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Ruby Ruby Booleans Build a Simple Todo List Program Part 3: Adding Todo Items

Alessandro Romani
Alessandro Romani
19,723 Points
Posted by Alessandro Romani
Alessandro Romani
19,723 Points

Why do we use todo_item.push() and not @todo_item.push()?

I'm in doubt with instance variable @todo_item. I'm asking how we can push todo_items array in the add_item method if todo_items is local.

Leo Brown
Leo Brown
6,896 Points
Leo Brown
Leo Brown
6,896 Points

This was a while ago for me; can you please post a code sample?

Alessandro Romani
Alessandro Romani
19,723 Points
Alessandro Romani
Alessandro Romani
19,723 Points

This is the code: require "./todo_item"

class TodoList attr_reader :name, :todo_items

def initialize(name) @name = name @todo_items = [] end

def add_item(name) todo_items.push(TodoItem.new(name)) end

def remove_item(name) if index = find_index(name) todo_items.delete_at(index) return true else return false end end

def mark_complete(name) if index = find_index(name) todo_items[index].mark_complete! return true else return false end end

def find_index(name) index = 0 found = false todo_items.each do |todo_item| if todo_item.name == name found = true end if found break else index += 1 end end if found return index else return nil end end end

todo_list = TodoList.new("Groceries") todo_list.add_item("Milk") todo_list.add_item("Eggs") todo_list.add_item("Bread")

if todo_list.remove_item("Eggs") puts "Eggs were removed from the list." end

if todo_list.mark_complete("Milk") puts "Milk was marked as complete." end puts todo_list.inspect

3 Answers

Garrett Carver
Garrett Carver
14,681 Points
Garrett Carver
Garrett Carver
14,681 Points

Hi Alessandro, When you add the line:

attr_reader :name, :todo_items

This allows you to use the variable without putting the @ symbol. Hope this helps. Let me know if you are still confused!

bashburn
bashburn
7,611 Points
bashburn
bashburn
7,611 Points

attr_reader :todo_items creates the method:

def todo_items @todo_items end

Note that this method will return the array @todo_items.

The code in question todo_items.push(), calls the method todo_items which returns the array @todo_items, then the push method adds the new TodoItem object to the array.

Alessandro Romani
Alessandro Romani
19,723 Points
Alessandro Romani
Alessandro Romani
19,723 Points

But with attr_reader can I set the variable todo_item pushing values? If is so what's the difference with attr_writer? Thank you for your help.

Garrett Carver
Garrett Carver
14,681 Points
Garrett Carver
Garrett Carver
14,681 Points

I was not entirely sure about this either, but I found an article that explains it a little better. You can think of your objects as having various attributes. You want your methods to either 'get' or 'set' those attributes. So for example, if you want to set Object.color = "red" then you use attr_writer. On the other hand, if you only want to display the color when interacting with your object, then you would use attr_reader, and return it by calling Object.color. It's all about how you intend your objects to be interacted with when they are called.