ExpressionEvaluator class

Handles evaluation of expressions

The default ExpressionEvaluator handles all expressions except member expressions. To create an ExpressionEvaluator that handles member expressions, set a list of MemberAccessor instances to the memberAccessors argument of the constructor.

For example:

var evaluator = ExpressionEvaluator(memberAccessors: MemberAccessor<Person>({ 'firstname': (v)=>v.firstname, 'lastname': (v)=>v.lastname, 'address': (v)=>v.address }), MemberAccessor<Address>({ 'street': (v)=>v.street, 'locality': (v)=>v.locality, }), );

The MemberAccessor.mapAccessor can be used to access Map items with member access syntax.

An async ExpressionEvaluator can be created with the ExpressionEvaluator.async constructor. An async expression evaluator can handle operands and arguments that are streams or futures and will apply the expression on each value of those streams or futures. The result is always a stream.

For example:

var evaluator = ExpressionEvaluator.async();

var expression = Expression.parse('x > 70');

var r = evaluator.eval(expression, {'x': Stream.fromIterable(50, 80)});

r.forEach(print); // prints false and true

Constructors

ExpressionEvaluator.new({List<MemberAccessor> memberAccessors = const []})

const

ExpressionEvaluator.async({List<MemberAccessor> memberAccessors})

const

factory

Properties

hashCode → int

The hash code for this object.

no setter, inherited

memberAccessors → List<MemberAccessor>

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

eval(Expression expression, Map<String, dynamic> context, {void onValueAssigned(String key, dynamic value)?}) → dynamic

evalBinaryExpression(BinaryExpression expression, Map<String, dynamic> context, {void onValueAssigned(String key, dynamic value)?}) → dynamic

evalCallExpression(CallExpression expression, Map<String, dynamic> context) → dynamic

evalConditionalExpression(ConditionalExpression expression, Map<String, dynamic> context) → dynamic

evalIndexExpression(IndexExpression expression, Map<String, dynamic> context, {bool nullable = false}) → dynamic

evalLiteral(Literal literal, Map<String, dynamic> context) → dynamic

evalMemberExpression(MemberExpression expression, Map<String, dynamic> context, {bool nullable = false}) → dynamic

evalThis(ThisExpression expression, Map<String, dynamic> context) → dynamic

evalUnaryExpression(UnaryExpression expression, Map<String, dynamic> context) → dynamic

evalVariable(Variable variable, Map<String, dynamic> context) → dynamic

getMember(dynamic obj, String member, {bool nullable = false}) → dynamic

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited