CODEWITHSUNDEEP
ruby
Sam
Sam

Reputation: 3167

What do c == self and yield do?

Can you help me understand what this class does and how we can make use of it?

class Integer
    def myt
        c=0
        until c == self
            yield(c)
            c+=1
        end
        self
    end
end

Thank you.

x = Integer.new
x.myt

I tried to test it but it doesn't work. Error is: "no block given (yield)"

Also, in my book it says to test like this: 5.myt (|| puts "I'm on iteration #{i}! "} but it also gives an error - not sure why or what this line of code means.

Upvotes: 0

Views: 105

Answers (4)

Lorena Nicole
Lorena Nicole

Reputation: 519

Using the example your book gave -- 

5.myt {|i| puts "I'm on iteration #{i}! "} 
#You were missing an object in the pipes and a curly bracket before the pipes (not parentheses)

Allows you to see the internal workings of your myt method. Initializing variable c with a value of 0 the method executes an until look until the condition "c == self" is satisfied. Self references the object, here 5, which the method is acting on.

Therefore ...

def myt
  until c == 5 #Until this is true  
    yield(c) #Do this .. here yield will do whatever the block specified
    c+=1 #Increment on each iteration the value of variable c by 1
  end #closing the until loop
  self #return self 
end

The yield within the method passes control from your method to the parameter, a block, back to the method.

Yield therefore allows you to build methods which can have similar patterns but with block you customize it to do your particular need.

If instead of putting each number maybe all you want to do is put the odd integers between 0 and the integer you call the method on --

5.myt {|i| puts i if i.odd?} # returns I am odd: 1 and I am odd: 3

I would suggest that you write your own blocks here to see how yield works and how you can keep the same method but pass in different blocks and create different method outputs!

Upvotes: 0

grenierm5
grenierm5

Reputation: 186

allonhadaya and PNY did a good job explaining the purpose (enumeration) of the myt method.

Regarding your two questions mentioned in the title:

1.) What does 'c == self' do?

The '==' operator checks whether the integer c and Integer object you instantiate, are equal in value. If they are, the expression evaluates to true.

2.) What does 'yield' do?

The 'yield' statement passes control from the current method to a block which has been provided to the method. Blocks are ruby's implementation of a closure which, simple put, means that a method can be "extended" by calling the method with a block of additional code as long as the method supports a block (ie. incorporates yield statements)

Upvotes: 3

PericlesTheo
PericlesTheo

Reputation: 2469

The method seems to be a times implementation.

Basically 5.times { |i| puts i } and 5.myt { |i| puts i } will do exactly the same thing.

First, it sets a counter to 0, c = 0. Then you have a conditional where it checks if c is equal with self which will always be the integer attached to the method myt. It, then yields the counter and return self when is done.

Upvotes: 2

allonhadaya
allonhadaya

Reputation: 1297

Looks like it enumerates the values between zero inclusively and self exclusively.

allon@ahadaya:~$ irb
irb(main):001:0> class Integer
irb(main):002:1>     def myt
irb(main):003:2>         c=0
irb(main):004:2>         until c == self
irb(main):005:3>             yield(c)
irb(main):006:3>             c+=1
irb(main):007:3>         end
irb(main):008:2>         self
irb(main):009:2>     end
irb(main):010:1> end
=> nil
irb(main):011:0> 5.myt { |i| puts i }
0
1
2
3
4
=> 5
irb(main):012:0>

Upvotes: 2

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