# 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