learn-co-curriculum / my-collect

My #collect

Objectives

1. Build a method that yields members of a collection to a block.
2. Control the return value of a method that uses yield such that it returns a new collection.

Instructions

You'll be writing your code in lib/my_collect.rb.

You are writing a method that behaves just like the real #collect method. It should take in an argument of a collection, iterate over that collection using a while loop, and execute the code in the block you call it with for each element in the collection (use the yield keyword). It should return the modified collection.

Your #my_collect method, therefore, should not care about the contents of the code block that it is invoked with. For example, let's say we are writing an app to help teachers manage their students. Our teacher has a list of students:

["Tim Jones", "Tom Smith", "Jim Campagno"]

The list includes the first and last name of each student, but our teacher needs to collect a list of just their first names.

So, if our teacher uses #my_collect to collect the first name of his students, it should work like this:

array = ["Tim Jones", "Tom Smith", "Jim Campagno"]
my_collect(array) do |name|
  name.split(" ").first
end

Should return:

["Tim", "Tom", "Jim"]

What if your method was being invoked with a totally different collection and a totally different code block? For example, let's say your #my_collect method is given an argument of a list of programming languages and passed a block that capitalizes the elements yielded to it.

collection = ['ruby', 'javascript', 'python', 'objective-c']
my_collect(collection) do |lang|
  lang.upcase
end

# => ["RUBY", "JAVASCRIPT", "PYTHON", "OBJECTIVE-C"]

Your method should behave the same way––iterating over the given collection and passing each member to the given block––regardless of the content of the collection or the nature of the block.

Make sure to run bundle install before running your tests.

my-collect's Issues

instructions do not match lab

The instructions in the readme file talk about making a method that will take a list of students' full names and return an array of just their first names. However, the lab's spec test file wants you to make a method that will take a list of programming language names in lower case and return an array of the programming language names in upper case.

IDE not working

the IDE is not running code here - other labs still working but doesn't run fully

Consider changing starter code in lib/my_collect.rb

Change:
def my collect()

to:

def my_collect
end

#this way it will not throw a syntax error right away and confuse students.

Glitch

I believe there's a glitch within the last question of the Enumerators Code Challenge quiz (section 7, module 5) When I test 3 out of the 4 answers in ruby, all return true however, my answer was marked wrong. A screenshare coach couldn't give me an answer. Can IT review this and advise?

Thank you

discrepancies in my_collect_spec.rb

I came across a few discrepancies in the spec file that was cloned when i clicked the open button in this exercise. I was given the following spec file:

describe "my_collect" do
  let(:languages) { ['ruby', 'javascript', 'python', 'objective-c'] }
  let(:students) { ['Tim Jones', 'Tom Smith', 'Sophie Johnson', 'Antoin Miller'] }

  it "can handle an empty collection" do
    empty_array = []
    counter = 0
      my_collect(empty_array) do |x|
        counter += 1
      end
    expect(counter).to eq(0)
  end

  it "yields the correct element from a given collection, in this case languages" do
    my_collect(languages) do |language|
      expect(language).to_not eq(nil)
    end
  end

  it "returns a new collection of appropriately modified elements, in this case capitalized languages" do
    expect(my_collect(languages) do |language|
      language.upcase
    end).to eq(["RUBY", "JAVASCRIPT", "PYTHON", "OBJECTIVE-C"])
  end

  it 'does not modify the original collection' do
    my_collect(languages) do |language|
      language.upcase
    end
    expect(languages).to eq(['ruby', 'javascript', 'python', 'objective-c'])
  end

  it "yields the correct element from the given collection, in this case students" do
    my_collect(students) do |student|
      expect(student).to_not eq(nil)
    end
  end

  it "returns a new collection of appropriately modified elements, in this case student first names" do
    expect(my_collect(students) do |language|
      student.split(" ").first
    end).to eq(["Tim", "Tom", "Sophie", "Antoin"])
  end

  it 'does not modify the original collection' do
    my_collect(students) do |language|
      language.upcase
    end
    expect(students).to eq(['Tim Jones', 'Tom Smith', 'Sophie Johnson', 'Antoin Miller'])
  end
end

The solution provided in this exercise's tree does not line up with the spec file that the learn button gave to me.

I also came across an unused variable in the second my_collect(students) block:

it "returns a new collection of appropriately modified elements, in this case student first names" do
    expect(my_collect(students) do |language|
      student.split(" ").first
    end).to eq(["Tim", "Tom", "Sophie", "Antoin"])
  end

This block initially didn't allow my code to pass. I went ahead and changed |language| to |student| on my end which allowed student.split(" ").first to pass.

I'm not sure if this was intentional, but it helped me understand spec files more!

my-collect lab

I seem to be having an issue submitting my lab. I just need help figuring out how to solve this.
Thanks!

errors in rspec file

line 40 passed variable should be student not languages
line 41 string variable should be student not students

Bug in spec file?

Hi Flatiron,

Lines 40 and 41 of my_collect_spec.rb read:

expect(my_collect(students) do |language|
  student.split(" ").first

I think it should be:

expect(my_collect(students) do |student|
  student.split(" ").first

I changed it and it got the test to pass. I hope I didn't just cheat my way through the lesson. haha

Needs explanation of what the Proc is in the tests

my-collect/spec/my_collect_spec.rb

Lines 6 to 10 in cc6b4a5

	saved_block = Proc.new {
	my_collect(empty_array) do |x|
	raise "This block should not run!"
	end
	}

That code is going to confuse the heck out of them. I would just create a counter variable, initialize it to 0 and then increment it in the block. Then expect that the counter is still equal to 0 after running the block.

won't return new arrays, only originals

`keeps returning the original array

def my_collect(array)
i = 0

while i < array.length
yield (array[i])
i = i + 1
end
return array
end

names = ["Tim Jones", "Tom Smith", "Jim Campagno"]
my_collect(names) do |x|
x.split(" ").first

end

collection = ["ruby", "javascript", "python", "objective-c"]
my_collect(collection) do |lang|
lang.upcase

end`

broken Rspec

my-collect-001-prework-web/spec/my_collect_spec.rb on line 40 the block should except student variable instead of language in order to make the test working according to the requirements.

Error in test file

Looks like there's an error in the test file that's causing it to fail even when the method is written correctly. Lines 39 - 43 in my_collect_spec.rb are:

it "returns a new collection of appropriately modified elements, in this case student first names" do
expect(my_collect(students) do |language|
student.split(" ").first
end).to eq(["Tim", "Tom", "Sophie", "Antoin"])
end

Instead of |language| it should be |student| - I made this change and the test passed

error in spec/my_collect_spec.rb

On line 40 of this spec:

expect(my_collect(students) do |language| student.split(" ").first

This creates an unneccessary NameError while testing the code. It should read

expect(my_collect(students) do |student| student.split(" ").first

Thanks,

Brad Watson

my_collect_spec.rb Issue

In the my_collect_spec.rb file, on line 40 (in the "returns a new collection of appropriately modified elements, in this case student first names" section) it says:

expect(my_collect(students) do |language|

I think it should be changed to:

expect(my_collect(students) do |student|

Otherwise "student" is undefined in the rest of the code (lines 41-43):

student.split(" ").first
    end).to eq(["Tim", "Tom", "Sophie", "Antoin"])
  end

clean up readme

remove front matter, added better instructions.

for example they should build this using yield and not .each