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# The query extension adds Sequel::Dataset#query which allows
# a different way to construct queries instead of the usual
# method chaining.
module Sequel
class Database
# Return a dataset modified by the query block
def query(&block)
dataset.query(&block)
end
end
class Dataset
# Translates a query block into a dataset. Query blocks can be useful
# when expressing complex SELECT statements, e.g.:
#
# dataset = DB[:items].query do
# select :x, :y, :z
# filter{|o| (o.x > 1) & (o.y > 2)}
# order :z.desc
# end
#
# Which is the same as:
#
# dataset = DB[:items].select(:x, :y, :z).filter{|o| (o.x > 1) & (o.y > 2)}.order(:z.desc)
#
# Note that inside a call to query, you cannot call each, insert, update,
# or delete (or any method that calls those), or Sequel will raise an
# error.
def query(&block)
copy = clone({})
copy.extend(QueryBlockCopy)
copy.instance_eval(&block)
clone(copy.opts)
end
# Module used by Dataset#query that has the effect of making all
# dataset methods into !-style methods that modify the receiver.
module QueryBlockCopy
%w'each insert update delete'.each do |meth|
define_method(meth){|*args| raise Error, "##{meth} cannot be invoked inside a query block."}
end
# Merge the given options into the receiver's options and return the receiver
# instead of cloning the receiver.
def clone(opts = nil)
@opts.merge!(opts)
self
end
end
end
end
Version data entries
34 entries across 34 versions & 2 rubygems