.my_private_method
end
assert_match "private method `my_private_method' called for #<AboutMethods:0x000001008debf8>", exception.message
end
The AboutMethods:0x000001008debf8 changes each time, not sure how to approach this problem?
AboutMethods:0x... is the output of the inspect method, which usually (and in this case) includes the class name (AboutMethods) and the object id (0x...). The object id is related to the objects location in memory, so it will change every time.
In my experience, there is very little value to checking the string from an exception (it's brittle). However, if you feel the need, use a regex:
assert_match /private method `my_private_method' called for \#\<AboutMethods:.*/