Class: QgsAbstractValidityCheck¶
- class qgis.core.QgsAbstractValidityCheck¶
Bases:
sip.wrapper
Abstract base class for individual validity checks.
Validity checks represent objects which can run a test using a
QgsValidityCheckContext
, and return the results of the check viaQgsValidityCheckResult
objects.Checks can be used for many different use cases, e.g. validating a layout’s contents before allowing an export to occur, or validating the contents of a Processing model (and warning if required plugin based providers are not available or if compulsory algorithm parameters have not been populated).
Subclasses must indicate the type of check they represent via the
checkType()
method. When checks are performed, all the registered checks with a matching check type are performed sequentially. The check type also dictates the subclass of theQgsValidityCheckContext
which is given to the subclass’ runCheck method.Checks must be registered in the application’s
QgsValidityCheckRegistry
, which is accessible viaQgsApplication.validityCheckRegistry()
.See also
New in version 3.6:
Methods
Returns the type of the check.
Creates a new instance of the check and returns it.
Returns the unique ID of the check.
Prepares the check for execution, and returns
True
if the check can be run.Runs the check and returns a list of results.
Attributes
- class Type¶
Bases:
int
- TypeLayoutCheck = 0¶
- TypeUserCheck = 10000¶
- checkType(self) int ¶
Returns the type of the check.
- Return type
int
- create(self) QgsAbstractValidityCheck ¶
Creates a new instance of the check and returns it.
- Return type
- id(self) str ¶
Returns the unique ID of the check.
This is a non-translated, non-user visible string identifying the check.
- Return type
str
- prepareCheck(self, context: QgsValidityCheckContext, feedback: QgsFeedback) bool ¶
Prepares the check for execution, and returns
True
if the check can be run.This method is always called from the main thread, and subclasses can implement it to do preparatory steps which are not thread safe (e.g. obtaining feature sources from vector layers). It is followed by a call to
runCheck()
, which may be performed in a background thread.Individual calls to
prepareCheck()
/runCheck()
are run on a new instance of the check (seecreate()
), so subclasses can safely store state from theprepareCheck()
method ready for the subsequentrunCheck()
method.The
context
argument gives the wider in which the check is being run.- Parameters
context (QgsValidityCheckContext) –
feedback (QgsFeedback) –
- Return type
bool
- runCheck(self, context: QgsValidityCheckContext, feedback: QgsFeedback) List[QgsValidityCheckResult] ¶
Runs the check and returns a list of results. If the check is “passed” and no warnings or errors are generated, then an empty list should be returned.
This method may be called in a background thread, so subclasses should take care to ensure that only thread-safe methods are used. It is always preceded by a call to
prepareCheck()
.If a check needs to perform non-thread-safe tests, these should be implemented within
prepareCheck()
and stored in the subclass instance to be returned by this method.The
context
argument gives the wider in which the check is being run.- Parameters
context (QgsValidityCheckContext) –
feedback (QgsFeedback) –
- Return type
List[QgsValidityCheckResult]