[FEATURE] ascii function for expressions

Returns the unicode code associated with the first character of a string
qgis · Apr 19, 2020 · d6829fe · d6829fe
1 parent 9a6b0f5
commit d6829fe
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diff --git a/resources/function_help/json/ascii b/resources/function_help/json/ascii
@@ -0,0 +1,7 @@
+{
+  "name": "ascii",
+  "type": "function",
+  "description": "Returns the unicode code associated with the first character of a string.",
+  "arguments": [ {"arg":"string","description":"the string to convert to unicode code"}],
+  "examples": [ { "expression":"ascii('Q')", "returns":"81"} ]
+}
diff --git a/src/core/expression/qgsexpressionfunction.cpp b/src/core/expression/qgsexpressionfunction.cpp
@@ -1187,6 +1187,19 @@ static QVariant fcnChar( const QVariantList &values, const QgsExpressionContext
   return QVariant( QString( character ) );
 }
 
+static QVariant fcnAscii( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
+{
+  QString value = QgsExpressionUtils::getStringValue( values.at( 0 ), parent );
+
+  if ( value.isEmpty() )
+  {
+    return QVariant();
+  }
+
+  int res = value.at( 0 ).unicode();
+  return QVariant( res );
+}
+
 static QVariant fcnWordwrap( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent, const QgsExpressionNodeFunction * )
 {
   if ( values.length() == 2 || values.length() == 3 )
@@ -5579,6 +5592,7 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
         << new QgsStaticExpressionFunction( QStringLiteral( "hamming_distance" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "string1" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "string2" ) ), fcnHamming, QStringLiteral( "Fuzzy Matching" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "soundex" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "string" ) ), fcnSoundex, QStringLiteral( "Fuzzy Matching" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "char" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "code" ) ), fcnChar, QStringLiteral( "String" ) )
+        << new QgsStaticExpressionFunction( QStringLiteral( "ascii" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "string" ) ), fcnAscii, QStringLiteral( "String" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "wordwrap" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "text" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "length" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "delimiter" ), true, "" ), fcnWordwrap, QStringLiteral( "String" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "length" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "text" ), true, "" ), fcnLength, QStringList() << QStringLiteral( "String" ) << QStringLiteral( "GeometryGroup" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "replace" ), -1, fcnReplace, QStringLiteral( "String" ) )

diff --git a/tests/src/core/testqgsexpression.cpp b/tests/src/core/testqgsexpression.cpp
@@ -1231,6 +1231,9 @@ class TestQgsExpression: public QObject
       QTest::newRow( "trim" ) << "trim('   Test String ')" << false << QVariant( "Test String" );
       QTest::newRow( "trim empty string" ) << "trim('')" << false << QVariant( "" );
       QTest::newRow( "char" ) << "char(81)" << false << QVariant( "Q" );
+      QTest::newRow( "ascii single letter" ) << "ascii('Q')" << false << QVariant( 81 );
+      QTest::newRow( "ascii word" ) << "ascii('QGIS')" << false << QVariant( 81 );
+      QTest::newRow( "ascii empty" ) << "ascii('')" << false << QVariant();
       QTest::newRow( "wordwrap" ) << "wordwrap('university of qgis',13)" << false << QVariant( "university of\nqgis" );
       QTest::newRow( "wordwrap with custom delimiter" ) << "wordwrap('university of qgis',13,' ')" << false << QVariant( "university of\nqgis" );
       QTest::newRow( "wordwrap with negative length" ) << "wordwrap('university of qgis',-3)" << false << QVariant( "university\nof qgis" );