core_tag_index_builder Class Reference

Helper to build tag index. More...

Public Member Functions
	__construct ($component, $itemtype, $sql, $params, $from, $limit)
	Constructor.
	can_access_course ($courseid)
	Checks if current user has access to the course.
	get_course ($courseid)
	Retrieves a course record (only fields id,visible,fullname,shortname,cacherev).
	get_items ()
	Returns the filtered records from SQL query result.
	has_item_that_needs_access_check ()
	Returns the first row from the SQL result that we don't know whether it is accessible by user or not.
	set_accessible ($identifier, $accessible=true)
	Marks record or group of records as accessible (or not accessible)
	walk ($callable)
	Walk through the array of items and call $callable for each of them.

Static Public Member Functions
static	reset_caches ()
	Resets all course/items session caches - useful in unittests when we change users and enrolments.

Protected Member Functions
	init_course_access ()
	Ensures that we read the course access from the cache.
	init_items_access ()
	Ensures that we read the items access from the cache.
	prepare_sql_courses ()
	Substitute COURSEFILTER% with an expression filtering out courses where current user does not have access.
	prepare_sql_items ()
	Substitute ITEMFILTER% with an expression filtering out items where current user does not have access.
	retrieve_items ()
	Ensures that SQL query was executed and $this->items is filled.
	save_caches ()
	Saves course/items caches if needed.

Protected Attributes
array	$accessibleitems
	cache of items accessibility (id => bool)
bool	$cachechangedaccessible = false
	indicates that items cache was changed in this class and needs pushing to MUC
bool	$cachechangedcourse = false
	indicates that course accessibiity cache was changed in this class and needs pushing to MUC
string	$component
	component specified in the constructor
array	$courseaccess
	cache of courses accessibility (courseid => bool)
array	$courses
	cached courses (not pushed to MUC)
int	$from
	index from which to return records
string	$idfield = 'id'
	alias of the item id in the SQL result
array	$itemkeys
	list of item ids ( array_keys($this->items) )
array	$items
	result of SQL query
string	$itemtype
	itemtype specified in the constructor
int	$limit
	maximum number of records to return
array	$params
	parameters for SQL statement
string	$sql
	SQL statement.

Detailed Description

Helper to build tag index.

This can be used by components to implement tag area callbacks. This is especially useful for in-course content when we need to check and cache user's access to multiple courses. Course access and accessible items are stored in session cache with 15 minutes expiry time.

Example of usage:

$builder = new core_tag_index_builder($component, $itemtype, $sql, $params, $from, $limit); while ($item = $builder->has_item_that_needs_access_check()) { if (!$builder->can_access_course($item->courseid)) { $builder->set_accessible($item, false); } else { $accessible = true; // Check access and set $accessible respectively. $builder->set_accessible($item, $accessible); } } $items = $builder->get_items();

Copyright

2016 Marina Glancy

License

http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

Constructor & Destructor Documentation

__construct()

core_tag_index_builder::__construct	(		$component,
			$itemtype,
			$sql,
			$params,
			$from,
			$limit )

Constructor.

Specify the SQL query for retrieving the tagged items, SQL query must:

• return the item id as the first field and make sure that it is unique in the result
• provide ORDER BY that exclude any possibility of random results, if $fromctx was specified when searching for tagged items it is the best practice to make sure that items from this context are returned first.

This query may also contain placeholders COURSEFILTER% or ITEMFILTER% that will be substituted with expressions excluding courses and/or filters that are already known as inaccessible.

Example: "WHERE c.id %COURSEFILTER% AND cm.id %ITEMFILTER%"

This query may contain fields to preload context if context is needed for formatting values.

It is recommended to sort by course sortorder first, this way the items from the same course will be next to each other and the sequence of courses will the same in different tag areas.

Parameters

string	$component	component responsible for tagging
string	$itemtype	type of item that is being tagged
string	$sql	SQL query that would retrieve all relevant items without permission check
array	$params	parameters for the query (must be named)
int	$from	return a subset of records, starting at this point
int	$limit	return a subset comprising this many records in total (this field is NOT optional)

Member Function Documentation

can_access_course()

core_tag_index_builder::can_access_course

(

$courseid

)

Checks if current user has access to the course.

This method calls global function can_access_course and caches results

Parameters

int

$courseid

Return values

bool

get_course()

core_tag_index_builder::get_course

(

$courseid

)

Retrieves a course record (only fields id,visible,fullname,shortname,cacherev).

This method is useful because it also caches results and preloads course context.

Parameters

int

$courseid

get_items()

core_tag_index_builder::get_items

(

)

Returns the filtered records from SQL query result.

This function can only be executed after $builder->has_item_that_needs_access_check() returns null

Return values

array

has_item_that_needs_access_check()

core_tag_index_builder::has_item_that_needs_access_check

(

)

Returns the first row from the SQL result that we don't know whether it is accessible by user or not.

This will return null when we have necessary number of accessible items to return in get_items()

After analyzing you may decide to mark not only this record but all similar as accessible or not accessible. For example, if you already call get_fast_modinfo() to check this item's accessibility, why not mark all items in the same course as accessible or not accessible.

Helpful methods: set_accessible() and walk()

Return values

null|object

set_accessible()

core_tag_index_builder::set_accessible	(		$identifier,
			$accessible = true )

Marks record or group of records as accessible (or not accessible)

Parameters

int | std_Class	$identifier	either record id of the item that needs to be set accessible
bool	$accessible	whether to mark as accessible or not accessible (default true)

walk()

core_tag_index_builder::walk

(

$callable

)

Walk through the array of items and call $callable for each of them.

Parameters

callable

$callable

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The documentation for this class was generated from the following file:

• tag/classes/index_builder.php