Is there a way to make this situation more compact in rails views?
Eg I have haml
= object.count unless object.count ==0
I sort of don't like that has I'm repeating the function there, I would much rather have something like
= object.count unless ==0
Eg if I had more complex statements
= object.relations.where(attribute: "something").count unless zero?
I could split that into two lines say
- cnt = object.relations.where(attribute: "something").count
= cnt unless cnt==0
But for each situation I would have multiple lines, and storing a variable to use once sucks.
EDIT: just to elaborate I want to check if the number is 0, and if so not display anything. It looks nicer in the view that way.
UPDATE:
One of the answers made come up with a solution along these lines
class Object
def unless
self unless yield(self)
end
end
So I can call whatever object I have with a block eg. .unless{|c| c<1}
This lets me tack the conditionals on, and keeps it pretty clear what is going on :), bonus is as it's block driven I can use this on any object :P.
Thanks everyone :)
UPDATE EVEN MORE
Having |c| in the block sucked. So I looked up the api and changed it too
class Object
def unless(&block)
self unless instance_eval(&block)
end
end
So now I can use .count.unless{zero?} to accomplish this :P. Or if I have a complicated condition I can add that in with |c| etc.
If object is an array you can use object.empty? (or object.any? for the reverse case)
Just create a view helper:
def display_count_or_nothing(array)
array.count unless array.count == 0
end
In the view you can use it like this:
<%= display_count_or_nothing(array) %>
i think the following is nice and clear, although i hate the variable "object",
it would be much nicer if the name of the variable described the contents of the array (as plural)
= object.count unless object.empty?
If this is only about count, you can monkey patch Enumerable:
module Enumerable
def count_or_empty_string
self.any? ? self.count : ''
end
end
If object is an enumerable, you can do this:
= object.count_or_empty_string
This will return an "" if object.count == 0 else it will return an integer. So there is no need for unless or if in your HAML anymore.
Related
I commonly need to use this kind of methods where I have to check if an object exists and if this object returns a specific value or a behavior. Is that a better way to write this code?
def set_current_theme
if current_tenant && current_tenant.has_custom_domain?
#theme = Theme.last || Theme.create
end
end
At a first glance, I would just add one conditional: if current_tenant.has_custom_domain? and that should be enough. But the result is generally that there is no such method (in this case has_custom_domain?) for nil class.
Shorter (and i think better) way is to use &. (it's shorthand for try!) like this.
if current_tenant&.has_custom_domain?
#theme = Theme.last || Theme.create
end
What does &. (ampersand dot) mean in Ruby?
I would suggest early return (so called guard clause) instead of :if statement, because you don't have :else clause:
def set_current_theme
return unless current_tenant&.has_custom_domain?
#theme = Theme.last || Theme.create
end
Before I except these two methods I wanted to see if anyone in the community had a better idea to structure these and make the cops pass. The first one with to_s seems a bit crazy too. I was thinking of refactoring the other method but that would be a single line or two.
Thoughts?
Code Examples One:
def destroy(resource_name, id)
delete "#{resource_name.to_s.pluralize}/#{id}"
end
Code Examples Two:
def all_products
products_map = fetch(:products).map { |x| [x['id'], x] }.to_h
variants = fetch :variants
variants.group_by { |x| x['product']['resource']['id'] }.to_a.map do |product_id, product_variants|
product.merge 'variants' => product_variants if product == products_map[product_id]
end.compact
end
For Code example One, maybe this can be used:
delete [resource_name.to_s.pluralize, id].join('/')
For Code example Two, yes you definitely need to refactor it.
Maybe you need to create a separate method that does all the grouping and merging, etc. for the variants part.
I am not sure if this is a good practice, but you can create a private method for it.
Objective: Parse data to display all the id's in the erb file
Problem: NoMethodError in DemoController#index due to this piece of code
#x = obj[i]["id"]
When I replace the "i" in the above piece of code with a number, one id number displays which leads me to believe that the while loop is correct. It just doesn't understand what "i" is.
What am I doing wrong?
Here is my code for my Controller and View
demo_controller.rb
require 'rubygems'
require 'json'
require 'net/http'
require 'httparty'
class DemoController < ApplicationController
respond_to :json
$angelURI = "https://api.angel.co/1/jobs"
def index
response = HTTParty.get('https://api.angel.co/1/jobs/')
obj = JSON.parse(response.body)["jobs"]
arraylength = obj.length
i = 0
while i <= arraylength do
#x = obj[i]["id"]
i += 1
end
end
end
index.html.erb
<%=#x%>
You are assigning a value to the same #x variable at each level of your loop - this will end with #x having the value of the last id - is that the intended behavior ?
I don't see something weird with your array right now, but Ruby tend to favor using each over for:
obj.each do |elem|
#x = elem["id"]
end
Upate: Following zishe good catch about the loop, using each also avoid that kind of question ("do I need to go to the ith element or stop at the ith-1").
By combining best of answers we get:
#x = []
obj.each do |job|
#x << job["id"]
end
i is a counter in while loop, it's basics. I think you looping to more, change <= on < in this:
i = 0
while i < arraylength do
#x = obj[i]["id"]
i += 1
end
Or better do like Martin suggests.
So, you have a off-by-one error: your while loop runs too far (because of the <=). Simple solution: use each (so you do not have to maintain a counter yourself --why make it hard). But on top, I would propose to add a file in lib that will do the parsing of the page.
So, e.g. add a file called lib/jobs_parser.rb that contains something like
require 'httparty'
module JobsParser
ANGEL_JOBS_URI = "https://api.angel.co/1/jobs"
def all_job_ids
all_jobs.map{|j| j["id"]}
end
def all_jobs
response = HTTParty.get(ANGEL_JOBS_URI)
jobs = JSON.parse(response.body)["jobs"]
end
end
What do I do here: the map generates an array containing just the "id" field.
I think it makes more sense, on this level to keep the complete array of jobs or ids.
Note: I drastically shortened the list require statements, most should be auto-required via your Gemfile.
And then in your controller you can write:
class DemoController < ApplicationController
def index
all_job_ids = JobsParser.all_job_ids
#x = all_job_ids.last
end
end
and your view remains the same :)
This has the advantage that you can simply test the JobsParser, through tests, or manually in the rails console, and that your code is a bit more readable.
You have a off-by-one error in your code. Basically, you are looping over the array and are then trying to access one more element than is in the array, which is then returned as nil and naturally doesn't act as a Hash.
Say your obj is an array with 3 elements, thus arraylength is three. You are now fetching 4 elements from the array, the elements with the indexes of 0, 1, 2, and 3. As you only have the 3 elements 0..2, the last one obj[3] doesn't exist.
To keep your existing code, you could change your loop to read as follows:
while i < arraylength do
#...
end
However, to just get the id of the last element in your array, it is much clearer (and much faster) to just use idiomatic ruby and write your whole algorithm as
def index
response = HTTParty.get('https://api.angel.co/1/jobs/')
jobs = JSON.parse(response.body)["jobs"]
#x = jobs.last["id"]
end
I have created a small Ruby class here:
class Star
#Star initialization
def initialize(star, number)
#star = star
#number = number
end
end
and I am looking to initialize a class called Solar System with 100 stars. This is what I have done and it doesn't seem to be working. Any help would be greatly appreciated.
require_relative 'star.rb'
class SolarSystem
#Initialize Game
def initialize(partOfSolarSystem)
#partOfSolarSystem = partOfSolarSystem
#stars_array = []
for i in 0..99
stars_array = Star.new('unknown_star',i)
end
end
def show_solar_system
#code here to show all the initialized stars in solar system
end
end
I can't seem to get it to initialize the array in the constructor. I would then like to be able to print out all of the elements in the stars array. Any help with this would be greatly appreciated.
Also in an effort to eventually move this to a database with rails or something of that nature, should I be looking to hash this or will this be easily converted to mySQL or another DB with some helper functions? I would eventually like to write this into rails and have a dynamic website for it.
Once again, thanks very much.
Your problem is assigning a new value to #stars_array variable on each iteration. There are multiple ways to deal with it:
#stars_array = (0..99).map { |i| Star.new('unknown_star',i) }
By the way, there is a couple of design issues (just for your attention):
Why variable is called stars_array, not just stars?
Why would ever instance of Star class have some object named #star inside? Recursion? :) Seems like #name would be proper and more clear attribute's name.
Don't miss indentation.
EDIT: About DB-mapping. Most common way - inherit both classes from ActiveRecord::Base, and create one-to-many relation from solar system to stars. Each class will have it's own table. Takes absolutely no efforts.
You are assigning the new object every time round the loop. The fix is to append the new object:
#stars_array << Star.new('unknown_star',i)
Or, if you prefer words rather than symbols:
#stars_array.push(Star.new('unknown_star',i))
Or, to be more terse:
100.times {|i| #stars_array << Star.new('unknown_star',i) }
A few things to fix to make it work. In your loop you're assigning a new value to the array rather than appending to it. Secondly, in your loop you're using a local variable stars_array instead of the instance variable #stars_array.
Your initialize method should look like this:
def initialize(part_of_solar_system)
#part_of_solar_system = part_of_solar_system
#stars_array = []
for i in 0..99
#stars_array << Star.new('unknown_star', i)
end
end
Also, you might want to revisit your Ruby idioms, like preferring snake_case to camelCase for variable names and avoiding for loops in favor of each, e.g.
def initialize(part_of_solar_system)
#part_of_solar_system = part_of_solar_system
#stars_array = []
(0..99).each { |i| #stars_array << Star.new('unknown_star', i) }
end
I am developing a Ruby on Rails app. My question is more about Ruby syntax.
I have a model class with a class method self.check:
class Cars < ActiveRecord::Base
...
def self.check(name)
self.all.each do |car|
#if result is true, break out from the each block, and return the car how to...
result = SOME_CONDITION_MEET?(car) #not related with database
end
puts "outside the each block."
end
end
I would like to stop/break out from the each block once the result is true (that's break the each block if car.name is the same as the name parameter once) AND return the car which cause the true result. How to break out in Ruby code?
You can break with the break keyword. For example
[1,2,3].each do |i|
puts i
break
end
will output 1. Or if you want to directly return the value, use return.
Since you updated the question, here the code:
class Car < ActiveRecord::Base
# …
def self.check(name)
self.all.each do |car|
return car if some_condition_met?(car)
end
puts "outside the each block."
end
end
Though you can also use Array#detect or Array#any? for that purpose.
I provide a bad sample code. I am not directly find or check something
from database. I just need a way to break out from the "each" block if
some condition meets once and return that 'car' which cause the true
result.
Then what you need is:
def check(cars, car_name)
cars.detect { |car| car.name == car_name }
end
If you wanted just to know if there was any car with that name then you'd use Enumerable#any?. As a rule of thumb, use Enumerable#each only to do side effects, not perform logic.
you can use include? method.
def self.check(name)
cars.include? name
end
include? returns true if name is present in the cars array else it returns false.
You can use break but what your are trying to do could be done much easier, like this:
def self.check(name)
return false if self.find_by_name(name).nil?
return true
end
This uses the database. You are trying to use Ruby at a place the database can deal with it better.
You can also use break conditional:
break if (car.name == name)
I had to do this exact same thing and I was drawing a blank. So despite this being a very old question, here's my answer:
Note: This answer assumes you don't want to return the item as it exists within the array, but instead do some processing on the item and return the result of that instead. That's how I originally read the question, I realise now that was incorrect - though this approach can be easily modified for that effect (break item insead of break output)
Since returning from blocks is dodgy (nobody likes it, and I think the rules are about to change which makes it even more fraught) this is a much nicer option:
collection.inject(nil) do |_acc, item|
output = expensive_operation(item)
break output if output
end
Note that there are lots of variants; for example, if you don't want an incidental variable, and don't mind starting a second loop in some circumstances, you can invert it like this:
collection.inject(nil) do |acc, item|
break acc if acc
expensive_operation(item)
end