Class: N::UI::Pager

Inherits:
Array show all
Defined in:
lib/nitro/ui/pager.rb

Overview

Displays a collection of entitities in multiple pages.

Design

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

Example

@pager.set(N::BlogEntry.count)

default navigation (customize with css): <div class=“pager”>#@[email protected]</div>

custom navigation:

<table cellspacing=“0” width=“100%” border=“1”> <tr> <td width=“64”><x:pager-prev>Previous</x:pager-prev></td> <td width=“100%”></td> <td width=“64”><x:pager-next>Next</x:pager-next></td> </tr> </table> – INVESTIGATE: mysql> SELECT SQL_CALC_FOUND_ROWS * FROM tbl_name

-> WHERE id > 100 LIMIT 10;

mysql> SELECT FOUND_ROWS(); ++

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, request, items_per_page = 10, items = nil) ⇒ Pager

Returns a new instance of Pager.



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# File 'lib/nitro/ui/pager.rb', line 56

def initialize(name, request, items_per_page = 10, items = nil)
	raise "items_per_page should be > 0" unless items_per_page > 0

	@request, @name = request, name
	@page = request.query.fetch("__pg#{@name}", 1).to_i
	@items_per_page = items_per_page
	@start_idx = (@page - 1) * items_per_page
	
	if items
		set(items.size())			
		# gmosx, FIXME: not exactly what i want!
		items.slice!(@start_idx, @items_per_page)
	end
end

Instance Attribute Details

#idx ⇒ Object

Returns the value of attribute idx.



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# File 'lib/nitro/ui/pager.rb', line 45

def idx
  @idx
end

#name ⇒ Object

Returns the value of attribute name.



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# File 'lib/nitro/ui/pager.rb', line 45

def name
  @name
end

#page ⇒ Object

Returns the value of attribute page.



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# File 'lib/nitro/ui/pager.rb', line 45

def page
  @page
end

#page_count ⇒ Object

Returns the value of attribute page_count.



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# File 'lib/nitro/ui/pager.rb', line 45

def page_count
  @page_count
end

#page_items ⇒ Object

Page items



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# File 'lib/nitro/ui/pager.rb', line 51

def page_items
  @page_items
end

#request ⇒ Object

Read needed variables from the request.



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# File 'lib/nitro/ui/pager.rb', line 54

def request
  @request
end

#total_count ⇒ Object

Total count of items



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# File 'lib/nitro/ui/pager.rb', line 48

def total_count
  @total_count
end

Instance Method Details

#each(&block) ⇒ Object

Iterator



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# File 'lib/nitro/ui/pager.rb', line 94

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

#each_with_index ⇒ Object

Iterator Returns 1-based index.



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# File 'lib/nitro/ui/pager.rb', line 101

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

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/nitro/ui/pager.rb', line 109

def empty?
	return @items.empty?
end

#first_page ⇒ Object 



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# File 'lib/nitro/ui/pager.rb', line 76

def first_page
	return 1
end

#last_page ⇒ Object 



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# File 'lib/nitro/ui/pager.rb', line 80

def last_page 
	return @page_count
end

#nav_range ⇒ Object

Override if needed.



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# File 'lib/nitro/ui/pager.rb', line 128

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

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



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# File 'lib/nitro/ui/pager.rb', line 143

def navigation
	nav = ""
	
	unless @page == first_page()
		nav << %{
			<div class="first"><a href="#{target_uri(first_page())}">First</a></div>
			<div class="previous"><a href="#{target_uri(previous_page())}">Previous</a></div>
		}
	end
	
	unless @page == last_page()
		nav << %{
			<div class="last"><a href="#{target_uri(last_page())}">Last</a></div>
			<div class="next"><a href="#{target_uri(next_page())}">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

#next_page ⇒ Object 



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# File 'lib/nitro/ui/pager.rb', line 88

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

#offset ⇒ Object

Returns the current offset. The offset is zero-based.



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# File 'lib/nitro/ui/pager.rb', line 193

def offset
	(@page-1) * @items_per_page
end

#page_range ⇒ Object

Returns the range of the current page.



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# File 'lib/nitro/ui/pager.rb', line 119

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

#previous_page ⇒ Object 



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# File 'lib/nitro/ui/pager.rb', line 84

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

#set(total_count) ⇒ Object 



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

def set(total_count)
	@total_count = total_count
	@page_count = (@total_count.to_f() / @items_per_page).ceil()
end

#size ⇒ Object 



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# File 'lib/nitro/ui/pager.rb', line 113

def size
	return @items.size()
end

#sql_limit ⇒ Object

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



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# File 'lib/nitro/ui/pager.rb', line 182

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

#target_uri(page) ⇒ Object

Generate the target URI.



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# File 'lib/nitro/ui/pager.rb', line 199

def target_uri(page)
	params = {"__pg#{@name}" => page}
	return N::UriUtils.update_query_string(@request.uri.to_s, params)
end