Updating Records in an ORM Lab

Objectives

1. Build an #update method that updates an existing record.

Instructions

In this lab we will be working with a Student class. Each student has an id, a name and a grade. Students should be initialized with an id that defaults to nil, a name and a grade.

In this lab, our connection to the database is set up for you in the config/environment.rb file:

DB = {:conn => SQLite3::Database.new("db/students.db")}

In your Student class, you can access the database connection via: DB[:conn]

You'll be building the following methods:

The #initialize Method

This method takes in three arguments, the id, name and grade. The id should default to nil.

The .create_table Method

This class method creates the students table with columns that match the attributes of our individual students: an id (which is the primary key), the name and the grade.

The .drop_table Method

This class method should be responsible for dropping the students table.

The #save Method

This instance method inserts a new row into the database using the attributes of the given object. This method also assigns the id attribute of the object once the row has been inserted into the database.

The .create Method

This method creates a student with two attributes, name and grade, and saves it into the students table.

The .new_from_db Method

This class method takes an argument of an array. When we call this method we will pass it the array that is the row returned from the database by the execution of a SQL query. We can anticipate that this array will contain three elements in this order: the id, name and grade of a student.

The .new_from_db method uses these three array elements to create a new Student object with these attributes.

The .find_by_name Method

This class method takes in an argument of a name. It queries the database table for a record that has a name of the name passed in as an argument. Then it uses the #new_from_db method to instantiate a Student object with the database row that the SQL query returns.

The #update Method

This method updates the database row mapped to the given Student instance.

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