Solid::Predicate Class
class Solid::PredicateThis class implements predicates for devices. More...
| Header: | #include <Solid/Predicate> |
| CMake: | find_package(KF6 REQUIRED COMPONENTS Solid)target_link_libraries(mytarget PRIVATE KF6::Solid) |
Public Types
| enum | ComparisonOperator { Equals, Mask } |
| enum | Type { PropertyCheck, Conjunction, Disjunction, InterfaceCheck } |
Public Functions
| Predicate() | |
| Predicate(const QString &ifaceName) | |
| Predicate(const Solid::DeviceInterface::Type &ifaceType) | |
| Predicate(const QString &ifaceName, const QString &property, const QVariant &value, Solid::Predicate::ComparisonOperator compOperator = Equals) | |
| Predicate(const Solid::DeviceInterface::Type &ifaceType, const QString &property, const QVariant &value, Solid::Predicate::ComparisonOperator compOperator = Equals) | |
(since 4.4) Solid::Predicate::ComparisonOperator | comparisonOperator() const |
(since 4.4) Solid::Predicate | firstOperand() const |
(since 4.4) Solid::DeviceInterface::Type | interfaceType() const |
| bool | isValid() const |
| bool | matches(const Solid::Device &device) const |
(since 4.4) QVariant | matchingValue() const |
(since 4.4) QString | propertyName() const |
(since 4.4) Solid::Predicate | secondOperand() const |
| QString | toString() const |
(since 4.4) Solid::Predicate::Type | type() const |
| QSet<Solid::DeviceInterface::Type> | usedTypes() const |
| Solid::Predicate | operator&(const Solid::Predicate &other) |
| Solid::Predicate & | operator&=(const Solid::Predicate &other) |
| Solid::Predicate | operator|(const Solid::Predicate &other) |
| Solid::Predicate & | operator|=(const Solid::Predicate &other) |
Static Public Members
| Solid::Predicate | fromString(const QString &predicate) |
Detailed Description
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:
[ [ StorageVolume.ignored == false AND StorageVolume.usage == 'FileSystem' ] AND StorageVolume.removable == true ]
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 Type Documentation
enum Predicate::ComparisonOperator
The comparison operator which can be used for matching within the predicate.
| Constant | Value | Description |
|---|---|---|
Solid::Predicate::Equals | 0 | the property and the value will match for strict equality |
Solid::Predicate::Mask | 1 | the property and the value will match if the bitmasking is not null |
enum Predicate::Type
The predicate type which controls how the predicate is handled
| Constant | Value | Description |
|---|---|---|
Solid::Predicate::PropertyCheck | 0 | the predicate contains a comparison that needs to be matched using a ComparisonOperator |
Solid::Predicate::Conjunction | 1 | the two contained predicates need to be true for this predicate to be true |
Solid::Predicate::Disjunction | 2 | either of the two contained predicates may be true for this predicate to be true |
Solid::Predicate::InterfaceCheck | 3 | the device type is compared |
Member Function Documentation
Predicate::Predicate()
Constructs an invalid predicate.
[explicit] Predicate::Predicate(const QString &ifaceName)
Constructs a predicate matching devices being of a particular device interface
ifaceName the name of the device interface the device must have
[explicit] Predicate::Predicate(const Solid::DeviceInterface::Type &ifaceType)
Constructs a predicate matching devices being of a particular device interface
ifaceType the device interface the device must have
Predicate::Predicate(const QString &ifaceName, const QString &property, const QVariant &value, Solid::Predicate::ComparisonOperator compOperator = Equals)
Constructs a predicate matching the value of a property in a given device interface.
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
Predicate::Predicate(const Solid::DeviceInterface::Type &ifaceType, const QString &property, const QVariant &value, Solid::Predicate::ComparisonOperator compOperator = Equals)
Constructs a predicate matching the value of a property in a given device interface.
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
[since 4.4] Solid::Predicate::ComparisonOperator Predicate::comparisonOperator() const
Retrieves the comparison operator used to compare a property's value
Note: This is only valid for Conjunction and Disjunction types Returns the comparison operator used
This function was introduced in 4.4.
[since 4.4] Solid::Predicate Predicate::firstOperand() const
A smaller, inner predicate which is the first to appear and is compared with the second one
Note: This is only valid for Conjunction and Disjunction types Returns The predicate used for the first operand
This function was introduced in 4.4.
[static] Solid::Predicate Predicate::fromString(const QString &predicate)
Converts a string to a predicate.
predicate the string to convert
Returns a new valid predicate if the given string is syntactically correct, Predicate() otherwise
[since 4.4] Solid::DeviceInterface::Type Predicate::interfaceType() const
Retrieves the interface type.
Note: This is only valid for InterfaceCheck and PropertyCheck types Returns a device interface type used by the predicate
This function was introduced in 4.4.
bool Predicate::isValid() const
Indicates if the predicate is valid.
Predicate() is the only invalid predicate.
Returns true if the predicate is valid, false otherwise
bool Predicate::matches(const Solid::Device &device) const
Checks if a device matches the predicate.
device the device to match against the predicate
Returns true if the given device matches the predicate, false otherwise
[since 4.4] QVariant 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 Returns the value used
This function was introduced in 4.4.
[since 4.4] QString Predicate::propertyName() const
Retrieves the property name used when retrieving the value to compare against
Note: This is only valid for the PropertyCheck type Returns a property name
This function was introduced in 4.4.
[since 4.4] Solid::Predicate Predicate::secondOperand() const
A smaller, inner predicate which is the second to appear and is compared with the first one
Note: This is only valid for Conjunction and Disjunction types Returns The predicate used for the second operand
This function was introduced in 4.4.
QString Predicate::toString() const
Converts the predicate to its string form.
Returns a string representation of the predicate
[since 4.4] Solid::Predicate::Type Predicate::type() const
Retrieves the predicate type, used to determine how to handle the predicate
Returns the predicate type
This function was introduced in 4.4.
QSet<Solid::DeviceInterface::Type> Predicate::usedTypes() const
Retrieves the device interface types used in this predicate.
Returns all the device interface types used in this predicate
Solid::Predicate Predicate::operator&(const Solid::Predicate &other)
'And' operator.
other the second operand
Returns a new 'and' predicate having 'this' and 'other' as operands
Solid::Predicate &Predicate::operator&=(const Solid::Predicate &other)
'AndEquals' operator.
other the second operand
Assigns to 'this' a new 'and' predicate having 'this' and 'other' as operands
Solid::Predicate Predicate::operator|(const Solid::Predicate &other)
'Or' operator.
other the second operand
Returns a new 'or' predicate having 'this' and 'other' as operands
Solid::Predicate &Predicate::operator|=(const Solid::Predicate &other)
'OrEquals' operator.
other the second operand
Assigns to 'this' a new 'or' predicate having 'this' and 'other' as operands