InstanceMirror abstract

abstract class InstanceMirror implements ObjectMirror

An InstanceMirror reflects an instance of a Dart language object.

Implemented types

• ObjectMirror

Implementers

• ClosureMirror

Constructors

InstanceMirror()

InstanceMirror()

Properties

hashCode no setter inherited

int get hashCode

The hash code for this object.

A hash code is a single integer which represents the state of the object that affects operator == comparisons.

All objects have hash codes. The default hash code implemented by Object represents only the identity of the object, the same way as the default operator == implementation only considers objects equal if they are identical (see identityHashCode).

If operator == is overridden to use the object state instead, the hash code must also be changed to represent that state, otherwise the object cannot be used in hash based data structures like the default Set and Map implementations.

Hash codes must be the same for objects that are equal to each other according to operator ==. The hash code of an object should only change if the object changes in a way that affects equality. There are no further requirements for the hash codes. They need not be consistent between executions of the same program and there are no distribution guarantees.

Objects that are not equal are allowed to have the same hash code. It is even technically allowed that all instances have the same hash code, but if clashes happen too often, it may reduce the efficiency of hash-based data structures like HashSet or HashMap.

If a subclass overrides hashCode, it should override the operator == operator as well to maintain consistency.

Inherited from Object.

Implementation

external int get hashCode;

hasReflectee no setter

bool get hasReflectee

Whether reflectee will return the instance reflected by this mirror.

This will always be true in the local case (reflecting instances in the same isolate), but only true in the remote case if this mirror reflects a simple value.

A value is simple if one of the following holds:

• the value is null
• the value is of type num
• the value is of type bool
• the value is of type String

Implementation

bool get hasReflectee;

reflectee no setter

dynamic get reflectee

If the InstanceMirror reflects an instance it is meaningful to have a local reference to, we provide access to the actual instance here.

If you access reflectee when hasReflectee is false, an exception is thrown.

Implementation

dynamic get reflectee;

runtimeType no setter inherited

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation

external Type get runtimeType;

type no setter

ClassMirror get type

A mirror on the type of the reflectee.

Returns a mirror on the actual class of the reflectee. The class of the reflectee may differ from the object returned by invoking runtimeType on the reflectee.

Implementation

ClassMirror get type;

Methods

delegate() inherited

dynamic delegate(Invocation invocation)

Performs invocation on the reflectee of this ObjectMirror.

Equivalent to

if (invocation.isGetter) {
  return this.getField(invocation.memberName).reflectee;
} else if (invocation.isSetter) {
  return this.setField(invocation.memberName,
                       invocation.positionalArguments[0]).reflectee;
} else {
  return this.invoke(invocation.memberName,
                     invocation.positionalArguments,
                     invocation.namedArguments).reflectee;
}

Inherited from ObjectMirror.

Implementation

delegate(Invocation invocation);

getField() inherited

InstanceMirror getField(Symbol fieldName)

Invokes a getter and returns a mirror on the result.

The getter can be the implicit getter for a field or a user-defined getter method.

Let o be the object reflected by this mirror, let f be the simple name of the getter denoted by fieldName.

Then this method will perform the getter invocation o.f in a scope that has access to the private members of o (if o is a class or library) or the private members of the class of o (otherwise).

If this mirror is an InstanceMirror, and fieldName denotes an instance method on its reflectee, the result of the invocation is an instance mirror on a closure corresponding to that method.

If this mirror is a LibraryMirror, and fieldName denotes a top-level method in the corresponding library, the result of the invocation is an instance mirror on a closure corresponding to that method.

If this mirror is a ClassMirror, and fieldName denotes a static method in the corresponding class, the result of the invocation is an instance mirror on a closure corresponding to that method.

If the invocation returns a result r, this method returns the result of calling reflect(r).

If the invocation causes a compilation error, the effect is the same as if a non-reflective compilation error had been encountered.

If the invocation throws an exception e (that it does not catch), this method throws e.

Inherited from ObjectMirror.

Implementation

// TODO(ahe): Remove stuff about scope and private members. [fieldName] is a
// capability giving access to private members.
InstanceMirror getField(Symbol fieldName);

invoke() inherited

InstanceMirror invoke(
  Symbol memberName,
  List<dynamic> positionalArguments, [
  Map<Symbol, dynamic> namedArguments = const <Symbol, dynamic>{},
])

Invokes the named function and returns a mirror on the result.

Let o be the object reflected by this mirror, let f be the simple name of the member denoted by memberName, let a1, ..., an be the elements of positionalArguments, let k1, ..., km be the identifiers denoted by the elements of namedArguments.keys, and let v1, ..., vm be the elements of namedArguments.values. Then this method will perform the method invocation o.f(a1, ..., an, k1: v1, ..., km: vm) in a scope that has access to the private members of o (if o is a class or library) or the private members of the class of o (otherwise).

If the invocation returns a result r, this method returns the result of calling reflect(r).

If the invocation causes a compilation error the effect is the same as if a non-reflective compilation error had been encountered.

If the invocation throws an exception e (that it does not catch), this method throws e.

Inherited from ObjectMirror.

Implementation

InstanceMirror invoke(
  Symbol memberName,
  List<dynamic> positionalArguments, [
  Map<Symbol, dynamic> namedArguments = const <Symbol, dynamic>{},
]);

noSuchMethod() inherited

dynamic noSuchMethod(Invocation invocation)

Invoked when a nonexistent method or property is accessed.

A dynamic member invocation can attempt to call a member which doesn't exist on the receiving object. Example:

dynamic object = 1;
object.add(42); // Statically allowed, run-time error

This invalid code will invoke the noSuchMethod method of the integer 1 with an Invocation representing the .add(42) call and arguments (which then throws).

Classes can override noSuchMethod to provide custom behavior for such invalid dynamic invocations.

A class with a non-default noSuchMethod invocation can also omit implementations for members of its interface. Example:

class MockList<T> implements List<T> {
  noSuchMethod(Invocation invocation) {
    log(invocation);
    super.noSuchMethod(invocation); // Will throw.
  }
}
void main() {
  MockList().add(42);
}

This code has no compile-time warnings or errors even though the MockList class has no concrete implementation of any of the List interface methods. Calls to List methods are forwarded to noSuchMethod, so this code will log an invocation similar to Invocation.method(#add, [42]) and then throw.

If a value is returned from noSuchMethod, it becomes the result of the original invocation. If the value is not of a type that can be returned by the original invocation, a type error occurs at the invocation.

The default behavior is to throw a NoSuchMethodError.

Inherited from Object.

Implementation

@pragma("vm:entry-point")
@pragma("wasm:entry-point")
external dynamic noSuchMethod(Invocation invocation);

setField() inherited

InstanceMirror setField(Symbol fieldName, dynamic value)

Invokes a setter and returns a mirror on the result.

The setter may be either the implicit setter for a non-final field or a user-defined setter method.

Let o be the object reflected by this mirror, let f be the simple name of the getter denoted by fieldName, and let a be the object bound to value.

Then this method will perform the setter invocation o.f = a in a scope that has access to the private members of o (if o is a class or library) or the private members of the class of o (otherwise).

If the invocation returns a result r, this method returns the result of calling reflect(value).

If the invocation causes a compilation error, the effect is the same as if a non-reflective compilation error had been encountered.

If the invocation throws an exception e (that it does not catch) this method throws e.

Inherited from ObjectMirror.

Implementation

InstanceMirror setField(Symbol fieldName, dynamic value);

toString() inherited

String toString()

A string representation of this object.

Some classes have a default textual representation, often paired with a static parse function (like int.parse). These classes will provide the textual representation as their string representation.

Other classes have no meaningful textual representation that a program will care about. Such classes will typically override toString to provide useful information when inspecting the object, mainly for debugging or logging.

Inherited from Object.

Implementation

external String toString();

Operators

operator ==() override

bool operator ==(Object other)

Whether this mirror is equal to other.

The equality holds if and only if

1. other is a mirror of the same kind, and

2. either

a. hasReflectee is true and so is identical(reflectee, other.reflectee), or

b. the remote objects reflected by this mirror and by other are identical.

Implementation

bool operator ==(Object other);