i am trying to replace some word from a string with gsub function in ruby, but sometimes that works fine and in some cases giving this error? is there any issues with this format
NoMethodError (undefined method `gsub!' for nil:NilClass):
model.rb
class Test < ActiveRecord::Base
NEW = 1
WAY = 2
DELTA = 3
BODY = {
NEW => "replace this ID1",
WAY => "replace this ID2 and ID3",
DELTA => "replace this ID4"
}
end
another_model.rb
class Check < ActiveRecord::Base
Test::BODY[2].gsub!("ID2", self.id).gsub!("ID3", self.name)
end
Ah, I found it! gsub! is a very weird method. Firstly, it replaces the string in place, so it actually modifies your string. Secondly, it returns nil when no substitution has been made. This all sums up to the error you're getting.
The first time you execute that call, it modifies the string assigned to a constant, so it reads as "replace this 3 and name". When you try to run it for a second time, the first gsub will fail to find a string it is looking for so will return nil. The second gsub is then executed on the nil.
On how to solve it - it all depends on what you're trying to achieve. For me, it is somewhat risky to change other class constants (breaks encapsulation). If you just want to get the result without modifying the original string, use gsub (no bang). Or even better, convert those string into a method and use interpolation instead of substitution.
If the strings are just patterns, that should be replaced before get used. A better way would be string Interpolation.
class Test < ActiveRecord::Base
# Here use symbols instead, because symbols themselfs are immutable
# so :way will always equal :way
BODY = {
:new => "replace this %{ID1}",
:way => "replace this %{ID2} and %{ID3}",
:delta => "replace this %{ID4}"
}
end
# HERE you should create another constant based on the
# Test class constants
class Check < ActiveRecord::Base
BODY = {
:way => Test::BODY[:way] % {ID2: self.id, ID3: self.name}
}
# Or you can make it a method
def self.body
Test::BODY[:way] % {ID2: self.id, ID3: self.name}
end
end
this will change every apearance of the hash keys in the string
for example:
str = "%{num1} / %{num1} = 1"
str % {num1: 3} # 3 / 3 = 1
And like #BroiSatse said, you should not change constants of other classes or within the same class itself, at the end they are constants.
Related
I have a Model user with the following method:
def number_with_hyphen
number&.insert(8, "-")
end
When I run it several times in my tests I get the following output:
users(:default).number_with_hyphen
"340909-1234"
(byebug) users(:default).number_with_hyphen
"340909--1234"
(byebug) users(:default).number_with_hyphen
"340909---1234"
(byebug) users(:default).number_with_hyphen
"340909----1234"
It changes the number ?Here are the docs https://apidock.com/ruby/v1_9_3_392/String/insert
When I restructure my method to:
def number_with_hyphen
"#{number}".insert(8, "-") if number
end
If works like expected. The output stays the same!
How would you structure the code, how would you perform the insert?
which method should I use instead. Thanks
If you're using the insert method, which in the documentation explicitly states "modifies str", then you will need to avoid doing this twice, rendering it idempotent, or use another method that doesn't mangle data.
One way is a simple regular expression to extract the components you're interested in, ignoring any dash already present:
def number_with_hyphen
if (m = number.match(/\A(\d{8})\-?(\d+)\z/))
[ m[1], m[2] ].join('-')
else
number
end
end
That ends up being really safe. If modified to accept an argument, you can test this:
number = '123456781234'
number_with_hyphen(number)
# => "12345678-1234"
number
# => "123456781234"
number_with_hyphen(number_with_hyphen(number))
# => "12345678-1234"
number_with_hyphen('1234')
# => "1234"
Calling it twice doesn't mangle anything, and any non-conforming data is sent through as-is.
Do a clone of the string:
"#{number}".clone.insert(8, '-')
I have sample parameter below:
Parameters: {
"utf8"=>"✓",
"authenticity_token"=>"xxxxxxxxxx",
"post" => {
"product_attributes" => {
"name"=>"Ruby",
"product_dtls_attributes" => {
"0"=>{"price"=>"12,333.00"},
"1"=>{"price"=>"111,111.00"}
},
},
"content"=>"Some contents here."
}
Now, the scenario is, I cannot get the price exact value in model.
Instead of:
price = 12,333.00
price = 111,111.00
I get:
price = 12.00
price = 11.00
And now here is what I did in my code:
before_validation(on: :create) do
puts "price = #{self.price}" # I also tried self.price.to_s, but didn't work.
end
UPDATE:
(I am trying do to here is to get the full value and strip the comma).
before_validation(on: :create) do
puts "price = #{self.price.delete(',').to_f}" # I also tried self.price.to_s, but didn't work.
end
Note:
column price is float
The question is, how can I get the exact value of params price.
Thanks!
Looking at the 'price' parameter you provided:
"price"=>"12,333.00"
The problem is with the comma.
For example:
irb(main):003:0> "12,333.00".to_i
=> 12
But you can fix that:
Example:
irb(main):011:0> "12,333.00".tr(",", "_").to_i
=> 12333
The key point is replacing the comma with an underscore. The reason is that 12_333 is the same integer as 12333 (the underscores are ignored). You could just remove the comma with tr(",", "") as well. In this case, you could replace tr with gsub and have the same effect.
By the way, are you aware that your validation method is not doing anything besides printing? Anyway, a before_validation method is not the right approach here because the number will already have been incorrectly converted when the code reaches this point. Instead, you can override the setter on the model:
class MyModel
def price=(new_price)
if new_price.is_a?(String)
new_price = new_price.tr(",", "")
end
super(new_price)
end
end
You can do it like this too:
2.1.1 :002 > "12,333.00".gsub(',', '').to_f
=> 12333.0
This will replace the comma and if you have any decimal value then too it will interpret it:
2.1.1 :003 > "12,333.56".gsub(',', '').to_f
=> 12333.56
The solution I made is to handle it on controller. Iterate the hash then save it. Then it get the proper value which I want to get and save the proper value.
Iterate the following hash and save.
"post" => {
"product_attributes" => {
"name"=>"Ruby",
"product_dtls_attributes" => {
"0"=>{"price"=>"12,333.00"},
"1"=>{"price"=>"111,111.00"}
},
},
"content"=>"Some contents here."
I can't get the full value of price in model because of comma separator. This comma separator and decimal points + decimal places is made by gem.
Price is float, but your data contains a non-numeric character (comma, ","). When the field is converted to a float, parsing likely stops at this character and returns just 12.
I had expected an error to be thrown, though.
I suggest you remove the comma before putting it into the database.
I'm starting to work with Ruby and I have the following module:
module RadioreportHelper
#totalsum = 0
#radio
#daysAndTotals
def load(service, transactionsPerDay)
puts "#{service} : #{transactionsPerDay}"
#radio = service
#daysAndTotals = transactionsPerDay
transactionsPerDay.each{|day, total|
#totalsum += total
}
end
attr_reader :radio, :daysAndTotals, :totalsum
end
I'm running the following unit test case:
class RadioreportHelperTest < ActionView::TestCase
fixtures :services
def test_should_return_populated_radio_module
service = Service.find_by_name("Mix")
transactionsPerDay = {1=>20, 2=>30, 4=>40, 5=>50}
radioReport = RadioreportHelper.load(service, transactionsPerDay)
assert_not_nil(radioReport)
assert_equal("Mix", radioReport.radio.name)
end
end
But I always get the following error:
TypeError: can't convert Service into String
I want the service object to be in the module RadioreportHelper and stored it in the #radio variable not the string.
Thanks, for the all the help guys!
Try adding a to_s method to your Service model.
def to_s
service # or some other method in the model that returns a string
end
It is not necessary to call to_s from inside an interpolated expression, i.e. "#{service}" will return the result of service.to_s.
EDIT
Never mind all of this. Your RadioreportHelper.load method is not being reached -- instead you are getting load from ActiveSupport::Dependencies::Loadable. Try renaming the load method to something else.
(I hate name collisions.)
You should definitely try this:
puts "#{service.to_s} : #{transactionsPerDay}"
Although I am not sure how interpolation for hashes is handled in strings either, so you may need to use
puts "#{service.to_s} : #{transactionsPerDay.to_s}"
I'm trying to remove the commas from a field in a model. I want the user to type a number, i.e. 10,000 and that number should be stored in the database as 10000. I was hoping that I could do some model-side normalization to remove the comma. I don't want to depend on the view or controller to properly format my data.
I tried:
before_validation :normalize
def normalize
self['thenumber'] = self['thenumber'].to_s.gsub(',','')
end
no worky.
http://github.com/mdeering/attribute_normalizer looks like a promising solution to this common problem. Here are a few examples from the home page:
# By default it will strip leading and trailing whitespace
# and set to nil if blank.
normalize_attributes :author, :publisher
# Using one of our predefined normalizers.
normalize_attribute :price, :with => :currency
# You can also define your normalization block inline.
normalize_attribute :title do |value|
value.is_a?(String) ? value.titleize.strip : value
end
So in your case you might do something like this:
normalize_attribute :title do |value|
value.to_s.gsub(',', '')
end
I think you're doing it right. This test passes:
test "should remove commas from thenumber" do
f = Foo.new(:thenumber => "10,000")
f.save
f = Foo.find(f.id)
assert f.thenumber == "10000"
end
And I used your code.
class Foo < ActiveRecord::Base
before_validation :normalize
def normalize
self['thenumber'] = self['thenumber'].to_s.gsub(',','')
end
end
Now, my schema is set up for thenumber to be a string though, not an integer.
Started
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Finished in 0.049666 seconds.
1 tests, 1 assertions, 0 failures, 0 errors
If you wanted to store this in the db as an integer, then you definitely need to override the setter:
def thenumber=(value)
self['thenumber'] = value.to_s.gsub(',','').to_i
end
If you do it your way, with an integer column, it gets truncated by AR....
>> f.thenumber = "10,000"
=> "10,000"
>> f.thenumber
=> 10
That's a little-known thing with Ruby and integers... it auto-casts by truncating anything that's no longer an integer.
irb(main):004:0> i = "155-brian-hogan".to_i
=> 155
Can be cool for things like
/users/155-brian-hogan
#user = User.find_by_id(params[:id])
But not so cool for what you're doing.
So either change the col to a string and use the filter, or change the setter :)
Good luck!
The problem with doing it that way is that for a while, the non-normalized stuff will exist in the object; if you have code that works on the attributes before stuff gets normalised, then that will be a problem.
You could define a setter:
def thenumber=(value)
# normalise stuff here, call write_attribute
end
Unfortunately I think a lot of the Rails form stuff writes the attributes directly, which is one of the reasons I don't tend to use it.
Or you could normalise the params in the controller before you pass them through.
Does ruby let you interchange between a . and [''] ?
I don't know, I'll try later, but I think you are supposed to use .
self.thenumber = self.thenumber.to_s.gsub(',','')
You should return true from your before_validation method, otherwise if the expression being assigned to self['thenumber'] ends up being nil or false, the data will not be saved, per the Rails documention:
If a before_* callback returns false,
all the later callbacks and the
associated action are cancelled.
Ostensibly, you are trying to normalize here then check the result of the normalization with your Rails validations, which will decide if nil/false/blank are okay or not.
before_validation :normalize
def normalize
self['thenumber'] = self['thenumber'].to_s.gsub(',','')
return true
end
I want to define a class method that has access to a local variable. So this would be different for each instance of the class. I know you can make a class method dynamic with lambda like when you use it with named_scope. But can this be done for values that are specific to an instance?
In detail it is the has_attached_file method for the paperclip plugin in rails. I want to pass a lambda for the styles hash so that the image styles can be based off of attributes of the object stored in the DB. Is this possible?
Disclaimer: First, the question (Can you pass self to lambda?) and the problem you're trying to solve (dynamic styles with paperclip) don't fully match up. I won't answer the original question because it's not entirely related to your problem, and rampion took a valiant stab at it.
I'll instead answer your paperclip question.
In detail it is the has_attached_file method for the paperclip plugin in rails. I want to pass a lambda for the styles hash so that the image styles can be based off of attributes of the object stored in the DB. Is this possible?
Yes, it is possible. In paperclip, the :styles option can take a Proc. When the attachment is initialized, if a Proc was used, the attachment itself is passed to the Proc. The attachment has a reference to the associated ActiveRecord object, so you can use that to determine your dynamic styles.
For example, your has_attached_file declaration might look something like this (assuming a User and avatar scenario where the user can customize the size of their avatar):
class User < ActiveRecord::Base
has_attached_file :avatar, :styles => lambda { |attachment|
user = attachment.instance
dimensions = "#{user.avatar_width}x#{user.avatar_height}#"
{ :custom => dimensions }
}
end
Ok, you're being unclear.
Local variables in ruby begin with a lowercase letter (like foo, bar, or steve), and are lexically scoped (like C variables). They have nothing to do with "an instance of a class"
Instance variables in ruby begin with an # sigil (like #foo, #bar, or #carl), and are in scope whenever the current value of self is the object they are stored in.
If you want a method that can access the instance variables of an object directly, that's called an instance method. For example, battle_cry and initialize are both instance methods:
class Character
def initialize(name)
#name=name
end
def battle_cry
#name.upcase + "!!!"
end
def Character.default
new("Leeroy Jenkins")
end
end
A class method, by contrast, is a method for a Class object, and doesn't have access to any of the instance variables of that object. In the above example,
default is a class method.
If you want a (class or instance) method that triggers a change in or gets a value from the current scope, ruby uses a type of callback called a block.
class Character
ATTACKS = [ "Ho!", "Haha!", "Guard!", "Turn!", "Parry!", "Dodge!", "Spin!", "Ha", "THRUST!" ]
def attack
ATTACKS.inject(0) { |dmg, word| dmg + yield(word) }
end
end
person = Character.default
puts person.battle_cry
num_attacks = 0;
damage = person.attack do |saying|
puts saying
num_attacks += 1
rand(3)
end
puts "#{damage} points of damage done in #{num_attacks} attacks"
In the above example, attack uses the yield keyword to call the block passed
to it. When we call attack, then, the local variable num_attacks is still
in scope in the block we pass it (delimited here by do ... end), so we can
increment it. attack is able to pass values into the block, here
they are captured into the saying variable. The block also passes values
back to the method, which show up as the return value of yield.
The word lambda in ruby usually means the lambda keyword, which is used
to make blocks into freestanding, function like objects (which themselves are usually
referred to as lambdas, procs, or Procs).
bounce = lambda { |thing| puts "I'm bouncing a #{thing}" }
bounce["ball"]
bounce["frog"]
So I think what you're asking is whether you can pass a Proc in place of a Hash
for an argument to a method. And the answer is "it depends". If the method only
ever uses the #[] method, then yes:
class Character
attr_accessor :stats
def set_stats(stats)
#stats = stats
end
end
frank = Character.new("Victor Frankenstein")
frank.set_stats({ :str => 7, :dex => 14, :con => 9, :int => 19, :wis => 7, :cha => 11 })
monster = Character.new("Frankenstein's Monster")
monster.set_stats(lambda do |stat_name|
rand(20)
end)
However, it might use some other Hash specific methods, or call the same key multiple times,
which can produce weird results:
monster = Character.new("Frankenstein's Monster")
monster.set_stats(lambda do |stat_name|
rand(20)
end)
monster.stats[:dex] #=> 19
monster.stats[:dex] #=> 1
In which case, you may be better off caching the requests in an intermediate hash. This is fairly easy,
since a Hash can have an initializer block. So if we change the above to:
monster.set_stats(Hash.new do |stats_hash, stat_name|
stats_hash[stat_name] = rand(20)
end)
monster.stats[:dex] #=> 3
monster.stats[:dex] #=> 3
The results are cached in the hash
To see more about Hash block initializers, see ri Hash::new:
-------------------------------------------------------------- Hash::new
Hash.new => hash
Hash.new(obj) => aHash
Hash.new {|hash, key| block } => aHash
------------------------------------------------------------------------
Returns a new, empty hash. If this hash is subsequently accessed
by a key that doesn't correspond to a hash entry, the value
returned depends on the style of new used to create the hash. In
the first form, the access returns nil. If obj is specified, this
single object will be used for all default values. If a block is
specified, it will be called with the hash object and the key, and
should return the default value. It is the block's responsibility
to store the value in the hash if required.
h = Hash.new("Go Fish")
h["a"] = 100
h["b"] = 200
h["a"] #=> 100
h["c"] #=> "Go Fish"
# The following alters the single default object
h["c"].upcase! #=> "GO FISH"
h["d"] #=> "GO FISH"
h.keys #=> ["a", "b"]
# While this creates a new default object each time
h = Hash.new { |hash, key| hash[key] = "Go Fish: #{key}" }
h["c"] #=> "Go Fish: c"
h["c"].upcase! #=> "GO FISH: C"
h["d"] #=> "Go Fish: d"
h.keys #=> ["c", "d"]