TypeError: no implicit conversion of Symbol into Integer

I encounter a strange problem when trying to alter values from a Hash. I have the following setup:

myHash = {
  company_name:"MyCompany", 
  street:"Mainstreet", 
  postcode:"1234", 
  city:"MyCity", 
  free_seats:"3"
}

def cleanup string
  string.titleize
end

def format
  output = Hash.new
  myHash.each do |item|
    item[:company_name] = cleanup(item[:company_name])
    item[:street] = cleanup(item[:street])
    output << item
  end
end

When I execute this code I get: "TypeError: no implicit conversion of Symbol into Integer" although the output of item[:company_name] is the expected string. What am I doing wrong?

Your item variable holds Array instance (in [hash_key, hash_value] format), so it doesn't expect Symbol in [] method.

This is how you could do it using Hash#each:

def format(hash)
  output = Hash.new
  hash.each do |key, value|
    output[key] = cleanup(value)
  end
  output
end

or, without this:

def format(hash)
  output = hash.dup
  output[:company_name] = cleanup(output[:company_name])
  output[:street] = cleanup(output[:street])
  output
end

This error shows up when you are treating an array or string as a Hash. In this line myHash.each do |item| you are assigning item to a two-element array [key, value], so item[:symbol] throws an error.

You probably meant this:

require 'active_support/core_ext' # for titleize

myHash = {company_name:"MyCompany", street:"Mainstreet", postcode:"1234", city:"MyCity", free_seats:"3"}

def cleanup string
  string.titleize
end

def format(hash)
  output = {}
  output[:company_name] = cleanup(hash[:company_name])
  output[:street] = cleanup(hash[:street])
  output
end

format(myHash) # => {:company_name=>"My Company", :street=>"Mainstreet"}

Please read documentation on Hash#each

myHash.each{|item|..} is returning you array object for item iterative variable like the following :--

[:company_name, "MyCompany"]
[:street, "Mainstreet"]
[:postcode, "1234"]
[:city, "MyCity"]
[:free_seats, "3"]

You should do this:--

def format
  output = Hash.new
  myHash.each do |k, v|
    output[k] = cleanup(v)
  end
  output
end

Ive come across this many times in my work, an easy work around that I found is to ask if the array element is a Hash by class.

if i.class == Hash

    notation like i[:label] will work in this block and not throw that error

end