CODEWITHSUNDEEP
ruby
Keith L.
Keith L.

Reputation: 11

Accidental Type conversion in Ruby with strings

I'm trying to solve a challenge where you take in a string of words but return the longest word in the string. My strategy is to break the string into an array of individual words and search the array. However, I'm getting a type conversion error. What is causing the type conversion error? This is particularly strange to me because I don't actually see any type conversion happening here. 

def LongestWord(sen)

  sen1 = sen.split("/\W+/")
  grt = 0
  sen1.each do |i|
      if sen1[i].length > sen1[grt].length # Type conversion error
          grt = i
      end
  end

  sen1[grt] 
end

# keep this function call here    
puts LongestWord(STDIN.gets)

Upvotes: 0

Views: 79

Answers (3)

Derrell Durrett
Derrell Durrett

Reputation: 576

The type conversion is caused by the array entry i being converted (probably unsuccessfully) into an integer (though I suppose it could be ruby trying to convert the array into a hash, and use i as a key to the hash).

Your misunderstanding is that you think you're getting the array's indices passed into the block for each. What is passed in to that block is each individual value in the array. I.e., if your string sen is 'this is a silly string', then the values passed are 'this', 'is', 'a', 'silly', and 'string'.

Upvotes: 2

Edvaldo Silva de Almeida Jr
Edvaldo Silva de Almeida Jr

Reputation: 3723

You don't see the type conversion, but it is there. In more than one place.

As Derrell Durrett pointed out in his answer, your are assuming (wrongly) that the index of the array is passed to the block, not its elements.

Then you write if sen1[i].length > sen1[grt].length. Let's consider the string is 'this is a silly string'. The first element is 'this' and what you are trying to do is if sen1['this'].length > sen1[0].length. As Ruby arrays always have integer indexes, Ruby tries to convert 'this' to an integer in order to find the element at the specified position. Of course this fails!

But your code is not that far from being right. A few small changes and it will run perfectly well:

def longest_word(sen)
  sen1 = sen.split(" ")
  grt = 0
  sen1.each_index do |i|
    if sen1[i].length > sen1[grt].length 
      grt = i
    end
  end
  sen1[grt] 
end

puts LongestWord(STDIN.gets)

Now you'd be passing the indexes with sen1.each_index and it'd be working fine.

Notice that I changed the name of your method to longest_word. This is much better, in fact, because this first capital letter is reserved to constants and class names.

I also would like to point that you are not using a good Ruby style. This could be written like this:

def longest_word(str)
  str.split(" ").max_by{ |s| s.length }
end

and the result would be the same.

Upvotes: 1

the Tin Man
the Tin Man

Reputation: 160551

You get the error because, when the code is running, i is the first value of sen1, which results in sen1['some string'] being evaluated.

An array can't have a string index, only a hash can, resulting in the Type error.

Meditate on this:

def longest_word(sen)

  sen1 = sen.split # => ["foo", "barbaz"]
  grt = 0
  sen1.each do |i|

    i # => "foo"
    sen1 # => ["foo", "barbaz"]
    sen1[i] # => 
    sen1[grt] # => 

    sen1[i].length # => 
    sen1[grt].length # => 

    if sen1[i].length > sen1[grt].length #Type conversion error
      grt = i # => 
    end
  end


  sen1[grt] 

end

# keep this function call here    
longest_word('foo barbaz')

Breaking it down further, here's the offending problem:

sen1 = 'foo barbaz'.split
sen1['foo'] # => 

# ~> TypeError
# ~> no implicit conversion of String into Integer

Upvotes: 1

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