This module is used to manager HTTP status codes.
See www.w3.org/Protocols/rfc2616/rfc2616-sec10.html for more information.
A String
object holds and manipulates an arbitrary sequence of bytes, typically representing characters. String
objects may be created using String::new
or as literals.
Because of aliasing issues, users of strings should be aware of the methods that modify the contents of a String
object. Typically, methods with names ending in “!” modify their receiver, while those without a “!” return a new String
. However, there are exceptions, such as String#[]=
.
Raised by exit
to initiate the termination of the script.
Raised when encountering an object that is not of the expected type.
[1, 2, 3].first("two")
raises the exception:
TypeError: no implicit conversion of String into Integer
Raised when the arguments are wrong and there isn’t a more specific Exception
class.
Ex: passing the wrong number of arguments
[1, 2, 3].first(4, 5)
raises the exception:
ArgumentError: wrong number of arguments (given 2, expected 1)
Ex: passing an argument that is not acceptable:
[1, 2, 3].first(-4)
raises the exception:
ArgumentError: negative array size
Raised when the given index is invalid.
a = [:foo, :bar] a.fetch(0) #=> :foo a[4] #=> nil a.fetch(4) #=> IndexError: index 4 outside of array bounds: -2...2
Raised when the specified key is not found. It is a subclass of IndexError
.
h = {"foo" => :bar} h.fetch("foo") #=> :bar h.fetch("baz") #=> KeyError: key not found: "baz"
Raised when a given numerical value is out of range.
[1, 2, 3].drop(1 << 100)
raises the exception:
RangeError: bignum too big to convert into `long'
ScriptError
is the superclass for errors raised when a script can not be executed because of a LoadError
, NotImplementedError
or a SyntaxError
. Note these type of ScriptErrors
are not StandardError
and will not be rescued unless it is specified explicitly (or its ancestor Exception
).
Raised when encountering Ruby code with an invalid syntax.
eval("1+1=2")
raises the exception:
SyntaxError: (eval):1: syntax error, unexpected '=', expecting $end
Raised when a file required (a Ruby script, extension library, …) fails to load.
require 'this/file/does/not/exist'
raises the exception:
LoadError: no such file to load -- this/file/does/not/exist
Raised when a feature is not implemented on the current platform. For example, methods depending on the fsync
or fork
system calls may raise this exception if the underlying operating system or Ruby runtime does not support them.
Note that if fork
raises a NotImplementedError
, then respond_to?(:fork)
returns false
.
Raised when a given name is invalid or undefined.
puts foo
raises the exception:
NameError: undefined local variable or method `foo' for main:Object
Since constant names must start with a capital:
Integer.const_set :answer, 42
raises the exception:
NameError: wrong constant name answer
Raised when a method is called on a receiver which doesn’t have it defined and also fails to respond with method_missing
.
"hello".to_ary
raises the exception:
NoMethodError: undefined method `to_ary' for "hello":String
A generic error class raised when an invalid operation is attempted. Kernel#raise
will raise a RuntimeError
if no Exception
class is specified.
raise "ouch"
raises the exception:
RuntimeError: ouch
Raised when there is an attempt to modify a frozen object.
[1, 2, 3].freeze << 4
raises the exception:
FrozenError: can't modify frozen Array
Raised when attempting a potential unsafe operation, typically when the $SAFE level is raised above 0.
foo = "bar" proc = Proc.new do $SAFE = 3 foo.untaint end proc.call
raises the exception:
SecurityError: Insecure: Insecure operation `untaint' at level 3
EncodingError
is the base class for encoding errors.
A Struct
is a convenient way to bundle a number of attributes together, using accessor methods, without having to write an explicit class.
The Struct
class generates new subclasses that hold a set of members and their values. For each member a reader and writer method is created similar to Module#attr_accessor
.
Customer = Struct.new(:name, :address) do def greeting "Hello #{name}!" end end dave = Customer.new("Dave", "123 Main") dave.name #=> "Dave" dave.greeting #=> "Hello Dave!"
See Struct::new
for further examples of creating struct subclasses and instances.
In the method descriptions that follow, a “member” parameter refers to a struct member which is either a quoted string ("name"
) or a Symbol
(:name
).