Enumerator::ArithmeticSequence is a subclass of Enumerator, that is a representation of sequences of numbers with common difference. Instances of this class can be generated by the Range#step and Numeric#step methods.
The class can be used for slicing Array (see Array#slice) or custom collections.
A pointer to a C structure
Subclass of Zlib::Error
When zlib returns a Z_VERSION_ERROR, usually if the zlib library version is incompatible with the version assumed by the caller.
This file provides the CGI::Session class, which provides session support for CGI scripts. A session is a sequence of HTTP requests and responses linked together and associated with a single client. Information associated with the session is stored on the server between requests. A session id is passed between client and server with every request and response, transparently to the user. This adds state information to the otherwise stateless HTTP request/response protocol.
A CGI::Session instance is created from a CGI object. By default, this CGI::Session instance will start a new session if none currently exists, or continue the current session for this client if one does exist. The new_session option can be used to either always or never create a new session. See new() for more details.
delete() deletes a session from session storage. It does not however remove the session id from the client. If the client makes another request with the same id, the effect will be to start a new session with the old session’s id.
The Session class associates data with a session as key-value pairs. This data can be set and retrieved by indexing the Session instance using ‘[]’, much the same as hashes (although other hash methods are not supported).
When session processing has been completed for a request, the session should be closed using the close() method. This will store the session’s state to persistent storage. If you want to store the session’s state to persistent storage without finishing session processing for this request, call the update() method.
The caller can specify what form of storage to use for the session’s data with the database_manager option to CGI::Session::new. The following storage classes are provided as part of the standard library:
CGI::Session::FileStore
stores data as plain text in a flat file. Only works with String data. This is the default storage type.
CGI::Session::MemoryStore
stores data in an in-memory hash. The data only persists for as long as the current Ruby interpreter instance does.
CGI::Session::PStore
stores data in Marshalled format. Provided by cgi/session/pstore.rb. Supports data of any type, and provides file-locking and transaction support.
Custom storage types can also be created by defining a class with the following methods:
new(session, options) restore # returns hash of session data. update close delete
Changing storage type mid-session does not work. Note in particular that by default the FileStore and PStore session data files have the same name. If your application switches from one to the other without making sure that filenames will be different and clients still have old sessions lying around in cookies, then things will break nastily!
Most session state is maintained on the server. However, a session id must be passed backwards and forwards between client and server to maintain a reference to this session state.
The simplest way to do this is via cookies. The CGI::Session class provides transparent support for session id communication via cookies if the client has cookies enabled.
If the client has cookies disabled, the session id must be included as a parameter of all requests sent by the client to the server. The CGI::Session class in conjunction with the CGI class will transparently add the session id as a hidden input field to all forms generated using the CGI#form() HTML generation method. No built-in support is provided for other mechanisms, such as URL re-writing. The caller is responsible for extracting the session id from the session_id attribute and manually encoding it in URLs and adding it as a hidden input to HTML forms created by other mechanisms. Also, session expiry is not automatically handled.
require 'cgi' require 'cgi/session' require 'cgi/session/pstore' # provides CGI::Session::PStore cgi = CGI.new("html4") session = CGI::Session.new(cgi, 'database_manager' => CGI::Session::PStore, # use PStore 'session_key' => '_rb_sess_id', # custom session key 'session_expires' => Time.now + 30 * 60, # 30 minute timeout 'prefix' => 'pstore_sid_') # PStore option if cgi.has_key?('user_name') and cgi['user_name'] != '' # coerce to String: cgi[] returns the # string-like CGI::QueryExtension::Value session['user_name'] = cgi['user_name'].to_s elsif !session['user_name'] session['user_name'] = "guest" end session.close
require 'cgi' require 'cgi/session' cgi = CGI.new("html4") # We make sure to delete an old session if one exists, # not just to free resources, but to prevent the session # from being maliciously hijacked later on. begin session = CGI::Session.new(cgi, 'new_session' => false) session.delete rescue ArgumentError # if no old session end session = CGI::Session.new(cgi, 'new_session' => true) session.close
Timer id conversion keeps objects alive for a certain amount of time after their last access. The default time period is 600 seconds and can be changed upon initialization.
To use TimerIdConv:
DRb.install_id_conv TimerIdConv.new 60 # one minute
An implementation of PseudoPrimeGenerator which uses a prime table generated by trial division.
Internal use. An implementation of prime table by trial division method.
Raised when trying to activate a gem, and the gem exists on the system, but not the requested version. Instead of rescuing from this class, make sure to rescue from the superclass Gem::LoadError to catch all types of load errors.
Raised when there are conflicting gem specs loaded
Raised when a gem dependencies file specifies a ruby version that does not match the current version.
The Version class processes string versions into comparable values. A version string should normally be a series of numbers separated by periods. Each part (digits separated by periods) is considered its own number, and these are used for sorting. So for instance, 3.10 sorts higher than 3.2 because ten is greater than two.
If any part contains letters (currently only a-z are supported) then that version is considered prerelease. Versions with a prerelease part in the Nth part sort less than versions with N-1 parts. Prerelease parts are sorted alphabetically using the normal Ruby string sorting rules. If a prerelease part contains both letters and numbers, it will be broken into multiple parts to provide expected sort behavior (1.0.a10 becomes 1.0.a.10, and is greater than 1.0.a9).
Prereleases sort between real releases (newest to oldest):
1.0
1.0.b1
1.0.a.2
0.9
If you want to specify a version restriction that includes both prereleases and regular releases of the 1.x series this is the best way:
s.add_dependency 'example', '>= 1.0.0.a', '< 2.0.0'
Users expect to be able to specify a version constraint that gives them some reasonable expectation that new versions of a library will work with their software if the version constraint is true, and not work with their software if the version constraint is false. In other words, the perfect system will accept all compatible versions of the library and reject all incompatible versions.
Libraries change in 3 ways (well, more than 3, but stay focused here!).
The change may be an implementation detail only and have no effect on the client software.
The change may add new features, but do so in a way that client software written to an earlier version is still compatible.
The change may change the public interface of the library in such a way that old software is no longer compatible.
Some examples are appropriate at this point. Suppose I have a Stack class that supports a push and a pop method.
Switch from an array based implementation to a linked-list based implementation.
Provide an automatic (and transparent) backing store for large stacks.
Add a depth method to return the current depth of the stack.
Add a top method that returns the current top of stack (without changing the stack).
Change push so that it returns the item pushed (previously it had no usable return value).
Changes pop so that it no longer returns a value (you must use top to get the top of the stack).
Rename the methods to push_item and pop_item.
Rational Versioning Versions shall be represented by three non-negative integers, separated by periods (e.g. 3.1.4). The first integers is the “major” version number, the second integer is the “minor” version number, and the third integer is the “build” number.
A category 1 change (implementation detail) will increment the build number.
A category 2 change (backwards compatible) will increment the minor version number and reset the build number.
A category 3 change (incompatible) will increment the major build number and reset the minor and build numbers.
Any “public” release of a gem should have a different version. Normally that means incrementing the build number. This means a developer can generate builds all day long, but as soon as they make a public release, the version must be updated.
Let’s work through a project lifecycle using our Stack example from above.
Version 0.0.1
The initial Stack class is release.
Version 0.0.2
Switched to a linked=list implementation because it is cooler.
Version 0.1.0
Added a depth method.
Version 1.0.0
Added top and made pop return nil (pop used to return the old top item).
Version 1.1.0
push now returns the value pushed (it used it return nil).
Version 1.1.1
Fixed a bug in the linked list implementation.
Version 1.1.2
Fixed a bug introduced in the last fix.
Client A needs a stack with basic push/pop capability. They write to the original interface (no top), so their version constraint looks like:
gem 'stack', '>= 0.0'
Essentially, any version is OK with Client A. An incompatible change to the library will cause them grief, but they are willing to take the chance (we call Client A optimistic).
Client B is just like Client A except for two things: (1) They use the depth method and (2) they are worried about future incompatibilities, so they write their version constraint like this:
gem 'stack', '~> 0.1'
The depth method was introduced in version 0.1.0, so that version or anything later is fine, as long as the version stays below version 1.0 where incompatibilities are introduced. We call Client B pessimistic because they are worried about incompatible future changes (it is OK to be pessimistic!).
Version Catastrophe: From: blog.zenspider.com/2008/10/rubygems-howto-preventing-cata.html
Let’s say you’re depending on the fnord gem version 2.y.z. If you specify your dependency as “>= 2.0.0” then, you’re good, right? What happens if fnord 3.0 comes out and it isn’t backwards compatible with 2.y.z? Your stuff will break as a result of using “>=”. The better route is to specify your dependency with an “approximate” version specifier (“~>”). They’re a tad confusing, so here is how the dependency specifiers work:
Specification From ... To (exclusive) ">= 3.0" 3.0 ... ∞ "~> 3.0" 3.0 ... 4.0 "~> 3.0.0" 3.0.0 ... 3.1 "~> 3.5" 3.5 ... 4.0 "~> 3.5.0" 3.5.0 ... 3.6 "~> 3" 3.0 ... 4.0
For the last example, single-digit versions are automatically extended with a zero to give a sensible result.
Raised by transcoding methods when a named encoding does not correspond with a known converter.