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Ruby Build a Todo List Application with Rails 4 Build a Todo List Application with Rails 4 Creating Methods in Tests

Posted by Andrew Stelmach
Andrew Stelmach
12,583 Points

Don't understand why this code works

def create_todo_list(options={})
        options[:title] ||= "My todo list" #means if we don't send in a title, it will be "My todo list". If we do send one in, it'll be that.
        options[:description] ||= "This is my todo list."

        visit "/todo_lists"
        click_link "New Todo list"
        expect(page).to have_content("New todo_list")

        fill_in "Title", with: options[:title]
        fill_in "Description", with: options[:description]
        click_button "Create Todo list"
    end

    it "redirects to the todo list index page on success" do
        create_todo_list
        expect(page).to have_content("My todo list")
    end

    it "displays an error when the todo list has no title" do
        create_todo_list(title: "")
        expect(page).to have_content("error")
        expect(TodoList.count).to eq(0)

        visit "/todo_lists"
        expect(page).to_not have_content("This is what I'm doing today.")
    end

Here's how I understand it: on the first line, the create_todo_list takes one argument, called 'options'. If no argument is sent in to the method, the argument 'options' becomes an empty hash by default.

Let's say we run simply create_todo_list. A key called :title is created in the hash, and its value is "My todo list". Another key, :description, is created, and is given a value of "This is my todo list."

I get that, and how the rest of the method runs after that.

Now, here, we run: create_todo_list(title: "")

I don't get why this works. I would have thought the argument needs to be like this: create_todo_list({:title => ""})

But this doesn't work.

Don't we need to create a hash with a key of :title and a value of "", for the argument, in order for the method to work?

How does title: "" create a hash with a key of :title and a value of ""?

mikescs
mikescs
5,018 Points

It's a shorthand you can use key: 'value'

This helps : http://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Literals

Andrew Stelmach
Andrew Stelmach
12,583 Points

That ALMOST hits the spot, Mike. Solid link, thanks!

However, in that wikibook they say that:

hash = { symbol: 1 }
# => { :symbol => 1 }

But in my code it's run inside an argument with no curly braces:

create_todo_list(title: "")

So, is it simply the case that this means:

create_todo_list( { :title => "" } )

?

EDIT: well, I should have done this before....! I played around with a little test file and:

def method(options)
    puts options
end

method(title: "value")

=> {:title => "value"}

So, there's our answer. It's simply shorthand, BUT I WISH THEY'D TOLD ME THAT IN THE TUTORIAL!!

I know too much handholding is a bad thing, but in the Ruby tutorials in Treehouse, I've found that they fail to explain little things like this that are so confusing for a beginner.

I even completed the entire Ruby Foundations (or whatever it was called) - it was a beast, and they didn't cover shorthand like this. And shorthand like this is REALLY REALLY common in Rails.

Come on, Treehouse, where do you cover shorthand in your tutorials?

2 Answers

Andrew Stelmach
Andrew Stelmach
12,583 Points

I made a blog post about this here: http://rubywarriors.com/2014/12/05/shorthand-way-to-pass-a-hash-into-a-method-as-an-argument-symbols-for-keys/

(this may be a shameless plug, but it IS a good summary of the above!)

Codye Watson
Codye Watson
16,835 Points
Codye Watson
Codye Watson
16,835 Points

This was taught in Ruby Foundations.

http://teamtreehouse.com/library/ruby-foundations/ruby-core/symbols

@1:55