Learning Exercise
OpenStruct allows you to easily create an object from a Hash.
Rather than having to access using Hash keys, OpenStruct instead allows us to use methods to access and set values.
attributes = { name: "Jeremy Walker", age: 21, location: "Nomadic" }
person = OpenStruct.new(attributes)
person.name
#=> Jeremy Walker
person.location
#=> Nomadic
#Â Update the age
person.age = 35
# It sets correctly
person.age
#=> 35
One bonus to this approach is that we can take advantage of a shortcut when using block syntax.
In situations where a block calls a single method, you can replace the block with &: followed by the method name.
For example, these two lines are synonymous:
people.sum { |person| person.age }
people.sum(&:age)
All of the classes you've seen in previous exercises have been part of Ruby's Core Library.
OpenStruct is part of Ruby's Standard Library (often shortened to "stdlib") - a collection of classes for working with things such as dates, json, and networking. It also provides some useful functionality for making your code easier to work with.
When using classes that are not from the Core Library — your own code in different files, classes from stdlib, or external dependencies — we need to import them using the require method before we can use them.
For example:
require 'ostruct'
person = OpenStruct.new(name: "Jeremy Walker")
# ...
You're continuing to work on the stock management system you built previously. Since discovering OpenStruct and block shortcuts, you've decided to refactor the code a little. Rather than storing the items as hashes, you're going to utilize your newfound skills.
You want to continue to retrieve the list of items in stock, but this time they should be objects that can have methods called on them.
inventory = BoutiqueInventory.new([
{price: 65.00, name: "Maxi Brown Dress", quantity_by_size: {s: 3, m: 7, l: 8, xl: 4}},
{price: 50.00, name: "Red Short Skirt", quantity_by_size: {}},
{price: 29.99, name: "Black Short Skirt", quantity_by_size: {s: 1, xl: 4}},
{price: 20.00, name: "Bamboo Socks Cats", quantity_by_size: {s: 7, m: 2}}
])
inventory.items.first.name
# => "Maxi Brown Dress"
inventory.items.first.price
# => 65
inventory.items.size
# => 4
Refactor item_names to use the new block shortcut you've learnt rather than hashes.
As a reminder, the method should return:
BoutiqueInventory.new([
{price: 65.00, name: "Maxi Brown Dress", quantity_by_size: {s: 3, m: 7, l: 8, xl: 4}},
{price: 50.00, name: "Red Short Skirt", quantity_by_size: {}},
{price: 29.99, name: "Black Short Skirt", quantity_by_size: {s: 1, xl: 4}},
{price: 20.00, name: "Bamboo Socks Cats", quantity_by_size: {s: 7, m: 2}}
]).item_names
# => ["Bamboo Socks Cats", "Black Short Skirt", "Maxi Brown Dress", "Red Short Skirt"]
Refactor total_stock to use the openstruct's method, rather than referencing a hash.
As a reminder, the method should return::
BoutiqueInventory.new([
{price: 65.00, name: "Maxi Brown Dress", quantity_by_size: {s: 3, m: 7, l: 8, xl: 4}},
{price: 50.00, name: "Red Short Skirt", quantity_by_size: {}},
{price: 29.99, name: "Black Short Skirt", quantity_by_size: {s: 1, xl: 4}},
{price: 20.00, name: "Bamboo Socks Cats", quantity_by_size: {s: 7, m: 2}}
]).total_stock
# => 36
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