class Gem::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'
How Software Changes¶ ↑
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.
Examples of Category 1 changes:¶ ↑
-
Switch from an array based implementation to a linked-list based implementation.
-
Provide an automatic (and transparent) backing store for large stacks.
Examples of Category 2 changes might be:¶ ↑
-
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).
Examples of Category 3 changes might be:¶ ↑
-
Changes
pop
so that it no longer returns a value (you must usetop
to get the top of the stack). -
Rename the methods to
push_item
andpop_item
.
RubyGems 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.
Examples¶ ↑
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 madepop
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!).
Preventing 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
Public Class Methods
True if the version
string matches RubyGems' requirements.
# File lib/rubygems/version.rb, line 167 def self.correct? version version.to_s =~ ANCHORED_VERSION_PATTERN end
Factory method to create a Version object. Input may be a Version or a String. Intended to simplify client code.
ver1 = Version.create('1.3.17') # -> (Version object) ver2 = Version.create(ver1) # -> (ver1) ver3 = Version.create(nil) # -> nil
# File lib/rubygems/version.rb, line 179 def self.create input if self === input then # check yourself before you wreck yourself input elsif input.nil? then nil else new input end end
Constructs a Version from the
version
string. A version string is a series of digits or
ASCII letters separated by dots.
# File lib/rubygems/version.rb, line 201 def initialize version raise ArgumentError, "Malformed version number string #{version}" unless self.class.correct?(version) @version = version.to_s.strip.gsub("-",".pre.") @segments = nil end
Public Instance Methods
Compares this version with other
returning -1, 0, or 1 if the
other version is larger, the same, or smaller than this one. Attempts to
compare to something that's not a Gem::Version
return
nil
.
# File lib/rubygems/version.rb, line 326 def <=> other return unless Gem::Version === other return 0 if @version == other.version lhsegments = segments rhsegments = other.segments lhsize = lhsegments.size rhsize = rhsegments.size limit = (lhsize > rhsize ? lhsize : rhsize) - 1 i = 0 while i <= limit lhs, rhs = lhsegments[i] || 0, rhsegments[i] || 0 i += 1 next if lhs == rhs return -1 if String === lhs && Numeric === rhs return 1 if Numeric === lhs && String === rhs return lhs <=> rhs end return 0 end
A recommended version for use with a ~> Requirement.
# File lib/rubygems/version.rb, line 310 def approximate_recommendation segments = self.segments.dup segments.pop while segments.any? { |s| String === s } segments.pop while segments.size > 2 segments.push 0 while segments.size < 2 "~> #{segments.join(".")}" end
Return a new version object where the next to the last revision number is one greater (e.g., 5.3.1 => 5.4).
Pre-release (alpha) parts, e.g, 5.3.1.b.2 => 5.4, are ignored.
# File lib/rubygems/version.rb, line 215 def bump segments = self.segments.dup segments.pop while segments.any? { |s| String === s } segments.pop if segments.size > 1 segments[-1] = segments[-1].succ self.class.new segments.join(".") end
Dump only the raw version string, not the complete object. It's a string for backwards (RubyGems 1.3.5 and earlier) compatibility.
# File lib/rubygems/version.rb, line 248 def marshal_dump [version] end
Load custom marshal format. It's a string for backwards (RubyGems 1.3.5 and earlier) compatibility.
# File lib/rubygems/version.rb, line 256 def marshal_load array initialize array[0] end
A version is considered a prerelease if it contains a letter.
# File lib/rubygems/version.rb, line 277 def prerelease? @prerelease ||= !!(@version =~ /[a-zA-Z]/) end
The release for this version (e.g. 1.2.0.a -> 1.2.0). Non-prerelease versions return themselves.
# File lib/rubygems/version.rb, line 289 def release return self unless prerelease? segments = self.segments.dup segments.pop while segments.any? { |s| String === s } self.class.new segments.join('.') end