.NET/ASP.NET/C#/VB.NET PDF Document SDK

Note The database handle has been assigned to a global variable, $db, so that you can split your program into multiple methods without creating a class. You can therefore access the database handle, $db, from anywhere you wish.

To cope with the closing situation, you ll create a method specifically for disconnecting the database and ending the program:

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PowerPoint includes a range of drawing tools that you might already know how to use, such as creating shapes, lines, arrows, callouts, charts, and graphs. You can add any of these elements as a simple graphic on a slide or use the drawing tools to add other

Tip There is a standard library module called bisect, which implements binary search very efficiently.

Now let s create a method that will use the CREATE TABLE SQL statement to create the table where you ll store your data:

def create_table puts "Creating people table" $db.execute %q{ CREATE TABLE people ( id integer primary key, name varchar(50), job varchar(50), gender varchar(6), age integer) } end

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A database handle will allow you to execute arbitrary SQL with the execute method. All you need to do is pass the SQL as an argument, and SQLite will execute the SQL upon the database. Next, let s create a method that asks for input from the user to add a new person to the database:

def add_person puts "Enter name:" name = gets.chomp puts "Enter job:" job = gets.chomp puts "Enter gender:" gender = gets.chomp puts "Enter age:" age = gets.chomp $db.execute("INSERT INTO people (name, job, gender, age) VALUES ( , , , )", name, job, gender, age) end

By now, you are probably used to using functions just like other objects (strings, number, sequences, and so on) by assigning them to variables, passing them as parameters, and returning them from other functions. Some programming languages (such as Scheme or LISP) use functions in this way to accomplish almost everything. Even though you usually don t rely that heavily on functions in Python (you usually make your own kinds of objects more about that in the next chapter), you can. This section describes a few functions that are useful for this sort of functional programming. These functions are map, filter, reduce, and apply.

Note The chomp method added to gets removes the newline characters that appear at the end of keyboard output retrieved with gets.

graphical elements such as callouts to existing photographs. And if you know other illustration software or know people who do, you have that many more resources.

The start of the add_person method is mundane. You ask for each of the person s attributes in turn and assign them to variables. However, the $db.execute is more intriguing this time. In the previous section, the INSERT SQL was shown with the data in the main statement, but in this method you re using question marks ( ) as placeholders for the data. Ruby performs an automatic substitution from the other parameters passed to execute into the placeholders. This acts as a way of securing your database. The reason is that if you interpolated the user s input directly into the SQL, the user might type some SQL that could break your query. However, when you use the placeholder method, the SQLite-Ruby library will clean up the supplied data for you and make sure it s safe to put into the database. Now you need a way to be able to access the data entered. Time for another method! This code example shows how to retrieve person data for a given name and ID:

def find_person puts "Enter name or ID of person to find:" id = gets.chomp person = $db.execute("SELECT * FROM people WHERE name = OR id = ", id, id.to_i).first unless person puts "No result found" return end puts %Q{Name: #{person['name']} Job: #{person['job']} Gender: #{person['gender']} Age: #{person['age']}} end