I am new to the concept of yield and currently practising it.
I was expecting to get ["bread", "JUICY", "bread"]
but I got ["bread", "steak", "bread"].
Can you please help me understand why? And how can I fix my code?
def burger(patty)
if block_given?
yield(patty)
end
return ["bread", patty, "bread"]
end
# TODO: Change 'steak'to 'JUICY'using yield
juicy_burger = burger("steak") do |patty|
patty = "JUICY"
end
p juicy_burger
juicy_burger = burger("steak") do |patty|
patty = "JUICY"
end
Reassignments like this are not propagated to the outer scopes. Once this block returns, patty "reverts" to its initial value.
Solution? Use the overwritten value while it's still in scope.
def burger(patty)
if block_given?
patty = yield(patty)
# ^ shadow the parameter here.
# doesn't have to be a shadow. You can use any name. new_patty = yield(patty)
end
return ["bread", patty, "bread"]
end
juicy_burger = burger("steak") do |patty|
"JUICY #{patty}" # <- simple return here
end
p juicy_burger # >> ["bread", "JUICY steak", "bread"]
The variable is local to the function and you did not save back the value yield returned. The code below will give you ["bread", "JUICY", "bread"]
def burger(patty)
if block_given?
patty = yield(patty) # <-- this is the diff
end
return ["bread", patty, "bread"]
end
# TODO: Change 'steak'to 'JUICY'using yield
juicy_burger = burger("steak") do |patty|
patty = "JUICY"
end
p juicy_burger
Related
Hi I have a string passed back from rspec.
It should show
"alias/public_html/ab1/ab2/"
but I am getting "\"alias/public_html/ab1/ab2/\""
I am getting the rspec error below:
WebServer::HttpdConf#alias_path returns the aliased path
Failure/Error: expect(httpd_file.alias_path('/ab/')).to eq 'alias/public_html/ab1/ab2/'
expected: "alias/public_html/ab1/ab2/"
got: "\"alias/public_html/ab1/ab2/\""
(compared using ==)
# ./spec/lib/config/httpd_conf_spec.rb:90:in `(root)'
And here is my actual program file
def alias_path(path)
#hash_httpd['Alias'][path]
end
Please help
EDIT
Sorry, I am new to RUby, here is the httpd_file
def initialize(httpd_file_content)
#hash_httpd = Hash.new
httpd_file_content.each_line do | line |
#commands = line.split
if #commands.length == 2
#hash_httpd[#commands[0]] = #commands[1]
else
if !#hash_httpd.has_key?(#commands[0])
al = Hash.new
#hash_httpd[#commands[0]] = al
else
al = #hash_httpd[#commands[0]]
end
al[#commands[1]] = #commands[2]
end
end
end
If you are sure that your alias_path output will be "alias/public_html/ab1/ab2/", then you can just modify your alias_path method definition by removing the quotes (if any) from the returned path:
def alias_path(path)
#hash_httpd['Alias'][path].gsub('"', '')
end
As a way to learn the ins and outs of ruby, I decided to make a (relatively simple) text-based RPG. Everything so far has gone well, except recently I've hit a roadblock that I haven't seen before.
My goal is: if any stat (str, def, agi, man) is < 0, I want to make it = 0. For some reason though, ruby doesn't seem to like the `<'.
Here's the code ruby hangs up on:
def self.compile
#str = ProfileData.load['g_str']
#def = ProfileData.load['g_def']
#agi = ProfileData.load['g_agi']
#man = ProfileData.load['g_man']
#smin = 1
#dmin = 1
#amin = 1
#mmin = 1
if #str < #smin
#str = 0
end
if #def < #dmin
#def = 0
end
if #agi < #amin
#agi = 0
end
if #man < #mmin
#man = 0
end
#str.round!
#def.round!
#agi.round!
#man.round!
d = YAML::load_file('./profile')
d['mstr'] = #str
File.open('./profile', 'w') {|f| f.write d.to_yaml}
d = YAML::load_file('./profile')
d['mdef'] = #def
File.open('./profile', 'w') {|f| f.write d.to_yaml}
d = YAML::load_file('./profile')
d['magi'] = #agi
File.open('./profile', 'w') {|f| f.write d.to_yaml}
d = YAML::load_file('./profile')
d['mman'] = #man
File.open('./profile', 'w') {|f| f.write d.to_yaml}
end
Now when I run through my program, I get this error code when it finally runs "compile":
start.rb:734:in `compile': undefined method `<' for []:Array (NoMethodError)
And that's it. Have any clue what's happened or how I can fix it? Any help is very much appreciated!
It means your variables (at leas one per compared pair) is of Array type.
Check what each of these
#str = ProfileData.load['g_str']
#ddef = ProfileData.load['g_def']
#agi = ProfileData.load['g_agi']
#man = ProfileData.load['g_man']
returns and make sure it is Comparable (integers, for example).
The load method seems to assume that would be a collection of variables, even you having just one.
If you grant to be always one, select just the first and as it may be a string you should make it a int.
#str = ProfileData.load['g_str'].first.to_i
I'm trying to define methods to parse through an apache log file and pull ip addresses, URLs, requests per hour, and error codes. I've got everything working outside of methods, but when attempting to put that code into the methods I keep getting the error message "Stack level too deep." Here is the code in question.
class CommonLog
def initialize(logfile)
#logfile = logfile
end
def readfile
#readfile = File.readlines(#logfile).map { |line|
line.split()
}
#readfile = #readfile.to_s.split(" ")
end
def ip_histogram
#ip_count = 0
#readfile.each_index { |index|
if (#readfile[index] =~ /\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/ )
puts #readfile[index]
puts #ip_count += 1
end
}
end
def url_histogram
url_count = 0
cleaned_file.each_index { |index|
if (cleaned_file[index] =~ /\/{1}(([a-z]{4,})|(\~{1}))\:{0}\S+/ )
puts cleaned_file[index]
puts url_count += 1
end
}
end
def requests_per_hour
end
def sorted_list
end
end
my_file = CommonLog.new("test_log")
cleaned_file = my_file.readfile
puts cleaned_file.ip_histogram
It looks like the problem lies on you CommonLog#readfile method:
def readfile
#readfile = File.readlines(#logfile).map { |line|
line.split()
}
#readfile = readfile.to_s.split(" ")
end
Notice that inside the implementation of readfile your calling readfile recursively? When it executes it reads the lines from the file, maps them and assign the result the #readfile; then it calls readfile and the method starts to execute again; this goes on forever, until you stack blows up because of too many recursive method calls.
I assume what you actually meant is:
#readfile = #readfile.to_s.split(" ")
I have constructed an Event Manager class that performs parsing actions on a CSV file, and produces html letters using erb. It is part of a jumpstart labs tutorial
The program works fine, but I am unable to call multiple methods on an object without the earlier methods interfering with the later methods. As a result, I have opted to create multiple objects to call instance methods on, which seems like a clunky inelegant solution. Is there a better way to do this, where I can create a single new object and call methods on it?
Like so:
eventmg = EventManager.new("event_attendees.csv")
eventmg.print_valid_phone_numbers
eventmg_2 = EventManager.new("event_attendees.csv")
eventmg_2.print_zipcodes
eventmg_3 = EventManager.new("event_attendees.csv")
eventmg_3.time_targeter
eventmg_4 = EventManager.new("event_attendees.csv")
eventmg_4.day_of_week
eventmg_5 = EventManager.new("event_attendees.csv")
eventmg_5.create_thank_you_letters
The complete code is as follows
require 'csv'
require 'sunlight/congress'
require 'erb'
class EventManager
INVALID_PHONE_NUMBER = "0000000000"
Sunlight::Congress.api_key = "e179a6973728c4dd3fb1204283aaccb5"
def initialize(file_name, list_selections = [])
puts "EventManager Initialized."
#file = CSV.open(file_name, {:headers => true,
:header_converters => :symbol} )
#list_selections = list_selections
end
def clean_zipcode(zipcode)
zipcode.to_s.rjust(5,"0")[0..4]
end
def print_zipcodes
puts "Valid Participant Zipcodes"
#file.each do |line|
zipcode = clean_zipcode(line[:zipcode])
puts zipcode
end
end
def clean_phone(phone_number)
converted = phone_number.scan(/\d/).join('').split('')
if converted.count == 10
phone_number
elsif phone_number.to_s.length < 10
INVALID_PHONE_NUMBER
elsif phone_number.to_s.length == 11 && converted[0] == 1
phone_number.shift
phone_number.join('')
elsif phone_number.to_s.length == 11 && converted[0] != 1
INVALID_PHONE_NUMBER
else
phone_number.to_s.length > 11
INVALID_PHONE_NUMBER
end
end
def print_valid_phone_numbers
puts "Valid Participant Phone Numbers"
#file.each do |line|
clean_number = clean_phone(line[:homephone])
puts clean_number
end
end
def time_targeter
busy_times = Array.new(24) {0}
#file.each do |line|
registration = line[:regdate]
prepped_time = DateTime.strptime(registration, "%m/%d/%Y %H:%M")
prepped_time = prepped_time.hour.to_i
# inserts filtered hour into the array 'list_selections'
#list_selections << prepped_time
end
# tallies number of registrations for each hour
i = 0
while i < #list_selections.count
busy_times[#list_selections[i]] += 1
i+=1
end
# delivers a result showing the hour and the number of registrations
puts "Number of Registered Participants by Hour:"
busy_times.each_with_index {|counter, hours| puts "#{hours}\t#{counter}"}
end
def day_of_week
busy_day = Array.new(7) {0}
d_of_w = ["Monday:", "Tuesday:", "Wednesday:", "Thursday:", "Friday:", "Saturday:", "Sunday:"]
#file.each do |line|
registration = line[:regdate]
# you have to reformat date because of parser format
prepped_date = Date.strptime(registration, "%m/%d/%y")
prepped_date = prepped_date.wday
# adds filtered day of week into array 'list selections'
#list_selections << prepped_date
end
i = 0
while i < #list_selections.count
# i is minus one since days of week begin at '1' and arrays begin at '0'
busy_day[#list_selections[i-1]] += 1
i+=1
end
#busy_day.each_with_index {|counter, day| puts "#{day}\t#{counter}"}
prepared = d_of_w.zip(busy_day)
puts "Number of Registered Participants by Day of Week"
prepared.each{|date| puts date.join(" ")}
end
def legislators_by_zipcode(zipcode)
Sunlight::Congress::Legislator.by_zipcode(zipcode)
end
def save_thank_you_letters(id,form_letter)
Dir.mkdir("output") unless Dir.exists?("output")
filename = "output/thanks_#{id}.html"
File.open(filename,'w') do |file|
file.puts form_letter
end
end
def create_thank_you_letters
puts "Thank You Letters Available in Output Folder"
template_letter = File.read "form_letter.erb"
erb_template = ERB.new template_letter
#file.each do |line|
id = line[0]
name = line[:first_name]
zipcode = clean_zipcode(line[:zipcode])
legislators = legislators_by_zipcode(zipcode)
form_letter = erb_template.result(binding)
save_thank_you_letters(id,form_letter)
end
end
end
The reason you're experiencing this problem is because when you apply each to the result of CSV.open you're moving the file pointer each time. When you get to the end of the file with one of your methods, there is nothing for anyone else to read.
An alternative is to read the contents of the file into an instance variable at initialization with readlines. You'll get an array of arrays which you can operate on with each just as easily.
"Is there a better way to do this, where I can create a single new object and call methods on it?"
Probably. If your methods are interfering with one another, it means you're changing state within the manager, instead of working on local variables.
Sometimes, it's the right thing to do (e.g. Array#<<); sometimes not (e.g. Fixnum#+)... Seeing your method names, it probably isn't.
Nail the offenders down and adjust the code accordingly. (I only scanned your code, but those Array#<< calls on an instance variable, in particular, look fishy.)
I implemeting async thread manager and I want to pass reference to thread, where it should save the results of his work. And then when all thread finished i will handle all results.
What I need is to know how to work with 'references'.
lets assume I have variable result (or hash[:result1]), I want to pass it to the thread like
def test_func
return 777;
end
def thread_start(result)
Thread.new do
result = test_func;
end
end
and I want is to get following result
result = 555
thread_start(result);
#thread_wait_logic_there
result == 777; #=> true
hash = {:res1 => 555};
thread_start(hash[:res1])
#thread_wait_logic_there
hash[:res1]==777 #=> true
what should I chnage in my code to make it work?
Ruby version is 1.9.3
You can pass entrire hash to function:
def test_func
return 777;
end
def thread_start(hash, key)
Thread.new do
hash[key] = test_func;
end
end
Then this will work:
hash = {:res1 => 555};
thread_start(hash, :res1)
hash[:res1]==777 #=> true
Also if you want to be sure that you getting result after computations finished you must wait for thread, like this:
hash = {:res1 => 555};
thread_start(hash, :res1).join
hash[:res1]==777 #=> true
Edit: Added key,join