Help on this Method

Ruby
#1

class Hello
def self.best_sentence(sentences,desired_words)
ranked_sentences = sentences.sort_by do |s|
s.words.length - (s.downcase.words - desired_words).length
end
ranked_sentences.last
end

def words
scan(/\w[\w’-]*/)
end

end

puts Hello.best_sentence("[This is a test, This is a ruby
test]",%q{ruby test})

The error always prompting me an undefined method `sort_by’ for “[This
is a test, This is a ruby test]”:String (NoMethodError)

#2

Hello Suresh,

this is because Array#sort_by is undefined. Which means there is no
method sort_by in the Array class. You can check this by looking at the
documentation for Array:

https://ruby-doc.org/core-2.3.0/Array.html#method-i-sort_by

There is however, a method Array#sort_by! (The exclamation mark is
important.) The exclamation mark means (by convention) that a method
changes the state of the object, which is another way of saying that it
changes the values of (at least) one of the object’s variables.

#3

B. Onzo wrote in post #1185125:

Joe Gain wrote in post #1185124:

Hello Suresh,

this is because Array#sort_by is undefined. Which means there is no
method sort_by in the Array class. You can check this by looking at the
documentation for Array:

https://ruby-doc.org/core-2.3.0/Array.html#method-i-sort_by

There is however, a method Array#sort_by! (The exclamation mark is
important.) The exclamation mark means (by convention) that a method
changes the state of the object, which is another way of saying that it
changes the values of (at least) one of the object’s variables.

sort_by comes from Enumerable, but that has nothing to do
with the problem at hand.

The problem is actually given in the error message:

undefined method `sort_by’ for “[This is a test, This is a ruby
test]”:String (NoMethodError)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Sorry, wanted to underline the pertinent part:

“[This is a test, This is a ruby test]”:String

#4

The problem is still the same when i tried to
1.include Enumerable
2.sort_by!
3.sort!
4.sort

#5

Joe Gain wrote in post #1185124:

Hello Suresh,

this is because Array#sort_by is undefined. Which means there is no
method sort_by in the Array class. You can check this by looking at the
documentation for Array:

https://ruby-doc.org/core-2.3.0/Array.html#method-i-sort_by

There is however, a method Array#sort_by! (The exclamation mark is
important.) The exclamation mark means (by convention) that a method
changes the state of the object, which is another way of saying that it
changes the values of (at least) one of the object’s variables.

sort_by comes from Enumerable, but that has nothing to do
with the problem at hand.

The problem is actually given in the error message:

undefined method `sort_by’ for “[This is a test, This is a ruby
test]”:String (NoMethodError)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

#6

B. Onzo is totally right! My bad. Here was I thinking you need to read
the Error message?! :smiley:

(Actually, I was a bit distracted by what was going on in the block,
calling Hello#word all the time.)

The syntax error is due to you trying to call an Array method on a
String object.

This is an Array of String(s):

sentences = []
sentences[0] = “I like ruby”
sentences[1] = “You like ruby”
sentences[2] = “We all like ruby”

Or, more commonly

more_sentences = [ “This that and”, “the other” ]

So, now you have your Array and you can use all the Array methods to do
stuff with the “sentences” (which are Strings).

#7

Joe Gain wrote in post #1185128:

B. Onzo is totally right! My bad. Here was I thinking you need to read
the Error message?! :smiley:

(Actually, I was a bit distracted by what was going on in the block,
calling Hello#word all the time.)

The syntax error is due to you trying to call an Array method on a
String object.

This is an Array of String(s):

sentences = []
sentences[0] = “I like ruby”
sentences[1] = “You like ruby”
sentences[2] = “We all like ruby”

Or, more commonly

more_sentences = [ “This that and”, “the other” ]

So, now you have your Array and you can use all the Array methods to do
stuff with the “sentences” (which are Strings).

now they are saying this
undefined method `words’ for “I like ruby”:String (NoMethodError)

which i place the method words inside the Hello class

#8

undefined method `words’ for “I like ruby”:String (NoMethodError)
which i place the method words inside the Hello class

Well - if the method words() resides in class Hello, then it is
not available on class String.

You need to make sure to call .words() only on objects of class
Hello then - have a look why you have a String object when you
instead expect a Hello object.