Exception Notes Day 1

Question 1

what is an exception?

Answer 1

Exceptions are what Ruby uses to deal with errors or other unexpected events. For now it’s okay to use exception and error synonymously.

Question 2

How do you design your code to handle exceptions gracefully?

Answer 2

by using the [begin…rescue] structure
Example:
num = 0
begin

Question 3

how does the [begin…end] structure work?

Answer 3

The behavior of begin…rescue is this: The code in the begin block will execute until an exception is reached. Once an exception is reached, the execution will immediately jump to rescue

Question 4

In the event that an exception is never hit in the begin block, then what will happen to the rescue block?

Answer 4

execution will never go to rescue.
Example:
num = 5
begin

Question 5

What does [raise] do

Answer 5

raise is how we bring up an exception.
Example:
def format_name(first, last)
if !(first.instance_of?(String) && last.instance_of?(String))
raise “arguments must be strings” “Grace Hopper”
format_name(42, true) # => RuntimeError: arguments
must be strings

Question 6

how do you use [raise] and [begin….rescue] together

Answer 6

An important distinction to note is that [raise] is how we bring up an exception, whereas [begin…rescue] is how we react to that exception.
Example:
def format_name(first, last)
if !(first.instance_of?(String) && last.instance_of?(String))
raise “arguments must be strings”
end

first.capitalize + “ “ + last.capitalize
end

first_name = 42
last_name = true
begin
  puts format_name(first_name, last_name)
rescue
  # do stuff to rescue the "arguments must be strings" exception...
  puts "there was an exception :("
end