Ruby error - Undefined Method - ruby-on-rails

Question

I am try to write a function that will find the items in an array which match the string passed to the function. See code below.
class Island
def filter(string)
for element in self
if element.include? (string)
yield(element)
end
end
end
end
list = ["sasha","rory","rob","anthony","andre","tariq","kimberly","antoinette"]
list.filter("an"){|i| puts i}</i>
How i keep getting "undefined method 'filer' for #
I'm not sure what i'm doing wrong.

Answer 1

First let me object against the solution posted by #Sravan :
While it is true - and sometimes even a good solution - to monkey-patch a class, you have to be careful how to do it, because it may become a time bomb:
Ruby evolves, and new versions often add methods to existing classes. This means that if you add a method Array#search, and a new version of Ruby will also add a method of the same name, your new method will SILENTLY override the one in Ruby. You likely won't notice it for long time, until you are using a feature which is supposed to use Rubys Array#search - maybe by using something new in stdlib - and you get weird results. To track down this type of error can be a nightmare. This is exactly the case when you use search as a method name.
Now, how to do it then? Three possibilities:
(1) If you monkey-patch, use at least a method name which is unlikely to become part of the official interface. It might have your project's name as a prefix, or plenty of underscore characters, and so on. Note that this is not 100% foolproof: A later version of Ruby might add under the hood a private method with exactly the same name than the one you were choosing, but of course the odder your name, the less likely this will happen.
(2) If you don't like this idea of using "clumsy" names, you could at least test before defining the new method, whether it already exists, and throw an exception if it doesn't:
class Array
if self.method_defined?(:search)
raise "#{self.class}::search already defined"
else
def search(...)
...
end
end
end
(3) The third possibility is to avoid monkey-patching and keep the method in your Island class. In this case, the method definition would be different:
class Island
def self.filter(array, string)
...
end
end
and it would be called by
Island.filter(myarray, mystring)
UPDATE: Forgot a forth possibility:
(4) You can make Island a subclass of Array. I don't know what else you want to do with your islands, but maybe this is an option worth considering:
class Island < Array
def filter(string)
...
end
end
Of course, when invoking filter, you need to turn your array into an island, before you can use it:
list = Island.new([....])

Answer 2

Following ruby's convention over configuration, you can add/overwrite any method in any class
So, adding a function to array class makes it accessible to all the arrays. So, in this solution.
1) First thing is you have taken the filter function in Island class, instead, you need to take inside Array class since the list is an array.
class Array
def filter(string)
for element in self
if element.include? (string)
yield(element)
end
end
end
end
list = ["sasha","rory","rob","anthony","andre","tariq","kimberly","antoinette"]
list.filter("an"){|i| puts i}
O/P:
anthony
andre
antoinette
2) Since Filter is a keyword as suggested by other answer, take another name for it. Eg: search
class Array
def search(string)
for element in self
if element.include? (string)
yield(element)
end
end
end
end
list.search("an"){|i| puts i}