Class: LazyList::ListBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/lazylist/list_builder.rb

Overview

This class encapsulates a list builder (ListBuilder), that can be transformed into a LazyList, by calling LazyList::ListBuilder#where.

Defined Under Namespace

Classes: ListBuilderProc

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(mode, &block) ⇒ ListBuilder

Creates LazyList::ListBuilder instance. mode has to be either :do_build or :do_comprehend.



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# File 'lib/lazylist/list_builder.rb', line 82

def initialize(mode, &block)
  @mode = mode
  @transform = ListBuilderProc.new(self, :transform, &block)
end

Instance Attribute Details

#filter ⇒ Object (readonly)

The filter ListBuilderProc of this list builder or nil.



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# File 'lib/lazylist/list_builder.rb', line 94

def filter
  @filter
end

#transform ⇒ Object (readonly)

The transform ListBuilderProc instance of this list builder.



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# File 'lib/lazylist/list_builder.rb', line 91

def transform
  @transform
end

#variables ⇒ Object (readonly)

The variable names defined in this list builder.



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# File 'lib/lazylist/list_builder.rb', line 88

def variables
  @variables
end

Class Method Details

.create_build(&block) ⇒ Object

Used to support the build method



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# File 'lib/lazylist/list_builder.rb', line 126

def create_build(&block)
  new(:do_build, &block)
end

.create_comprehend(&block) ⇒ Object

Used to evaluate a list comprehension, usually if calling the list method with only a block.



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# File 'lib/lazylist/list_builder.rb', line 132

def create_comprehend(&block)
  new(:do_comprehend, &block)
end

Instance Method Details

#to_s ⇒ Object Also known as: inspect

Return a (not much) nicer string representation of the list builder.



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# File 'lib/lazylist/list_builder.rb', line 119

def to_s
  "#<LazyList::ListBuilder>"
end

#where(sources = {}, &block) ⇒ Object

This method creates a LazyList instance from this list builder, using the sources hash to fetch the variables from. sources consists of the variable name and the values, that can be LazyList instances or otherwise they will be transformed into a LazyList with LazyList.[].

It also takes a block, to filter the results by a boolean expression.



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# File 'lib/lazylist/list_builder.rb', line 102

def where(sources = {}, &block)
  @variables = []
  generators = []
  sources.each do |var, src|
    @variables << var
    generators << (src.is_a?(LazyList) ? src : LazyList[src])
  end
  if block_given?
    @filter = ListBuilderProc.new(self, :filter, &block)
  else
    @filter = nil
  end
  generators.first.__send__(@mode, self, generators[1..-1])
end