Class: Candid::Internal::OffsetPageIterator

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/candid/internal/iterators/offset_page_iterator.rb

Instance Method Summary collapse

Constructor Details

#initialize(initial_page:, item_field:, has_next_field:, step:, &block) ⇒ Candid::Internal::OffsetPageIterator

Instantiates an OffsetPageIterator, an Enumerable class which wraps calls to an offset-based paginated API and yields pages of items from it.

Parameters:

  • initial_page (Integer) —

    The initial page to use when iterating, if any.

  • item_field (Symbol) —

    The field to pull the list of items to iterate over.

  • has_next_field (Symbol) —

    The field to pull the boolean of whether a next page exists from, if any.

  • step (Boolean) —

    If true, treats the page number as a true offset (i.e. increments the page number by the number of items returned from each call rather than just 1)

  • block (Proc) —

    A block which is responsible for receiving a page number to use and returning the given page from the API.



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# File 'lib/candid/internal/iterators/offset_page_iterator.rb', line 16

def initialize(initial_page:, item_field:, has_next_field:, step:, &block)
  @page_number = initial_page || (step ? 0 : 1)
  @item_field = item_field
  @has_next_field = has_next_field
  @step = step
  @get_next_page = block

  # A cache of whether the API has another page, if it gives us that information...
  @next_page = nil
  # ...or the actual next page, preloaded, if it doesn't.
  @has_next_page = nil
end

Instance Method Details

#each(&block) ⇒ NilClass

Iterates over each page returned by the API.

Parameters:

  • block (Proc) —

    The block which each retrieved page is yielded to.

Returns:

  • (NilClass) 


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# File 'lib/candid/internal/iterators/offset_page_iterator.rb', line 33

def each(&block)
  while (page = get_next)
    block.call(page)
  end
end

#get_next ⇒ Object

Returns the next page from the API.



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# File 'lib/candid/internal/iterators/offset_page_iterator.rb', line 57

def get_next
  return nil if @page_number.nil?

  if @next_page
    this_page = @next_page
    @next_page = nil
  else
    this_page = @get_next_page.call(@page_number)
  end

  @has_next_page = this_page&.send(@has_next_field) if @has_next_field

  items = this_page.send(@item_field)
  if items.nil? || items.empty?
    @page_number = nil
    return nil
  elsif @step
    @page_number += items.length
  else
    @page_number += 1
  end

  this_page
end

#has_next? ⇒ Boolean

Whether another page will be available from the API.

Returns:

  • (Boolean) 


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# File 'lib/candid/internal/iterators/offset_page_iterator.rb', line 42

def has_next?
  return @has_next_page unless @has_next_page.nil?
  return true if @next_page

  next_page = @get_next_page.call(@page_number)
  next_page_items = next_page&.send(@item_field)
  if next_page_items.nil? || next_page_items.empty?
    @has_next_page = false
  else
    @next_page = next_page
    true
  end
end