CustomMatcher class

A useful utility class for implementing other matchers through inheritance. Derived classes should call the base constructor with a feature name and description, and an instance matcher, and should implement the featureValueOf abstract method.

The feature description will typically describe the item and the feature, while the feature name will just name the feature. For example, we may have a Widget class where each Widget has a price; we could make a CustomMatcher that can make assertions about prices with:

class HasPrice extends CustomMatcher {
  HasPrice(matcher) : super("Widget with price that is", "price", matcher);
  featureValueOf(actual) => (actual as Widget).price;

and then use this for example like:

expect(inventoryItem, HasPrice(greaterThan(0)));


CustomMatcher(String _featureDescription, String _featureName, Object? valueOrMatcher)


hashCode int
The hash code for this object.
no setterinherited
runtimeType Type
A representation of the runtime type of the object.
no setterinherited


describe(Description description) Description
Builds a textual description of the matcher.
describeMismatch(Object? item, Description mismatchDescription, Map matchState, bool verbose) Description
Builds a textual description of a specific mismatch.
featureValueOf(dynamic actual) Object?
Override this to extract the interesting feature.
matches(Object? item, Map matchState) bool
Does the matching of the actual vs expected values.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
toString() String
A string representation of this object.


operator ==(Object other) bool
The equality operator.