I wrote a very simple User class. The instance variable email has a reader accessor and my own writer accessor that validates the email address with a regex.
class User
attr_reader :email
def email=(value)
if (value =~ /^[a-z\d\-\_\+\.]+#([a-z\d\-]+\.)+[a-z]+$/)
#email = value
else
# bonus question: is ArgumentError the right error type to use here?
raise ArgumentError, "#{value} is not a valid email address."
end
end
end
I wrote the following test:
require 'test/unit'
require_relative '../lib/user'
class TC_UserTest < Test::Unit::TestCase
def setup
#user = User.new()
end
def test_email
# using the writer accessor
#user.email = 'user#example.com'
# bypassing the writer accessor. evil.
#user.email[4] = '#'
assert_equal('user#example.com', #user.email)
end
end
By using the reference given to me by the reader accessor, I am able to manipulate the email instance variable without going through the writer accessor.
The same principe would apply to any data type that allows manipulation without outright assigning a new value with =
Am I being overzealous? I just want to write robust code. Is there a way to ensure that my email address can only be set using the writer accessor?
I'm new to the language and I'm trying to get a feel for the best practices.
An option to make the test pass (and protect the #email variable) is to expose a duplicate.
def email
#email.dup
end
To do what you're trying to do, my advice is to move the regexp into its own validation method.
Better still, don't write an email regexp unless you really want to do it right.
Use a gem instead: https://github.com/SixArm/sixarm_ruby_email_address_validation
After you set the email, freeze it with http://ruby-doc.org/core-1.9.3/Object.html#method-i-freeze
Bonus answer: yes, ArgumentError is the right error type in general. If you're using Rails, consider using the Rails validation methods.
You can freeze value in writer, that way you'll be able to assign new one via writer, but already assigned would be immutable:
class User
attr_reader :email
def email=(value)
if (value =~ /^[a-z\d\-\_\+\.]+#([a-z\d\-]+\.)+[a-z]+$/)
# make email immutable:
#email = value.freeze
else
# bonus question: is ArgumentError the right error type to use here?
raise ArgumentError, "#{value} is not a valid email address."
end
end
end
Related
This is a fake banking app:
class Bank
private def initialize
$login = Hash.new
puts "Welcome to HEIDI BANK!"
end
def add(keyVal)
keyVal.each do |key, value|
$login[key] = value
end
end
def NewUser
puts "What is the name of the user you would like to add?"
user = gets.chomp
puts "What is the password you would add?"
pass = gets.chomp
passsym = pass.to_sym
$login.add(user => passsym)
end
end
you_bank = Bank.new
you_bank.NewUser
When I attempt to run it, I get:
Welcome to HEIDI BANK!
What is the name of the user you would like to add?
12
What is the password you would add?
13
then an error is raised:
in `NewUser': undefined method `add' for {}:Hash(NoMethodError)
How would I fix this error? It seems I might have to figure out how to call Bank.add or something. Do hashes have an add function built in, like with samp_array.push for arrays?
You defined add as an instance method of Bank, but you are calling it on $login, which is an instance of Hash. Call it on the instance of Bank itself, which can be omitted:
def NewUser
...
add(user => passsym)
end
I already provided the answer in the comments but I wanted to make a longer form answer to help you out. It appears that you're a young programmer and new to Ruby so I would like to help you adopt healthy habits. Accordingly, I have refactored your code and included comments explaining the changes with links to resources that you can read to help understand why the changes were made.
These are mostly minor issues but they're important when writing any kind of production code or when writing code that others may have to read or use in the future.
# Allows the use of STDIN.noecho which will not echo text input back to the console:
# https://stackoverflow.com/a/29334534/3784008
require 'io/console'
# Use two spaces of indentation for Ruby, not tabs and not 4 spaces:
# https://github.com/rubocop-hq/ruby-style-guide#source-code-layout
class Bank
# The initialize method is not a private method:
# https://stackoverflow.com/q/1567400/3784008
def initialize
# Use single quotes for non-interpolated strings
# https://github.com/rubocop-hq/ruby-style-guide#strings
puts 'Welcome to HEIDI BANK!'
# Don't instantiate the `login` variable here; it should be lazily instantiated:
# http://blog.jayfields.com/2007/07/ruby-lazily-initialized-attributes.html
end
# Use snake_case for method names
# https://github.com/rubocop-hq/ruby-style-guide#naming
def new_user
puts 'What is the name of the user you would like to add?'
user = gets.chomp
puts 'What is the password you would add?'
# Suppress local echo of the password as it is typed
# https://stackoverflow.com/a/29334534/3784008
pass = STDIN.noecho(&:gets).chomp
# Do not call .to_sym on pass; if pass == an Integer then it will raise an exception,
# e.g., 1.to_sym => NoMethodError: undefined method `to_sym' for 1:Integer
{ user => pass }
end
end
Then you run it like you were doing before:
you_bank = Bank.new
Welcome to HEIDI BANK!
=> #<Bank:0x00007f8cc9086710>
you_bank.new_user
What is the name of the user you would like to add?
foo
What is the password you would add?
=> {"foo"=>"bar"}
Two other notes on your original code:
Don't use global variables (variable name preceded with a $). There is more explanation at this answer. If you end up needing a variable that is accessible within the instance of the class you should use an instance variable.
Write DRY code. There's no need for the add(keyVal) method because it's implemented already in Hash by merge. Try translating the issue you want to resolve into something you can search for, in this case you want to "add to hash in ruby" and the first Google result for that query is this answer that details how to do that.
I hope this helps you out.
Update
Below you asked "what is lazy instantiation?" The short answer is: don't assign variables until they need to be used. For example:
# Bad; don't do this
class Foo
def initialize
# This variable is instantiated when calling `Foo.new`,
# before it needs to be used, and so takes up memory right
# away vs. only once it's needed
#variable_used_by_example_method = 'foobar'
end
def example_method
puts #variable_used_by_example_method
end
end
# Better; okay to do this
class Foo
def initialize
end
def example_method
# This variable is lazily instantiated, that is, it is not
# instantiated until `Foo.new.example_method` is called
#variable_used_by_example_method = 'foobar'
puts #variable_used_by_example_method
end
end
For your other question about comparing usernames and passwords against what users type in, I recommend you think through the problem and if you still are unsure then post a new question. The question you've asked isn't clear enough for me to give you a good answer. Right now you're experimenting with the code to figure out how everything works, and when you're experimenting and learning it's okay to do things that don't squarely fit into object-oriented programming design patterns. But any answer I give you based on what you've told me so far would either go against those patterns, or would be too advanced. (e.g., use a database and associated models in a framework like Rails)
I wouldn't do the first because that would be bad advice, and I wouldn't do the second because you should have a firmer grasp of Ruby and programming first. So my recommendation is for you to think these through:
What is the plain-English step-by-step explanation of your overall goal?
How can that explanation be described in terms of object-oriented logic?
What code can you write to encapsulate that logic?
What are the gaps between your ability to describe the logic and your ability to write code for that logic?
Then you can begin to ask specific questions to fill in those gaps.
I have two classes; customer and reservation. And my project is consist of only ruby code, not rails project.
Class reservation reads bulk json file line by line which includes customer hash.
From that hash, I create customer object.
Here's the code within the reservation class.
def parse_json
File.open(#filename, "r" ).each do |line|
#customers << Customer.new(JSON.parse(line))
end
return #customers
end
And in customer.rb I have the following;
validates_presence_of :hash
validate :hash_should_include_all_fields
attr_reader :name, :userid, :latitude, :longitude, :distance
def hash_should_include_all_fields
puts "I'm here #{hash}"
if hash.assert_valid_keys('user_id', 'name', 'latitude', 'longitude')
puts "Valid"
else
puts "Not valid"
end
end
However as I create customer objects, hash_should_include_all_fields method is not called.
What do I miss in here, that would be great if you can help.
Thanks
You're calling new which will build a Customer object but do nothing more.
Calling create! or create will also run validations and write the Object to the database if it's an active_record model.
If you don't want to write it to the databas you can call valid? on the instance created with new
I am receiving the following error when running my below ruby script:
s3parse.rb:12:in `block in <class:AccountLog>': undefined method `extract_account_id' for AccountLog:Class (NoMethodError)
I dont think it should be a class method, is there a reason its not taking my method into account?
class AccountLog
attr_accessor :bytes, :account_id, :date
def extract_account_id(line)
line.match(%r{accounts/(\d+)}).captures.join.to_i
end
s3log = File.open('vidcoder.txt').each do |line|
account_log = AccountLog.new
account_log.date = line.match(%r{\[[^:]*}).to_s.delete"[" #need to finish this regex to make it work
account_log.account_id = extract_account_id(line)
account_log.bytes = line.match(%r{^.*\s+HTTP.*\s+-\s+(\d+)\s+}).captures.join.to_i
puts "\n"
puts "The api request on #{account_log.date} was fromm account number #{account_log.account_id} and the bytes were #{account_log.bytes}"
end
end
def extract_account_id will define an instance method.
In the way you call it, you need a class method instead.
Define it like this:
def self.extract_account_id(line)
or, as you already have an AccountLog instance, use it to call extract_account_id:
account_log.account_id = account_log.extract_account_id(line)
Please note that with second way you do not need to alter method definition, just call extract_account_id via account_log instance.
And i guess you would want to put s3log = File... outside class definition.
Or use a constant instead: S3log = ...
Then you'll can access it as AccountLog::S3log
Is there any reason you don't think it should be a class method? You are using it in the context of a class method and that's why it it's saying no such method for class AccountLog.
If you name your method as self.extract_account_id(line) I'm sure it will work.
From what you are trying to do I think this is what you are looking for?
class AccountLog
attr_accessor :bytes, :account_id, :date
def self.extract_account_id(line)
line.match(%r{accounts/(\d+)}).captures.join.to_i
end
end
s3log = File.open('vidcoder.txt').each do |line|
account_log = AccountLog.new
account_log.date = line.match(%r{\[[^:]*}).to_s.delete"[" #need to finish this regex to make it work
account_log.account_id = extract_account_id(line)
account_log.bytes = line.match(%r{^.*\s+HTTP.*\s+-\s+(\d+)\s+}).captures.join.to_i
puts "\n"
puts "The api request on #{account_log.date} was fromm account number #{account_log.account_id} and the bytes were #{account_log.bytes}"
end
While you could take the class method approach, there seems to be a little more going on.
You should put the extraction logic in a method in itself rather than let it hangout in your class. Then outside of the class, have an instance of AccountLog where you can call on the methods for log and account id extraction. At that point you can do something with those values.
Class method or not is a detail we can explore after the class is a bit more clean I think.
I have a SchoolDay class that represents a school day: it can tell you the date, the semester, the term, the week, and the day. It can generate a string like "Sem1 13A Fri". To store these objects in the database, I want them serialized as a string.
Here is my DataMapper custom type code. I've sort of scraped ideas from the code in dm-types because (disappointingly) there is no real documentation for creating custom types. Sorry it's long.
module DataMapper
class Property
class SchoolDay < DataMapper::Property::String
#load_as ::SchoolRecord::DomainObjects::SchoolDay
# Commented out: the 'load_as' method is not found
def load(value)
# Take a string from the database and load it. We need a calendar!
val = case value
when ::String then calendar.schoolday(value)
when ::SR::DO::SchoolDay then value
else
# fail
end
end
def dump(value)
# Store a SchoolDay value into the database as a string.
case value
when SR::DO::SchoolDay
sd = value
"Sem#{sd.semester} #{sd.weekstr} #{sd.day}"
when ::String
value
else
# fail
end
end
def typecast(value)
# I don't know what this is supposed to do -- that is, when and why it
# is called -- but I am aping the behaviour of the Regexp custom type,
# which, like this one, stores as a String and loads as something else.
load(value)
end
# private methods calendar() and error_message() omitted
end
end
end
This code works for reading from the (SQLite) database, but not for creating new rows. The error message is:
Schoolday must be of type String
The code that defines the DataMapper resource and tries to create the record is:
class LessonDescription
include DataMapper::Resource
property :id, Serial
property :schoolday, SchoolDay # "Sem1 3A Fri"
property :class_label, String # "10"
property :period, Integer # (0..6), 0 being before school
property :description, Text # "Completed yesterday's worksheet. hw:(4-07)"
end
# ...
ld = LessonDescription.create(
schoolday: #schoolday,
class_label: #class_label,
period: #period,
description: description
)
Here is the code for the Regexp datamapper type in the dm-types library. It's so simple!
module DataMapper
class Property
class Regexp < String
load_as ::Regexp # NOTE THIS LINE
def load(value)
::Regexp.new(value) unless value.nil?
end
def dump(value)
value.source unless value.nil?
end
def typecast(value)
load(value)
end
end
end
end
For some reason, I cannot use the load_as line in my code.
To summarise: I am trying to create a custom type that translates between a SchoolDay (domain object) and a String (database representation). The translation is easy, and I've copied the code structure primarily from the DataMapper Regexp type. But when I try to save a SchoolDay, it complains that I'm not giving it a string. Frustratingly, I can't use the "load_as" method that the built-in and custom types all use, even though I have the latest gem. I can't find the "load_as" method defined anywhere in the source code for DataMapper, either. But it's called!
Sorry for the ridiculous length. Any help would be greatly appreciated, as would a pointer to a guide for creating these things that I have somehow missed.
It seems that the current code of dm-types at github hasn't made it to any official release -- that's why load_as doesn't work in your example. But try to add this method:
module DataMapper
class Property
class SchoolDay < DataMapper::Property::String
def custom?
true
end
end
end
end
That's working here.
Hi I have something like the folowing:
class TrialRequest
attr_accessor :trial_email
def initialize(email)
#trial_email = email
puts "Trial_email: #{trial_email}"
end
def create
#email = ::Gmail.connect!(gmail_name, gmail_password) do |gmail|
email = gmail.compose do
to 'trial#domain.com'
from trial_email
subject trial_email
text_part do
content_type 'text/html; charset=UTF-8'
body 'Sign me up.'
end
end
#binding.pry
gmail.deliver!(email)
end
end
end
The problem is that inside the compose block trial_email is not defined:
NameError: undefined local variable or method `trial_email' for #<Mail::Message:0x0000000431b830>
Is this a Ruby 1.9 issue or a gmail gem issue?
How should I go about making this method 'visible'/within the scope of the compose block?
Update:
This is an issue/feature of the gmail gem - ruby 1.9 blocks have changed but not this much!
In addition to the accepted answer, another workaround is to pass the data in as a method parameter:
def create(trial_email)
...
end
Looks like a GMail issue to me. Inside the blocks, self will be some object from the GMail gem so that you can have to, from, and similar DSL niceties available. You should be able to put self.trial_email into a local variable and then access that inside the blocks:
email_address = self.trial_email
#email = ::Gmail.connect!(gmail_name, gmail_password) do |gmail|
email = gmail.compose do
to 'trial#domain.com'
from email_address
subject email_address
#...
You're expecting (as you're entitled to) that the block should preserve the value of self, as it usually does. It looks like the gmail gem is using instance_exec here which allows it to change the value of self for the block to an instance of Mail::Message (which is why you can call to and from in that block even though you define no such methods)
While instance_exec is handy for producing nice DSLs, it is not without its downsides. Local variable scope isn't affected so you could store either trial_email or self in a local variable prior to the block and then use that local variable inside the block
The problem is that the block you pass to compose method is later passed to Mail.new and finally to Message.new (if I traced the chain correctly) and then this block is evaluated like that here:
instance_eval(&block)
As it's performed inside initialize method of a different object (instance of Message class) you do not have access to attributes of your TrialRequest object.
You can do the same thing without having any troubles like that:
email = gmail.compose
email.to = 'trial#domain.com'
email.from = trial_email
email.subject = trial_email
email.text_part do
content_type 'text/html; charset=UTF-8'
body 'Sign me up.'
end