Ruby Exceptions
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This document contains examples of error handling in Ruby using exceptions, rescue blocks, and custom error classes. It demonstrates raising different types of errors, accessing error details, and ensuring code is run after exceptions.
![class Book
attr_accessor :author, :page_count, :title
def initialize(args = {})
@author = args[:author]
self.page_count = args[:page_count]
@title = args[:title]
end
def page_count=(value)
min, max = 1, 1000
if value < min || value > max
raise RangeError, "Value of [#{value}] outside bounds of [#{min}] to
[#{max}]."
else
@page_count = value
end
end
end](https://image.slidesharecdn.com/rubyexeptions-190306091912/85/Ruby-Exceptions-5-320.jpg)
Ruby Exceptions
- 2. Array.hello #NoMethodError: undefined method `hello' for Array:Class #from (irb):3 #from /home/vladimir/.rvm/rubies/ruby-1.9.2-p0/bin/irb:17:in `<main>' hello #NameError: undefined local variable or method `hello' for main:Object #from (irb):4 #from /home/vladimir/.rvm/rubies/ruby-1.9.2-p0/bin/irb:17:in `<main>'
- 4. def my_method() raise "SomeError message ..." # raise "m" == raise RuntimeError.new("m") end my_method #exceptions.rb:2:in `my_method': SomeError message ... (RuntimeError) #from exceptions.rb:5:in `<main>'
- 5. class Book attr_accessor :author, :page_count, :title def initialize(args = {}) @author = args[:author] self.page_count = args[:page_count] @title = args[:title] end def page_count=(value) min, max = 1, 1000 if value < min || value > max raise RangeError, "Value of [#{value}] outside bounds of [#{min}] to [#{max}]." else @page_count = value end end end
- 6. begin 100 / 0 rescue puts "F! Divider is zero!" end #=> F! Divider is zero!
- 7. begin some_undefined_method_call rescue NameError puts "F! Undefined method!" end #=>F! Undefined method! def hello(msg = "") raise "Empty message!" if msg == "" puts(msg) rescue puts "Some Error!" end hello("Rubydev.ru") #Rubydev.ru hello #Some Error!
- 8. begin some_undefined_method_call rescue NameError p "F! Undefined method!" ensure p "RubyDev.ru" end #=>"F! Undefined method!" #=>"RubyDev.ru"
- 9. begin 3 / 0 rescue ZeroDivisionError => e puts "#{e.class}: #{e.message}" end begin "my string".odd? rescue NoMethodError => e puts "#{e.class}: #{e.message}" end
- 10. class MyError < StandardError attr_reader :thing def initialize(msg="My default message", thing="apple") @thing = thing super(msg) end end begin raise MyError.new("my message", "my thing") rescue => e puts e.thing # "my thing" end