Class: Nitro::Pager

Inherits:
Object
  • Object
show all
Defined in:
lib/nitro/helper/pager.rb

Overview

Displays a collection of entitities in multiple pages.

Design

This pager is carefully designed for scaleability. It stores only the items for one page. The key parameter is needed, multiple pagers can coexist in a single page. The pager leverages the SQL LIMIT option to optimize database interaction.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(request, per_page, total_count, key = Pager.key) ⇒ Pager

Returns a new instance of Pager.



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# File 'lib/nitro/helper/pager.rb', line 42

def initialize(request, per_page, total_count, key = Pager.key)
  raise 'per_page should be > 0' unless per_page > 0

  @request, @key = request, key
  @page = request.query.fetch(key, 1).to_i
  @per_page = per_page
  set_count(total_count)
  @start_idx = (@page - 1) * per_page    
end

Instance Attribute Details

#page ⇒ Object

The current page.



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# File 'lib/nitro/helper/pager.rb', line 28

def page
  @page
end

#page_count ⇒ Object

The total number of pages.



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# File 'lib/nitro/helper/pager.rb', line 36

def page_count
  @page_count
end

#per_page ⇒ Object

Items per page.



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# File 'lib/nitro/helper/pager.rb', line 32

def per_page
  @per_page
end

#total_count ⇒ Object

Total count of items.



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# File 'lib/nitro/helper/pager.rb', line 40

def total_count
  @total_count
end

Instance Method Details

#each(&block) ⇒ Object

Iterator



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# File 'lib/nitro/helper/pager.rb', line 107

def each(&block)
  @page_items.each(&block)
end

#each_with_index ⇒ Object

Iterator Returns 1-based index.



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# File 'lib/nitro/helper/pager.rb', line 114

def each_with_index
  idx = @start_idx
  for item in @page_items
    yield(idx + 1, item)
    idx += 1
  end
end

#empty? ⇒ Boolean

Is the pager empty, ie has one page only?

Returns:

  • (Boolean) 


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# File 'lib/nitro/helper/pager.rb', line 124

def empty?
  return @page_count < 1
end

#first_page ⇒ Object

Return the first page index.



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# File 'lib/nitro/helper/pager.rb', line 59

def first_page
  return 1
end

#first_page? ⇒ Boolean

Is the first page displayed?

Returns:

  • (Boolean) 


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# File 'lib/nitro/helper/pager.rb', line 65

def first_page?
  @page == 1
end

#last_page ⇒ Object

Return the last page index.



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# File 'lib/nitro/helper/pager.rb', line 71

def last_page 
  return @page_count
end

#last_page? ⇒ Boolean

Is the last page displayed?

Returns:

  • (Boolean) 


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# File 'lib/nitro/helper/pager.rb', line 77

def last_page?
  @page == @page_count
end

#limit ⇒ Object

To be used with Og queries.



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# File 'lib/nitro/helper/pager.rb', line 158

def limit
  if @start_idx > 0
    { :limit => @per_page, :offset => @start_idx }
  else
    { :limit => @per_page }
  end
end

#nav_range ⇒ Object

Override if needed.



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# File 'lib/nitro/helper/pager.rb', line 145

def nav_range
  # effective range = 10 pages.
  s = [@page - 5, 1].max()
  e = [@page + 9, @page_count].min()
  
  d = 9 - (e - s)
  e += d if d < 0
  
  return (s..e)
end

#navigation ⇒ Object Also known as: links

Override this method in your application if needed. – TODO: better markup. ++



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# File 'lib/nitro/helper/pager.rb', line 187

def navigation
  nav = ""
  
  unless first_page?
    nav << %{
      <div class="first"><a href="#{first_page_href}">First</a></div>
      <div class="previous"><a href="#{previous_page_href}">Previous</a></div>
    }
  end
  
  unless last_page?
    nav << %{
      <div class="last"><a href="#{last_page_href}">Last</a></div>
      <div class="next"><a href="#{next_page_href}">Next</a></div>
    }
  end

  nav << %{<ul>}
  
  for i in nav_range()
    if i == @page
      nav << %{
        <li class="active">#{i}</li>
      }
    else
      nav << %{
        <li><a href="#{target_uri(i)}">#{i}</a></li>
      }      
    end
  end
  
  nav << %{</ul>}
  
  return nav
end

#navigation_needed? ⇒ Boolean Also known as: navigation?

Returns:

  • (Boolean) 


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# File 'lib/nitro/helper/pager.rb', line 224

def navigation_needed?
  @page_count > 1
end

#next_page ⇒ Object

Return the index of the next page.



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# File 'lib/nitro/helper/pager.rb', line 89

def next_page
  return [@page + 1, @page_count].min()
end

#offset ⇒ Object 



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# File 'lib/nitro/helper/pager.rb', line 166

def offset 
  @start_idx
end

#page_range ⇒ Object

Returns the range of the current page.



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# File 'lib/nitro/helper/pager.rb', line 136

def page_range
  s = @idx
  e = [@idx + @items_per_page - 1, all_total_count].min
  
  return [s, e]
end

#previous_page ⇒ Object

Return the index of the previous page.



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# File 'lib/nitro/helper/pager.rb', line 83

def previous_page
  return [@page - 1, 1].max()
end

#set_count(total_count) ⇒ Object 



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# File 'lib/nitro/helper/pager.rb', line 52

def set_count(total_count)
  @total_count = total_count
  @page_count = (@total_count.to_f / @per_page).ceil
end

#size ⇒ Object

The items count.



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# File 'lib/nitro/helper/pager.rb', line 130

def size
  return @total_count
end

#to_sql ⇒ Object

Create an appropriate SQL limit clause. Returns postgres/mysql compatible limit.



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# File 'lib/nitro/helper/pager.rb', line 173

def to_sql
  if @start_idx > 0
    return "LIMIT #{@per_page} OFFSET #{@start_idx}"
  else
    # gmosx: perhaps this is optimized ? naaaaaah...
    return "LIMIT #{@per_page}"
  end
end