CustomMatcher class Null safety

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)));
Inheritance

Constructors

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

Properties

hashCode → int
The hash code for this object.
read-onlyinherited
runtimeType → Type
A representation of the runtime type of the object.
read-onlyinherited

Methods

describe(Description description) → Description
Builds a textual description of the matcher.
override
describeMismatch(Object? item, Description mismatchDescription, Map matchState, bool verbose) → Description
Builds a textual description of a specific mismatch.
override
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.
override
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed.
inherited
toString() → String
A string representation of this object.
inherited

Operators

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