Object
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
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.
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 for himself, but as soon as he/she makes 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. He writes to the original interface (no top), so his version constraint looks like:
gem 'stack', '~> 0.0'
Essentially, any version is OK with Client A. An incompatible change to the library will cause him grief, but he is willing to take the chance (we call Client A optimistic).
Client B is just like Client A except for two things: (1) He uses the depth method and (2) he is worried about future incompatibilities, so he writes his 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 he is worried about incompatible future changes (it is OK to be pessimistic!).
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 a “spermy” 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
True if the version string matches RubyGems’ requirements.
# File lib/rubygems/version.rb, line 160 160: def self.correct? version 161: version.to_s =~ ANCHORED_VERSION_PATTERN 162: 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 172 172: def self.create input 173: if input.respond_to? :version then 174: input 175: elsif input.nil? then 176: nil 177: else 178: new input 179: end 180: 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 186 186: def initialize version 187: raise ArgumentError, "Malformed version number string #{version}" unless 188: self.class.correct?(version) 189: 190: @version = version.to_s 191: @version.strip! 192: end
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 293 293: def <=> other 294: return unless Gem::Version === other 295: return 0 if @version == other.version 296: 297: lhsegments = segments 298: rhsegments = other.segments 299: 300: lhsize = lhsegments.size 301: rhsize = rhsegments.size 302: limit = (lhsize > rhsize ? lhsize : rhsize) - 1 303: 304: i = 0 305: 306: while i <= limit 307: lhs, rhs = lhsegments[i] || 0, rhsegments[i] || 0 308: i += 1 309: 310: next if lhs == rhs 311: return 1 if String === lhs && Numeric === rhs 312: return 1 if Numeric === lhs && String === rhs 313: 314: return lhs <=> rhs 315: end 316: 317: return 0 318: 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 200 200: def bump 201: segments = self.segments.dup 202: segments.pop while segments.any? { |s| String === s } 203: segments.pop if segments.size > 1 204: 205: segments[1] = segments[1].succ 206: self.class.new segments.join(".") 207: 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 229 229: def marshal_dump 230: [version] 231: end
Load custom marshal format. It’s a string for backwards (RubyGems 1.3.5 and earlier) compatibility.
# File lib/rubygems/version.rb, line 237 237: def marshal_load array 238: initialize array[0] 239: end
A version is considered a prerelease if it contains a letter.
# File lib/rubygems/version.rb, line 244 244: def prerelease? 245: @prerelease ||= @version =~ /[a-zA-Z]/ 246: 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 256 256: def release 257: return self unless prerelease? 258: 259: segments = self.segments.dup 260: segments.pop while segments.any? { |s| String === s } 261: self.class.new segments.join('.') 262: end
A recommended version for use with a ~> Requirement.
# File lib/rubygems/version.rb, line 277 277: def spermy_recommendation 278: segments = self.segments.dup 279: 280: segments.pop while segments.any? { |s| String === s } 281: segments.pop while segments.size > 2 282: segments.push 0 while segments.size < 2 283: 284: "~> #{segments.join(".")}" 285: end
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