QGIS API Documentation
3.0.2-Girona (307d082)
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A store for object properties. More...
#include <qgsproperty.h>
Public Types | |
enum | Type { InvalidProperty, StaticProperty, FieldBasedProperty, ExpressionBasedProperty } |
Property types. More... | |
Public Member Functions | |
QgsProperty () | |
Constructor for a QgsAbstractProperty. More... | |
QgsProperty (const QgsProperty &other) | |
Copy constructor. More... | |
virtual | ~QgsProperty ()=default |
QString | asExpression () const |
Returns an expression string representing the state of the property, or an empty string if the property could not be converted to an expression. More... | |
bool | convertToTransformer () |
Attempts to convert an existing expression based property to a base expression with corresponding transformer. More... | |
QString | expressionString () const |
Returns the expression used for the property value. More... | |
QString | field () const |
Returns the current field name the property references. More... | |
bool | isActive () const |
Returns whether the property is currently active. More... | |
bool | loadVariant (const QVariant &property) |
Loads this property from a QVariantMap, wrapped in a QVariant. More... | |
operator bool () const | |
Returns true if the property is not an invalid type. More... | |
operator QVariant () const | |
Allows direct construction of QVariants from properties. More... | |
bool | operator!= (const QgsProperty &other) const |
QgsProperty & | operator= (const QgsProperty &other) |
bool | operator== (const QgsProperty &other) const |
bool | prepare (const QgsExpressionContext &context=QgsExpressionContext()) const |
Prepares the property against a specified expression context. More... | |
Type | propertyType () const |
Returns the property type. More... | |
QSet< QString > | referencedFields (const QgsExpressionContext &context=QgsExpressionContext()) const |
Returns the set of any fields referenced by the property for a specified expression context. More... | |
void | setActive (bool active) |
Sets whether the property is currently active. More... | |
void | setExpressionString (const QString &expression) |
Sets the expression to use for the property value. More... | |
void | setField (const QString &field) |
Sets the field name the property references. More... | |
void | setStaticValue (const QVariant &value) |
Sets the static value for the property. More... | |
void | setTransformer (QgsPropertyTransformer *transformer) |
Sets an optional transformer to use for manipulating the calculated values for the property. More... | |
QVariant | staticValue () const |
Returns the current static value for the property. More... | |
QVariant | toVariant () const |
Saves this property to a QVariantMap, wrapped in a QVariant. More... | |
const QgsPropertyTransformer * | transformer () const |
Returns the existing transformer used for manipulating the calculated values for the property, if set. More... | |
QVariant | value (const QgsExpressionContext &context, const QVariant &defaultValue=QVariant(), bool *ok=nullptr) const |
Calculates the current value of the property, including any transforms which are set for the property. More... | |
bool | valueAsBool (const QgsExpressionContext &context, bool defaultValue=false, bool *ok=nullptr) const |
Calculates the current value of the property and interprets it as an boolean. More... | |
QColor | valueAsColor (const QgsExpressionContext &context, const QColor &defaultColor=QColor(), bool *ok=nullptr) const |
Calculates the current value of the property and interprets it as a color. More... | |
double | valueAsDouble (const QgsExpressionContext &context, double defaultValue=0.0, bool *ok=nullptr) const |
Calculates the current value of the property and interprets it as a double. More... | |
int | valueAsInt (const QgsExpressionContext &context, int defaultValue=0, bool *ok=nullptr) const |
Calculates the current value of the property and interprets it as an integer. More... | |
QString | valueAsString (const QgsExpressionContext &context, const QString &defaultString=QString(), bool *ok=nullptr) const |
Calculates the current value of the property and interprets it as a string. More... | |
Static Public Member Functions | |
static QgsProperty | fromExpression (const QString &expression, bool isActive=true) |
Returns a new ExpressionBasedProperty created from the specified expression. More... | |
static QgsProperty | fromField (const QString &fieldName, bool isActive=true) |
Returns a new FieldBasedProperty created from the specified field name. More... | |
static QgsProperty | fromValue (const QVariant &value, bool isActive=true) |
Returns a new StaticProperty created from the specified value. More... | |
A store for object properties.
QgsProperty objects are used for storing properties for objects, which can then be transformed to a QVariant value by evaluating them against a supplied QgsExpressionContext. Multiple QgsProperty objects can be grouped using a QgsPropertyCollection for easier bulk storage, retrieval and evaluation.
QgsProperty objects are implicitly shared and can be inexpensively copied.
Definition at line 229 of file qgsproperty.h.
enum QgsProperty::Type |
Property types.
Definition at line 234 of file qgsproperty.h.
QgsProperty::QgsProperty | ( | ) |
Constructor for a QgsAbstractProperty.
The property will be set to an InvalidProperty type.
Definition at line 199 of file qgsproperty.cpp.
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virtualdefault |
QgsProperty::QgsProperty | ( | const QgsProperty & | other | ) |
Copy constructor.
Definition at line 228 of file qgsproperty.cpp.
QString QgsProperty::asExpression | ( | ) | const |
Returns an expression string representing the state of the property, or an empty string if the property could not be converted to an expression.
Definition at line 323 of file qgsproperty.cpp.
bool QgsProperty::convertToTransformer | ( | ) |
Attempts to convert an existing expression based property to a base expression with corresponding transformer.
Returns true if conversion was successful. Note that calling this method requires multiple parsing of expressions, so it should only be called in non-performance critical code.
Definition at line 747 of file qgsproperty.cpp.
QString QgsProperty::expressionString | ( | ) | const |
Returns the expression used for the property value.
If the property is not a ExpressionBasedProperty this will return an empty string.
Definition at line 314 of file qgsproperty.cpp.
QString QgsProperty::field | ( | ) | const |
Returns the current field name the property references.
If the property is not a FieldBasedProperty this will return an empty string.
Definition at line 292 of file qgsproperty.cpp.
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static |
Returns a new ExpressionBasedProperty created from the specified expression.
Definition at line 204 of file qgsproperty.cpp.
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static |
Returns a new FieldBasedProperty created from the specified field name.
Definition at line 212 of file qgsproperty.cpp.
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static |
Returns a new StaticProperty created from the specified value.
Definition at line 220 of file qgsproperty.cpp.
bool QgsProperty::isActive | ( | ) | const |
Returns whether the property is currently active.
Definition at line 258 of file qgsproperty.cpp.
bool QgsProperty::loadVariant | ( | const QVariant & | property | ) |
Loads this property from a QVariantMap, wrapped in a QVariant.
You can use QgsXmlUtils::readVariant to load it from an XML document.
Definition at line 674 of file qgsproperty.cpp.
QgsProperty::operator bool | ( | ) | const |
Returns true if the property is not an invalid type.
Definition at line 300 of file qgsproperty.cpp.
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inline |
Allows direct construction of QVariants from properties.
Definition at line 480 of file qgsproperty.h.
bool QgsProperty::operator!= | ( | const QgsProperty & | other | ) | const |
Definition at line 248 of file qgsproperty.cpp.
QgsProperty & QgsProperty::operator= | ( | const QgsProperty & | other | ) |
Definition at line 232 of file qgsproperty.cpp.
bool QgsProperty::operator== | ( | const QgsProperty & | other | ) | const |
Definition at line 238 of file qgsproperty.cpp.
bool QgsProperty::prepare | ( | const QgsExpressionContext & | context = QgsExpressionContext() | ) | const |
Prepares the property against a specified expression context.
Calling prepare before evaluating the property multiple times allows precalculation of expensive setup tasks such as parsing expressions. Returns true if preparation was successful.
Definition at line 347 of file qgsproperty.cpp.
QgsProperty::Type QgsProperty::propertyType | ( | ) | const |
Returns the property type.
Definition at line 253 of file qgsproperty.cpp.
QSet< QString > QgsProperty::referencedFields | ( | const QgsExpressionContext & | context = QgsExpressionContext() | ) | const |
Returns the set of any fields referenced by the property for a specified expression context.
Definition at line 389 of file qgsproperty.cpp.
void QgsProperty::setActive | ( | bool | active | ) |
Sets whether the property is currently active.
Definition at line 263 of file qgsproperty.cpp.
void QgsProperty::setExpressionString | ( | const QString & | expression | ) |
Sets the expression to use for the property value.
Calling this will transform the property into an ExpressionBasedProperty.
Definition at line 305 of file qgsproperty.cpp.
void QgsProperty::setField | ( | const QString & | field | ) |
Sets the field name the property references.
Calling this will transform the property into an FieldBasedProperty.
Definition at line 284 of file qgsproperty.cpp.
void QgsProperty::setStaticValue | ( | const QVariant & | value | ) |
Sets the static value for the property.
Calling this will transform the property into an StaticProperty.
Definition at line 269 of file qgsproperty.cpp.
void QgsProperty::setTransformer | ( | QgsPropertyTransformer * | transformer | ) |
Sets an optional transformer to use for manipulating the calculated values for the property.
transformer | transformer to install. Ownership is transferred to the property, and any existing transformer will be deleted. Set to null to remove an existing transformer. |
Definition at line 736 of file qgsproperty.cpp.
QVariant QgsProperty::staticValue | ( | ) | const |
Returns the current static value for the property.
If the property is not a StaticProperty this will return an invalid variant.
Definition at line 276 of file qgsproperty.cpp.
QVariant QgsProperty::toVariant | ( | ) | const |
Saves this property to a QVariantMap, wrapped in a QVariant.
You can use QgsXmlUtils::writeVariant to save it to an XML document.
Definition at line 636 of file qgsproperty.cpp.
const QgsPropertyTransformer * QgsProperty::transformer | ( | ) | const |
Returns the existing transformer used for manipulating the calculated values for the property, if set.
Definition at line 742 of file qgsproperty.cpp.
QVariant QgsProperty::value | ( | const QgsExpressionContext & | context, |
const QVariant & | defaultValue = QVariant() , |
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bool * | ok = nullptr |
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Calculates the current value of the property, including any transforms which are set for the property.
context | QgsExpressionContext to evaluate the property for. The variables and functions contained in the expression context can be used to alter the calculated value for the property, so that a property is able to respond to the current environment, layers and features within QGIS. |
defaultValue | default value to return if the property is not active or cannot be calculated |
ok | if specified, will be set to true if conversion was successful |
Definition at line 488 of file qgsproperty.cpp.
bool QgsProperty::valueAsBool | ( | const QgsExpressionContext & | context, |
bool | defaultValue = false , |
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bool * | ok = nullptr |
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Calculates the current value of the property and interprets it as an boolean.
context | QgsExpressionContext to evaluate the property for. |
defaultValue | default boolean to return if the property cannot be calculated as an boolean |
ok | if specified, will be set to true if conversion was successful |
Definition at line 620 of file qgsproperty.cpp.
QColor QgsProperty::valueAsColor | ( | const QgsExpressionContext & | context, |
const QColor & | defaultColor = QColor() , |
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bool * | ok = nullptr |
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) | const |
Calculates the current value of the property and interprets it as a color.
context | QgsExpressionContext to evaluate the property for. |
defaultColor | default color to return if the property cannot be calculated as a color |
ok | if specified, will be set to true if conversion was successful |
Definition at line 530 of file qgsproperty.cpp.
double QgsProperty::valueAsDouble | ( | const QgsExpressionContext & | context, |
double | defaultValue = 0.0 , |
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bool * | ok = nullptr |
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) | const |
Calculates the current value of the property and interprets it as a double.
context | QgsExpressionContext to evaluate the property for. |
defaultValue | default double to return if the property cannot be calculated as a double |
ok | if specified, will be set to true if conversion was successful |
Definition at line 561 of file qgsproperty.cpp.
int QgsProperty::valueAsInt | ( | const QgsExpressionContext & | context, |
int | defaultValue = 0 , |
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bool * | ok = nullptr |
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) | const |
Calculates the current value of the property and interprets it as an integer.
context | QgsExpressionContext to evaluate the property for. |
defaultValue | default integer to return if the property cannot be calculated as an integer |
ok | if specified, will be set to true if conversion was successful |
Definition at line 584 of file qgsproperty.cpp.
QString QgsProperty::valueAsString | ( | const QgsExpressionContext & | context, |
const QString & | defaultString = QString() , |
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bool * | ok = nullptr |
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) | const |
Calculates the current value of the property and interprets it as a string.
context | QgsExpressionContext to evaluate the property for. |
defaultString | default string to return if the property cannot be calculated as a string |
ok | if specified, will be set to true if conversion was successful |
Definition at line 511 of file qgsproperty.cpp.