I'm trying to multiple[sic] parameters to a hash and getting this error:
`method': wrong number of arguments (3 for 0) (ArgumentError)
Could someone tell me how I could accomplish this/what I am doing wrong?
class MyClass
attr_accessor :variable
def initialize
#variable = {}
end
def method(**parameter)
parameter.each {|k,v| #variable[k] = v}
end
end
new_class = MyClass.new
p new_class.method(["key", 1],["house", 2],["key", 3])
You might want to consider more idiomatic use of Ruby
class MyClass
def initialize
#variable = {}
end
def method hash
#variable.merge! hash
end
end
Then use it like this
foo = MyClass.new
foo.method a: 1, b: 2
The last line is sugared-up Ruby for
foo.method({:a => 1, :b => 2})
Hash#merge! docs
Related
I have the following code where I set attr_reader and attr_writer manually.
class Pairs
attr_reader :pair, :asks, :bids, :isFrozen, :seq, :main_currency, :sub_currency
attr_writer :pair, :asks, :bids, :isFrozen, :seq
def initialize (key, args)
#pair = key
#main_currency, #sub_currency = key.split('_')
args.each {|k,v|
if numeric?(v) then v=v.to_f end
self.instance_variable_set("##{k}".to_sym, v)
}
end
private
def numeric?(string)
Float(string) != nil rescue false
end
end
Is there a way to automatically set them based on the keys of the arguments, like I'm automatically filling #k with v? Can I set attr_reader for each #k?
I suppose something like:
self.attr_reader("##{k}")
or even better for all objects of the class, something like:
Pairs << attr_reader("##{k}")
I am going to assume that you may be creating this with many keys specific to different Hash if this is the case then rather than clutter the individual instances with unneeded readers for non existent keys let's use the singleton_class for this.
So your final Pairs class could look something like
class Pairs
attr_reader :main_currency, :sub_currency
attr_accessor :pair, :asks, :bids, :isFrozen, :seq
def initialize (key, args)
#pair = key
#main_currency, #sub_currency = key.split('_')
args.each do |k,v|
singleton_class.send(:attr_reader,k)
instance_variable_set("##{k}", convert_numeric(v))
end
# Alternatively:
# args.each do |k,v|
# val = convert_numeric(v)
# define_singleton_method(k) {val}
# end
end
private
def convert_numeric(val)
Float(Rational(val)) rescue val
end
end
TL;DR
For Example: (using #mudasobwa's approach)
class C
def extend_self_with_reader name
self.class.send :attr_reader, name
end
def initialize *keys
keys.each(&method(:extend_self_with_reader))
end
end
This causes subsequent readers to clutter the instance and bleed across instances:
a = C.new(:a,:b)
a.a #=> nil
b = C.new
b.a #=> nil
c = C.new(:r)
c.a #=> nil
c.r #=> nil
a.methods.sort - Object.methods
#=> [:a, :b, :extend_self_with_reader, :r]
a.r #=> nil (hmmmmm)
Instead localize these readers buy using the singleton_class of the instance like:
class C
def initialize *keys
singleton_class.send(:attr_reader, *keys)
end
end
Then
a = C.new(:a,:b)
a.a #=> nil
b = C.new
b.a #=> NoMethodError: undefined method `a'
c = C.new(:r)
c.a #=> NoMethodError: undefined method `a'
c.r #=> nil
a.r #=> NoMethodError: undefined method `r'
a.methods.sort - Object.methods
#=> [:a,:b]
b.methods.sort - Object.methods
#=> []
Using the singleton_class localizes these readers to the instance of the object rather than bleeding them into the Class definition. If attr_reader is not a requirement then this would also be sufficient:
keys.each {|k| define_singleton_method(k) {}}
I doubt I understood the question, but from what I get you want to dynamically extend your class with attribute readers at runtime.
This method would do:
def extend_self_with_reader name
self.class.send :attr_reader, name
end
Test:
class C
def extend_self_with_reader name
self.class.send :attr_reader, name
end
def initialize *keys
puts keys.inspect
keys.each(&method(:extend_self_with_reader))
end
end
cc = C.new(*%i|a b c|)
cc.a #⇒ nil
Perhaps look into define_method.
I'm not 100% sure that I understand the problem, but check this out:
hash = { a: 1, b: 2, c: 3 }
hash.keys.each do |key|
define_method(key) do
hash[key]
end
end
There are now methods for a, b, and c:
a => 1
b => 2
c => 3
That essentially makes an attr_reader for all the keys in the hash. You could do something similar for an attr_writer.
How can I call a nested hash of methods names on an object?
For example, given the following hash:
hash = {:a => {:b => {:c => :d}}}
I would like to create a method that, given the above hash, does the equivalent of the following:
object.send(:a).send(:b).send(:c).send(:d)
The idea is that I need to get a specific attribute from an unknown association (unknown to this method, but known to the programmer).
I would like to be able to specify a method chain to retrieve that attribute in the form of a nested hash. For example:
hash = {:manufacturer => {:addresses => {:first => :postal_code}}}
car.execute_method_hash(hash)
=> 90210
I'd use an array instead of a hash, because a hash allows inconsistencies (what if there is more than one key in a (sub)hash?).
object = Thing.new
object.call_methods [:a, :b, :c, :d]
Using an array, the following works:
# This is just a dummy class to allow introspection into what's happening
# Every method call returns self and puts the methods name.
class Thing
def method_missing(m, *args, &block)
puts m
self
end
end
# extend Object to introduce the call_methods method
class Object
def call_methods(methods)
methods.inject(self) do |obj, method|
obj.send method
end
end
end
Within call_methods we use inject in the array of symbols, so that we send every symbol to the result of the method execution that was returned by the previous method send. The result of the last send is automatically returned by inject.
There's a much simpler way.
class Object
def your_method
attributes = %w(thingy another.sub_thingy such.attribute.many.method.wow)
object = Object.find(...)
all_the_things << attributes.map{ |attr| object.send_chain(attr.split('.')) }
end
def send_chain(methods)
methods.inject(self, :try)
end
end
There is no predefined method, but you can define your own method for that:
class Object
def send_chain(chain)
k = chain.keys.first
v = chain.fetch(k)
r = send(k)
if v.kind_of?(Hash)
r.send_chain(v)
else
r.send(v)
end
end
end
class A
def a
B.new
end
end
class B
def b
C.new
end
end
class C
def c
D.new
end
end
class D
def d
12345
end
end
chain = { a: { b: { c: :d } } }
a = A.new
puts a.send_chain(chain) # 12345
Tested with http://ideone.com/mQpQmp
I have the following class:
class Alphabet
attr_reader :letter_freqs, :statistic_letter
def initialize(lang)
#lang = lang
case lang
when :en
#alphabet = ('A'..'Z').to_a
#letter_freqs = { ... }
when :ru
#alphabet = ('А'..'Я').to_a.insert(6, 'Ё')
#letter_freqs = { ... }
...
end
#statistic_letter = #letter_freqs.max_by { |k, v| v }[0]
end
end
foo = Alphabet.new(:en)
The central member here is #alphabet.
I'd like to make it some sort of a container class to invoke Array methods directly like
foo[i]
foo.include?
instead of explicitly accessing #alphabet:
foo.alphabet[i]
foo.alphabet.include?
I know I could define a lot of methods like
def [](i)
#alphabet[i]
end
but I'm looking for a proper way of "inheriting" them.
You can use Forwardable (it is included in the Ruby standard library):
require 'forwardable'
class Alphabet
extend Forwardable
def_delegators :#alphabet, :[], :include?
def initialize
#alphabet = ('A'..'Z').to_a
end
end
foo = Alphabet.new
p foo[0] #=> "A"
p foo.include? 'ç' #=> false
If you wish to delegate all the methods not defined by your class you can use SimpleDelegator (also in the standard library); it lets you delegate all the methods that are not responded by the instance to an object specified by __setobj__:
require 'delegate'
class Alphabet < SimpleDelegator
def initialize
#alphabet = ('A'..'Z').to_a
__setobj__(#alphabet)
end
def index
'This is not #alphabet.index'
end
end
foo = Alphabet.new
p foo[0] #=> "A"
p foo.include? 'ç' #=> false
p foo.index #=> "This is not #alphabet.index"
When the delegate doesn't need to be dynamic you can arrange the master class to be a subclass of DelegateClass, passing the name of the class to be delegated as argument and calling super passing the object to be delegated in the #initialize method of the master class:
class Alphabet < DelegateClass(Array)
def initialize
#alphabet = ('A'..'Z').to_a
super(#alphabet)
end
More info about the delegation design pattern in Ruby here
You could extend the Forwardable module:
class Alphabet
require 'forwardable'
extend Forwardable
attr_accessor :alphabet
def initialize
#alphabet = [1,2,3]
end
def_delegator :#alphabet, :[], :include?
end
Then you can do:
alpha = Alphabet.new
alpha[1]==hey.alphabet[1]
=> true
Warning:
Don't try to delegate all methods (don't know if that's even possible) since they probably share some of the same method names such as class, which would probably make chaos.
In Ruby you can extend Objects like this.
class Array
def second
self[1]
end
end
[1, 2, 3, 4, 5].second
# => 2
Or if you want to inherit an Array.
class Foo < Array
def second
self[1]
end
end
[1, 2, 3, 4, 5].include? 2
# => true
[1, 2, 3, 4, 5].second
# => 2
If you have any further questions, comment and I will update the answer.
For academic reasons, I'd like to make an instance of Ruby class act like a hash.
GOALS
Initialize MyClass instance with a hash # success
Request values from instance of myClass, like a hash # success
Then set properties as a hash # fail
Although some discussion exists, I tried what's out there (1, 2) with no success. Let me know what I'm doing wrong. Thanks!
class MyClass
attr_accessor :my_hash
def initialize(hash={})
#my_hash = hash
end
def [](key)
my_hash[key]
end
def set_prop(key, value)
myhash[key] = value
end
end
test = myClass.new({:a => 3}) #=> #<MyClass:0x007f96ca943898 #my_hash={:a=>3}>
test[:a] #=> 3
test[:b] = 4 #=> NameError: undefined local variable or method `myhash' for #<MyClass:0x007f96ca9d0ef0 #my_hash={:a=>3}>
You declared set_prop, but you're using []= in tests. Did you mean to get this?
class MyClass
attr_accessor :my_hash
def initialize(hash={})
#my_hash = hash
end
def [](key)
my_hash[key]
end
def []=(key, value)
my_hash[key] = value
end
end
test = MyClass.new({:a => 3}) # success
test[:a] # success
test[:b] = 4 # success
test.my_hash # => {:a=>3, :b=>4}
module HashizeModel
def [](key)
sym_key = to_sym_key(key)
self.instance_variable_get(sym_key)
end
def []=(key, value)
sym_key = to_sym_key(key)
self.instance_variable_set(sym_key, value)
end
private
def to_sym_key(key)
if key.is_a? Symbol
return ('#'+key.to_s).to_sym
else
return ('#'+key.to_s.delete('#')).to_sym
end
end
end
You should write it as test = MyClass.new({:a => 3}) and the below code should work.
class MyClass
attr_accessor :my_hash
def initialize(hash={})
#my_hash = hash
end
def [](key)
#my_hash[key]
end
def []=(key,val)
#my_hash[key]=val
end
def set_prop(key, value)
#myhash[key] = value
end
end
test = MyClass.new({:a => 3})
test[:a]
test[:b]= 4
test.my_hash # => {:a=>3, :b=>4}
I have a class like:
class Configuration
def self.files
##files ||= Array.new
end
end
Now instead of doing this:
irb(main):001:0> Configuration.files
=> [file, file, file]
I would like to be able to do this:
irb(main):001:0> Configuration
=> [file, file, file]
But I can't figure out how, any ideas?
#glenn jackman:
I was thinking of adding extra methods to a 'Configuration' constant that's a hash. So if I had...
Configuration = Hash.new
Configuration[:foo] = 'bar'
I wanted to be able to save this Configuration hash constant to be able to dump to and load from a YAML file I wanted to be able to use...
Configuration.load
Configuration.save
I wanted the Configuration class to look like
class Configuration
def self.save
open('config.yml', 'w') {|f| YAML.dump( self , f)}
end
def self.load
open('config.yml') {|f| YAML.load(f)}
end
end
You could possibly get the effect you are looking for by adding a method to the top level object which implicitly calls Configuration.files, but you can't really make a reference to a class invoke a method on it. You can alias the method to something shorter, but you will need to call something.
irb's top level just calls 'inspect' on the result, so by overriding it you can customize what you see in irb:
$ irb
>> class Configuration
>> def self.files
>> ##files ||= Array.new
>> end
>> def self.inspect
>> ##files.inspect
>> end
>> end
=> nil
>> Configuration.files << 1 << 2 << 3
=> [1, 2, 3]
>> Configuration
=> [1, 2, 3]
You could do something like this:
class Configuration
(class << self; self; end).module_eval do
def files
['foo','bar','baz']
end
def to_s
files
end
end
end
This would define the Configuration.files method and say that the to string conversion would return the result of that method. But I am really not sure why you would want to do this. It seems quite wrong.
wpc#wpc-laptop:~$ irb
irb(main):001:0> 'a'
=> a
irb(main):002:0> def A
irb(main):003:1> end
=> nil
irb(main):004:0> A
NameError: uninitialized constant A
from (irb):4
from :0
irb(main):005:0> class A
irb(main):006:1> end
=> nil
irb(main):007:0> A
=> A
irb(main):008:0> class A
irb(main):009:1> (class ['g']
irb(main):012:3> end
irb(main):013:2> def to_s
irb(main):014:3> g
irb(main):015:3> end
irb(main):016:2> end
irb(main):017:1> end
=> nil
irb(main):018:0> A
=> g
irb(main):019:0> class B
irb(main):020:1> class def to_s
irb(main):022:3> 'g'
irb(main):023:3> end
irb(main):024:2> end
irb(main):025:1> end
=> nil
irb(main):026:0> B
=> g
irb(main):027:0> class B
irb(main):028:1> class def files
irb(main):030:3> ['a','b','c']
irb(main):031:3> end
irb(main):032:2> def to_s
irb(main):033:3> files
irb(main):034:3> end
irb(main):035:2> end
irb(main):036:1> end
=> nil
irb(main):037:0> B
=> abc
The right solution is to using the class' method of to_s, but what it return is only the string; and then you can set the inspect for using. See the follows' detail for help.
class A
class<<self
def to_s
......
end
end
end