Undefined Method When Accessing Hash Element

Undefined method when accessing hash element

Try something like this :

p = {:headline=>"Managing Director at Test company name", :pid=>"0tSsRvCR7r", :first_name=>"John",     :last_name=>"Doe", :industry=>"Financial Services", :summary=>nil,     :public_profile_url=>"http://www.linkedin.com/pub/john-doe/7a/78/606", :distance=>0}
puts p
puts p[:pid]

hash docs

more on hashes

Rails undefined method when accessing hash in view

I edited the form to use a select_tag instead of a c.select element, as follows:

= fields_for :custom_params do |c|
    = label_tag('custom_params[:custom_plot_type]', "Plot Type")
    = select_tag('custom_params[:custom_plot_type]', options_for_select(['Line', 'Scatter', 'Heat Map', 'Column'], @custom_params[:custom_plot_type]))

I still use the value of c for other form elements later on, but using _tag elements instead of elements related to the form builder allow me to use the arbitrary hash within the select tag - thanks @tgmerritt for the suggestion

undefined method `' for {}:Hash

It's because you are trying to assign values for a Hash using << (shovel operator).

Instead, try assigning them like this: (There should be key/value pairs in a Hash)

a = Hash.new
a[:foo] = "Bom dia!"

or,

a = {foo: "Bom dia!"}

Ruby hash error: undefined method [] when attempting to set deeply nested keys

Hashes aren't nested by default. As my_hash[first_key] is not set to anything, it is nil. And nil is not a hash, so trying to access one of its elements fails.

So:

my_hash = {}
first_key = 1
second_key = 2
third_key = 3

my_hash[first_key] # nil
my_hash[first_key][second_key]
# undefined method `[]' for nil:NilClass (NoMethodError)

my_hash[first_key] = {}
my_hash[first_key][second_key] # nil

my_hash[first_key][second_key] = {}

my_hash[first_key][second_key][third_key] = 100
my_hash[first_key][second_key][third_key] # 100

Ruby - NoMethodError: undefined method for hash

you can access the value like this

availability_zone_id  = $evm.root.attributes["dialog_param_placement_availability_zone"]

Here are some great answers explaining how you can access hash values.

Getting undefined method `[]=' for nil:NilClass error when injecting array with hash

Since puts is the last statement in the block and it returns nil, nil is returned causing the accumulator hash to be nil in the second iteration. You should return the hash. And you should pass the array as an argument to the inj_hash method to make it reusable.

def inj_hash(arr)
  arr.inject({}) do |hash, element|
    hash[element.first] = element.last
    hash
  end
end

inj_hash([[:key1, "value1"], [:key2, "value2"]])
#=> {:key1=>"value1", :key2=>"value2"}

The simplest solution to create a hash from an array of key-value pairs is to use Hash::[].

arr = [[:key1, "value1"], [:key2, "value2"]]
Hash[arr]
#=> {:key1=>"value1", :key2=>"value2"}

Ruby undefined method for hash

Hash does not have an add method (see here). It does have store which requires a key & value pair so your code might read:

if schemes.has_key?(schemeName)
   puts "This scheme has already been added "
else
   schemes.store(schemeName, scheme)
end

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