Class: RESTFramework::Paginators::PageNumberPaginator

Inherits:
BasePaginator
  • Object
show all
Defined in:
lib/rest_framework/paginators/page_number_paginator.rb

Overview

A simple paginator based on page numbers.

Example: http://example.com/api/users/?page=3&page_size=50

Instance Method Summary collapse

Constructor Details

#initialize(**kwargs) ⇒ PageNumberPaginator

Returns a new instance of PageNumberPaginator.



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# File 'lib/rest_framework/paginators/page_number_paginator.rb', line 5

def initialize(**kwargs)
  super
  @page_size = self._page_size
  @total_count = @controller.class.page_total_count

  # Compute the total count (and total pages) unless disabled. On large tables `page_total_count`
  # can be set to `false` to skip this `COUNT(*)` over the whole filtered set; `next` is then
  # derived by fetching one extra record in `get_page`.
  if @total_count
    # Exclude any `select` clauses, since that would cause `count` to fail with a SQL
    # `SyntaxError`.
    @count = @data.except(:select).count
    @total_pages = @count / @page_size
    @total_pages += 1 if @count % @page_size != 0
  end
end

Instance Method Details

#_page_size ⇒ Object 



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# File 'lib/rest_framework/paginators/page_number_paginator.rb', line 22

def _page_size
  page_size = nil

  # Get from query param, if allowed.
  if param = @controller.class.page_size_query_param
    if raw = @controller.request.query_parameters[param].presence
      parsed = raw.to_i
      page_size = parsed if parsed > 0
    end
  end

  # Fall back to the configured page size.
  page_size ||= @controller.class.page_size&.to_i || 1

  # Ensure we don't exceed the max page size.
  max_page_size = @controller.class.max_page_size
  if max_page_size && page_size > max_page_size
    page_size = max_page_size
  end

  # Ensure we return at least 1.
  [ page_size, 1 ].max
end

#get_page(page_number = nil) ⇒ Object

Get the page and return it so the caller can serialize it.



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# File 'lib/rest_framework/paginators/page_number_paginator.rb', line 47

def get_page(page_number = nil)
  # If page number isn't provided, infer from the query params or use 1 as a fallback value.
  unless page_number
    page_number = @controller&.request&.query_parameters&.[](@controller.class.page_query_param)
    if page_number.blank?
      page_number = 1
    else
      page_number = page_number.to_i
      if page_number < 1
        page_number = 1
      end
    end
  end
  @page_number = page_number

  # Get the data page and return it so the caller can serialize the data in the proper format.
  page_index = @page_number - 1
  offset = page_index * @page_size

  # Without a total count we can't derive `next` from `total_pages`, so detect whether a further
  # page exists with a cheap existence check (a `LIMIT 1` past this page) instead of a full count.
  unless @total_count
    @has_next = @data.except(:select).offset(offset + @page_size).exists?
  end

  @data.limit(@page_size).offset(offset)
end

#get_paginated_response(serialized_page) ⇒ Object

Wrap the serialized page with appropriate metadata.



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# File 'lib/rest_framework/paginators/page_number_paginator.rb', line 76

def get_paginated_response(serialized_page)
  page_query_param = @controller.class.page_query_param
  base_params = @controller.request.query_parameters.symbolize_keys
  has_next = @total_count ? @page_number < @total_pages : @has_next
  next_url = if has_next
    @controller.url_for({ **base_params, page_query_param => @page_number + 1 })
  end
  previous_url = if @page_number > 1
    @controller.url_for({ **base_params, page_query_param => @page_number - 1 })
  end

  {
    count: @count,
    page: @page_number,
    page_size: @page_size,
    total_pages: @total_pages,
    next: next_url,
    previous: previous_url,
    results: serialized_page,
  }.compact
end