Class: Seq::Paged

Inherits:
Seq
  • Object
show all
Defined in:
lib/seq/paged.rb

Overview

Paged seqs evaluate a block that returns a page (Array) of items that are then returned one at a time. This is useful for working with web services that return pages of results, when you need them as a list.

Examples:


s = Seq::Paged.new {|page| [page, page+1, page+2] }
s.take(10)  #=> [0, 1, 2,  1, 2, 3,  2, 3, 4,  3]
            #  extra spacing added to show pages

require 'flickraw'
# Authenticate FlickRaw...

f = Seq::Paged.new {|page|
  flickr.people.getPhotos(:user_id => 'me', :page => page).to_a
}
f.next #=> {"id"=>"8688497043", "owner"=>"75695140@N04", ...}
f.take(100).map {|photo| photo['title'] }.grep(/DSC/)
#=> ["DSC01485-edit", "DSC01485", "DSC01482-edit", "DSC01481", ...]

Constant Summary

Constants inherited from Seq

VERSION

Instance Method Summary collapse

Methods inherited from Seq

#each, #entries, #inc, #infinite?, #method_missing, #to_a

Constructor Details

#initialize(offset = 0, default = nil) {|page| ... } ⇒ Paged

Creates a new Paged seq instance.

Yields:

  • (page) —

    Block to be called which returns the next page of items

Yield Parameters:

  • page (Integer) —

    Page to be returned, begins at 0



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# File 'lib/seq/paged.rb', line 33

def initialize(offset=0, default=nil, &block)
  @block   = block
  @offset  = offset
  @default = default

  self.reset
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method in the class Seq

Instance Method Details

#ended? ⇒ Boolean 



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# File 'lib/seq/paged.rb', line 55

def ended?
  @index >= @items.size && @done
end

#next ⇒ Object 



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# File 'lib/seq/paged.rb', line 61

def next
  return @default if ended?

  while @items.size <= @index
    loaded = @block.call(@page)
    @page += 1
    if loaded.empty?
      @done = true
      return @default
    end
    @items += loaded
  end

  item = @items[@index]
  @index += 1
  item
end

#reset ⇒ Object

Resets the state of the paged seq. It also calculates any values necessary to get to the offset.



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# File 'lib/seq/paged.rb', line 43

def reset
  @index = 0
  @page  = 0
  @done  = false
  @items = []

  until @index >= @offset
    self.next
  end
end