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# XQuery [](https://gitter.im/JelF/xquery?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [](https://travis-ci.org/JelF/xquery) [](https://codeclimate.com/github/JelF/xquery) [](https://codeclimate.com/github/JelF/xquery/coverage) [](https://codeclimate.com/github/JelF/xquery) XQuery is designed to replace boring method call chains and allow to easier convert it in a builder classes ## Usage of `XQuery` function `XQuery` is a shortcat to `XQuery::Generic.with` ``` r = XQuery(''.html_safe) do |q| # similar to tap q << 'bla bla bla' q << 'bla bla bla' # using truncate q.truncate(15) # real content (q.send(:query)) mutated q << '!' end r # => "bla bla blab...!" ``` ## Usage of `XQuery::Abstract` I designed this gem to help me with `ActiveRecord` Queries, so i inherited `XQuery::Abstract` and used it's powers. It provides the following features ### `wrap_method` and `wrap_methods` when you call each of this methods they became automatically wrapped (`XQuery::Abstract` basically wraps all methods query `#respond_to?`) It means, that there are instance methods with same name defined and will change a `#query` to their call result. ``` self.query = query.foo(x) # is basically the same as foo(x) # when `wrap_method :foo` called ``` You can also specify new name using `wrap_method :foo, as: :bar` syntax ### `q` object `q` is a proxy object which holds all of wrapped methods, but not methods you defined inside your class. E.g. i have defined `wrap_method(:foo)`, but also delegated `#foo` to some another object. If i call `q.foo`, i will get wrapped method. Note, that if you redefine `#__foo` method, q.foo will call it instead of normal work. You can add additional methods to `q` using something like `alias_on_q :foo`. I used it with `kaminary` and it was useful ``` def page=(x) apply { |query| query.page(x) } end alias_on_q :page= def page query.current_page end alias_on_q :page ``` ### `query_superclass` You should specify `query_superclass` class_attribute to inherit `XQuery::Abstract`. Whenever `query.is_a?(query_superclass)` evaluate to false, you will get `XQuery::QuerySuperclassChanged` exception. It can save you much time when your class misconfigured. E.g. you are using `select!` and it returns `nil`, because why not? ### `#apply` method `#apply` does exact what it source tells ``` # yields query inside block # @param block [#to_proc] # @return [XQuery::Abstract] self def apply(&block) self.query = block.call(query) self end ``` It is usefull to merge different queries. ### `with` class method You can get XQuery functionality even you have not defined a specific class (You are still have to inherit XQuery::Abstract to use it) You can see it in this document when i described `XQuery` function. Note, that it yields a class instance, not `q` object. It accepts any arguments, they will be passed to a constructor (except block) ### `execute` method Preferred way to call public instance methods. Resulting query would be returned

Value Value is a library for defining immutable value objects in Ruby. A value object is an object whose equality to other objects is determined by its value, not its identity, think dates and amounts of money. A value object should also be immutable, as you don’t want the date “2013-04-22” itself to change but the current date to change from “2013-04-22” to “2013-04-23”. That is, you don’t want entries in a calendar for 2013-04-22 to move to 2013-04-23 simply because the current date changes from 2013-04-22 to 2013-04-23. A value object consists of one or more attributes stored in instance variables. Value sets up an #initialize method for you that let’s you set these attributes, as, value objects being immutable, this’ll be your only chance to do so. Value also adds equality checks ‹#==› and ‹#eql?› (which are themselves equivalent), a ‹#hash› method, a nice ‹#inspect› method, and a protected attribute reader for each attribute. You may of course add any additional methods that your value object will benefit from. That’s basically all there’s too it. Let’s now look at using the Value library. § Usage You create value object class by invoking ‹#Value› inside the class (module) you wish to make into a value object class. Let’s create a class that represent points on a plane: class Point Value :x, :y end A ‹Point› is thus a value object consisting of two sub-values ‹x› and ‹y› (the coordinates). Just from invoking ‹#Value›, a ‹Point› object will have a constructor that takes two arguments to set instance variables ‹@x› and ‹@y›, equality checks ‹#==› and ‹#eql?› (which are the same), a ‹#hash› method, a nice ‹#inspect› method, and two protected attribute readers ‹#x› and ‹#y›. We can thus already creat ‹Point›s: origo = Point.new(0, 0) The default of making the attribute readers protected is often good practice, but for a ‹Point› it probably makes sense to be able to access its coordinates: class Point public(*attributes) end This’ll make all attributes of ‹Point› public. You can of course choose to only make certain attributes public: class Point public :x end Note that this public is standard Ruby functionality. Adding a method to ‹Point› is of course also possible and very much Rubyish: class Point def distance(other) Math.sqrt((other.x - x)**2 + (other.y - y)**2) end end For some value object classes you might want to support optional attributes. This is done by providing a default value for the attribute, like so: class Money Value :amount, [:currency, :USD] end Here, the ‹currency› attribute will default to ‹:USD›. You can create ‹Money› via dollars = Money.new(2) but also kronor = Money.new(2, :SEK) All required attributes must come before any optional attributes. Splat attributes are also supported: class List Value :'*elements' end empty = List.new suits = List.new(:spades, :hearts, :diamonds, :clubs) Splat attributes are optional. Finally, block attributes are also available: class Block Value :'&block' end block = Block.new{ |e| e * 2 } Block attributes are optional. Comparison beyond ‹#==› is possible by specifingy the ‹:comparable› option to ‹#Value›, listing one or more attributes that should be included in the comparison: class Vector Value :a, :b, :comparable => :a end Note that equality (‹#==› and ‹#eql?›) is always defined based on all attributes, regardless of arguments to ‹:comparable›. Here we say that comparisons between ‹Vector›s should be made between the values of the ‹a› attribute only. We can also make comparisons between all attributes of a value object: class Vector Value :a, :b, :comparable => true end To sum things up, let’s use all possible arguments to ‹#Value› at once: class Method Value :file, :line, [:name, 'unnamed'], :'*args', :'&block', :comparable => [:file, :line] end A ‹Method› consists of file and line information, a possible name, some arguments, possibly a block, and is comparable on the file and line on which they appear. Check out the {full API documentation}¹ for a more explicit description, should you need it or should you want to extend it. ¹ See http://disu.se/software/value/api/ § Financing Currently, most of my time is spent at my day job and in my rather busy private life. Please motivate me to spend time on this piece of software by donating some of your money to this project. Yeah, I realize that requesting money to develop software is a bit, well, capitalistic of me. But please realize that I live in a capitalistic society and I need money to have other people give me the things that I need to continue living under the rules of said society. So, if you feel that this piece of software has helped you out enough to warrant a reward, please PayPal a donation to now@disu.se¹. Thanks! Your support won’t go unnoticed! ¹ Send a donation: https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=now%40disu%2ese&item_name=Value § Reporting Bugs Please report any bugs that you encounter to the {issue tracker}¹. ¹ See https://github.com/now/value/issues § Authors Nikolai Weibull wrote the code, the tests, the manual pages, and this README. § Licensing Value is free software: you may redistribute it and/or modify it under the terms of the {GNU Lesser General Public License, version 3}¹ or later², as published by the {Free Software Foundation}³. ¹ See http://disu.se/licenses/lgpl-3.0/ ² See http://gnu.org/licenses/ ³ See http://fsf.org/

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