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[FEATURE] add foreach expression for arrays

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Gustry authored and nyalldawson committed Aug 16, 2018
1 parent 2d5499b commit 0a2062119104f3b0b3dccc2b2c5db5922523786e
@@ -0,0 +1,13 @@
{
"name": "array_foreach",
"type": "function",
"description": "Returns an array with the given expression evaluated on each item.",
"arguments": [
{"arg":"array","description":"an array"},
{"arg":"expression","description":"an expression to evaluate on each item. The variable `@element` will be replaced by the current value."}
],
"examples": [
{ "expression": "array_foreach(array('a','b','c'),upper(@element))", "returns":"array: 'A', 'B', 'C'"},
{ "expression": "array_foreach(array(1,2,3),@element + 10)", "returns":"array: 11, 12, 13"}
]
}
@@ -4729,6 +4729,7 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
<< new QgsStaticExpressionFunction( QStringLiteral( "raster_value" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "layer" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "band" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "point" ) ), fcnRasterValue, QStringLiteral( "Rasters" ) )

// functions for arrays
<< new QgsArrayForeachExpressionFunction()
<< new QgsStaticExpressionFunction( QStringLiteral( "array" ), -1, fcnArray, QStringLiteral( "Arrays" ), QString(), false, QSet<QString>(), false, QStringList(), true )
<< new QgsStaticExpressionFunction( QStringLiteral( "array_length" ), 1, fcnArrayLength, QStringLiteral( "Arrays" ) )
<< new QgsStaticExpressionFunction( QStringLiteral( "array_contains" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "array" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "value" ) ), fcnArrayContains, QStringLiteral( "Arrays" ) )
@@ -4774,6 +4775,93 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
return sFunctions;
}

QgsArrayForeachExpressionFunction::QgsArrayForeachExpressionFunction()
: QgsExpressionFunction( QStringLiteral( "array_foreach" ), 2, QCoreApplication::tr( "Arrays" ) )
{

}

bool QgsArrayForeachExpressionFunction::isStatic( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const
{
bool isStatic = false;

QgsExpressionNode::NodeList *args = node->args();

if ( args->count() < 2 )
return false;

if ( args->at( 0 )->isStatic( parent, context ) && args->at( 1 )->isStatic( parent, context ) )
{
isStatic = true;
}
return isStatic;
}

QVariant QgsArrayForeachExpressionFunction::run( QgsExpressionNode::NodeList *args, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node )
{
Q_UNUSED( node )
QVariantList result;

if ( args->count() < 2 )
// error
return result;

QVariantList array = args->at( 0 )->eval( parent, context ).toList();

QgsExpressionContext *subContext = const_cast<QgsExpressionContext *>( context );
if ( !context )
subContext = new QgsExpressionContext();

QgsExpressionContextScope *subScope = new QgsExpressionContextScope();
subContext->appendScope( subScope );

for ( QVariantList::const_iterator it = array.constBegin(); it != array.constEnd(); ++it )
{
subScope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "element" ), *it, true ) );
result << args->at( 1 )->eval( parent, subContext );
}

if ( !context )
delete subContext;

return result;
}

QVariant QgsArrayForeachExpressionFunction::func( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node )
{
// This is a dummy function, all the real handling is in run
Q_UNUSED( values )
Q_UNUSED( context )
Q_UNUSED( parent )
Q_UNUSED( node )

Q_ASSERT( false );
return QVariant();
}

bool QgsArrayForeachExpressionFunction::prepare( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const
{
QgsExpressionNode::NodeList *args = node->args();

if ( args->count() < 2 )
// error
return false;

args->at( 0 )->prepare( parent, context );

QgsExpressionContext subContext;
if ( context )
subContext = *context;

QgsExpressionContextScope *subScope = new QgsExpressionContextScope();
subScope->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "element" ), QVariant(), true ) );
subContext.appendScope( subScope );

args->at( 1 )->prepare( parent, &subContext );

return true;
}

QgsWithVariableExpressionFunction::QgsWithVariableExpressionFunction()
: QgsExpressionFunction( QStringLiteral( "with_variable" ), 3, QCoreApplication::tr( "General" ) )
{
@@ -498,6 +498,29 @@ class QgsStaticExpressionFunction : public QgsExpressionFunction
bool mIsStatic = false;
};

/**
* Handles the ``array_foreach(array, expression)`` expression function.
* It temporarily appends a new scope to the expression context.
*
* \ingroup core
* \note Not available in Python bindings
* \since QGIS 3.4
*/
class QgsArrayForeachExpressionFunction : public QgsExpressionFunction
{
public:
QgsArrayForeachExpressionFunction();

bool isStatic( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const override;

QVariant run( QgsExpressionNode::NodeList *args, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node ) override;

QVariant func( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent, const QgsExpressionNodeFunction *node ) override;

bool prepare( const QgsExpressionNodeFunction *node, QgsExpression *parent, const QgsExpressionContext *context ) const override;

};

/**
* Handles the ``with_variable(name, value, node)`` expression function.
* It temporarily appends a new scope to the expression context for all nested
@@ -2687,6 +2687,10 @@ class TestQgsExpression: public QObject
concatExpected << QStringLiteral( "a" ) << QStringLiteral( "b" ) << QStringLiteral( "c" );
QCOMPARE( QgsExpression( "array_cat(\"strings\", array('a', 'b'), array('c'))" ).evaluate( &context ), QVariant( concatExpected ) );

QVariantList foreachExpected;
foreachExpected << QStringLiteral( "ABC" ) << QStringLiteral( "HELLO" );
QCOMPARE( QgsExpression( "array_foreach(array('abc', 'hello'), upper(@element))" ).evaluate( &context ), QVariant( foreachExpected ) );

QCOMPARE( QgsExpression( "array_intersect(array('1', '2', '3', '4'), array('4', '0', '2', '5'))" ).evaluate( &context ), QVariant( true ) );
QCOMPARE( QgsExpression( "array_intersect(array('1', '2', '3', '4'), array('0', '5'))" ).evaluate( &context ), QVariant( false ) );

@@ -2766,6 +2770,10 @@ class TestQgsExpression: public QObject
QCOMPARE( QgsExpression( "array_slice(array(1,2,3,4,5),-2,-1) = array(4,5)" ).evaluate( &context ), QVariant( true ) );
QCOMPARE( QgsExpression( "array_slice(array(1,2,3,4,5),-1,-1) = array(5)" ).evaluate( &context ), QVariant( true ) );

QVariantList foreachExpected;
foreachExpected << 10 << 20 << 40;
QCOMPARE( QgsExpression( "array_foreach(array(1, 2, 4), @element * 10)" ).evaluate( &context ), QVariant( foreachExpected ) );

QgsExpression badArray( QStringLiteral( "array_get('not an array', 0)" ) );
QCOMPARE( badArray.evaluate( &context ), QVariant() );
QVERIFY( badArray.hasEvalError() );

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