Solid::Predicate
#include <Solid/Predicate>
Public Types | |
enum | ComparisonOperator { Equals , Mask } |
enum | Type { PropertyCheck , Conjunction , Disjunction , InterfaceCheck } |
Static Public Member Functions | |
static Predicate | fromString (const QString &predicate) |
Detailed Description
This class implements predicates for devices.
A predicate is a logical condition that a given device can match or not. It's a constraint about the value a property must have in a given device interface, or any combination (conjunction, disjunction) of such constraints.
A predicate can be:
- a single comparison, or
- a conjunction ("AND") of exactly two predicates, or
- a disjunction ("OR") of exactly two predicates.
Since these can be nested, it is possible to express "a StorageVolume that is not ignored AND that StorageVolume contains a FileSystem AND that StorageVolume is removable". Since conjunctions use exactly two predicates (and this expression has three), square brackets are used to group the nested predicates when writing them out in full:
Predicates can be constructed programmatically by creating single comparisons with the Predicate constructor, and then building conjunctions with operator&
and disjunctions with operator|
.
Predicates can be constructed from a string by calling fromString()
which parses the given string and returns a predicate. If there are any errors in parsing the string, an empty predicate is returned; use isValid()
to detect whether that is the case.
The string language is described exactly in predicate_parser.y
, but boils down to:
- a single comparison is written as
<interface>.<property> == <value>
- a single bitmask check is written as
<interface>.<property> & <value>
- a conjunction is written as
[ <predicate> AND <predicate> ]
- a disjunction is written as
[ <predicate> OR <predicate> ]
Note the mandatory use of [
and ]
around conjunctions and disjunctions.
Member Enumeration Documentation
◆ ComparisonOperator
The comparison operator which can be used for matching within the predicate.
- Equals, the property and the value will match for strict equality
- Mask, the property and the value will match if the bitmasking is not null
Definition at line 75 of file predicate.h.
◆ Type
The predicate type which controls how the predicate is handled.
- PropertyCheck, the predicate contains a comparison that needs to be matched using a ComparisonOperator
- Conjunction, the two contained predicates need to be true for this predicate to be true
- Disjunction, either of the two contained predicates may be true for this predicate to be true
- InterfaceCheck, the device type is compared
Definition at line 85 of file predicate.h.
Constructor & Destructor Documentation
◆ Predicate() [1/6]
Solid::Predicate::Predicate | ( | ) |
Constructs an invalid predicate.
Definition at line 41 of file predicate.cpp.
◆ Predicate() [2/6]
Solid::Predicate::Predicate | ( | const Predicate & | other | ) |
Copy constructor.
- Parameters
-
other the predicate to copy
Definition at line 46 of file predicate.cpp.
◆ Predicate() [3/6]
Solid::Predicate::Predicate | ( | const DeviceInterface::Type & | ifaceType, |
const QString & | property, | ||
const QVariant & | value, | ||
ComparisonOperator | compOperator = Equals ) |
Constructs a predicate matching the value of a property in a given device interface.
- Parameters
-
ifaceType the device interface type the device must have property the property name of the device interface value the value the property must have to make the device match compOperator the operator to apply between the property and the value when matching
Definition at line 52 of file predicate.cpp.
◆ Predicate() [4/6]
Solid::Predicate::Predicate | ( | const QString & | ifaceName, |
const QString & | property, | ||
const QVariant & | value, | ||
ComparisonOperator | compOperator = Equals ) |
Constructs a predicate matching the value of a property in a given device interface.
- Parameters
-
ifaceName the name of the device interface the device must have property the property name of the device interface value the value the property must have to make the device match compOperator the operator to apply between the property and the value when matching
Definition at line 62 of file predicate.cpp.
◆ Predicate() [5/6]
|
explicit |
Constructs a predicate matching devices being of a particular device interface.
- Parameters
-
ifaceType the device interface the device must have
Definition at line 76 of file predicate.cpp.
◆ Predicate() [6/6]
|
explicit |
Constructs a predicate matching devices being of a particular device interface.
- Parameters
-
ifaceName the name of the device interface the device must have
Definition at line 84 of file predicate.cpp.
◆ ~Predicate()
Solid::Predicate::~Predicate | ( | ) |
Destroys a Predicate object.
Definition at line 96 of file predicate.cpp.
Member Function Documentation
◆ comparisonOperator()
Solid::Predicate::ComparisonOperator Solid::Predicate::comparisonOperator | ( | ) | const |
Retrieves the comparison operator used to compare a property's value.
- Since
- 4.4
- Note
- This is only valid for Conjunction and Disjunction types
- Returns
- the comparison operator used
Definition at line 334 of file predicate.cpp.
◆ firstOperand()
Solid::Predicate Solid::Predicate::firstOperand | ( | ) | const |
A smaller, inner predicate which is the first to appear and is compared with the second one.
- Since
- 4.4
- Note
- This is only valid for Conjunction and Disjunction types
- Returns
- The predicate used for the first operand
Definition at line 339 of file predicate.cpp.
◆ fromString()
|
static |
Converts a string to a predicate.
- Parameters
-
predicate the string to convert
- Returns
- a new valid predicate if the given string is syntactically correct, Predicate() otherwise
Definition at line 40 of file predicateparse.cpp.
◆ interfaceType()
Solid::DeviceInterface::Type Solid::Predicate::interfaceType | ( | ) | const |
Retrieves the interface type.
- Note
- This is only valid for InterfaceCheck and PropertyCheck types
- Since
- 4.4
- Returns
- a device interface type used by the predicate
Definition at line 319 of file predicate.cpp.
◆ isValid()
bool Solid::Predicate::isValid | ( | ) | const |
Indicates if the predicate is valid.
Predicate() is the only invalid predicate.
- Returns
- true if the predicate is valid, false otherwise
Definition at line 164 of file predicate.cpp.
◆ matches()
bool Solid::Predicate::matches | ( | const Device & | device | ) | const |
Checks if a device matches the predicate.
- Parameters
-
device the device to match against the predicate
- Returns
- true if the given device matches the predicate, false otherwise
Definition at line 169 of file predicate.cpp.
◆ matchingValue()
QVariant Solid::Predicate::matchingValue | ( | ) | const |
Retrieves the value used when comparing a devices property to see if it matches the predicate.
- Note
- This is only valid for the PropertyCheck type
- Since
- 4.4
- Returns
- the value used
Definition at line 329 of file predicate.cpp.
◆ operator&()
Solid::Predicate Solid::Predicate::operator& | ( | const Predicate & | other | ) |
'And' operator.
- Parameters
-
other the second operand
- Returns
- a new 'and' predicate having 'this' and 'other' as operands
Definition at line 128 of file predicate.cpp.
◆ operator&=()
Solid::Predicate & Solid::Predicate::operator&= | ( | const Predicate & | other | ) |
'AndEquals' operator.
- Parameters
-
other the second operand
- Returns
- assigns to 'this' a new 'and' predicate having 'this' and 'other' as operands
Definition at line 140 of file predicate.cpp.
◆ operator=()
Solid::Predicate & Solid::Predicate::operator= | ( | const Predicate & | other | ) |
Assignment operator.
- Parameters
-
other the predicate to assign
- Returns
- this predicate after having assigned 'other' to it
Definition at line 106 of file predicate.cpp.
◆ operator|()
Solid::Predicate Solid::Predicate::operator| | ( | const Predicate & | other | ) |
'Or' operator.
- Parameters
-
other the second operand
- Returns
- a new 'or' predicate having 'this' and 'other' as operands
Definition at line 146 of file predicate.cpp.
◆ operator|=()
Solid::Predicate & Solid::Predicate::operator|= | ( | const Predicate & | other | ) |
'OrEquals' operator.
- Parameters
-
other the second operand
- Returns
- assigns to 'this' a new 'or' predicate having 'this' and 'other' as operands
Definition at line 158 of file predicate.cpp.
◆ propertyName()
QString Solid::Predicate::propertyName | ( | ) | const |
Retrieves the property name used when retrieving the value to compare against.
- Note
- This is only valid for the PropertyCheck type
- Since
- 4.4
- Returns
- a property name
Definition at line 324 of file predicate.cpp.
◆ secondOperand()
Solid::Predicate Solid::Predicate::secondOperand | ( | ) | const |
A smaller, inner predicate which is the second to appear and is compared with the first one.
- Since
- 4.4
- Note
- This is only valid for Conjunction and Disjunction types
- Returns
- The predicate used for the second operand
Definition at line 347 of file predicate.cpp.
◆ toString()
QString Solid::Predicate::toString | ( | ) | const |
Converts the predicate to its string form.
- Returns
- a string representation of the predicate
Definition at line 255 of file predicate.cpp.
◆ type()
Solid::Predicate::Type Solid::Predicate::type | ( | ) | const |
Retrieves the predicate type, used to determine how to handle the predicate.
- Since
- 4.4
- Returns
- the predicate type
Definition at line 314 of file predicate.cpp.
◆ usedTypes()
QSet< Solid::DeviceInterface::Type > Solid::Predicate::usedTypes | ( | ) | const |
Retrieves the device interface types used in this predicate.
- Returns
- all the device interface types used in this predicate
Definition at line 234 of file predicate.cpp.
The documentation for this class was generated from the following files:
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