JsonObject sealed

sealed class JsonObject

Annotations: @immutable

An immutable, ordered JSON object (key-value map).

Keys are Strings and values are Json. Insertion order is preserved. Use the factory methods to construct instances and add, remove, mapValues, and filter to produce modified copies.

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;

isEmpty no setter

bool get isEmpty

Returns true if this object has no entries.

Implementation

bool get isEmpty;

isNotEmpty no setter

bool get isNotEmpty

Returns true if this object has at least one entry.

Implementation

bool get isNotEmpty => !isEmpty;

keys no setter

IList<String> get keys

The keys of this object in insertion order.

Implementation

IList<String> get keys;

nonEmpty no setter

bool get nonEmpty

Returns true if this object has at least one entry.

Implementation

bool get nonEmpty => !isEmpty;

runtimeType no setter inherited

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation

external Type get runtimeType;

size no setter

int get size

The number of entries in this object.

Implementation

int get size;

values no setter

IList<Json> get values

The values of this object in insertion order.

Implementation

IList<Json> get values;

Methods

add()

JsonObject add(String key, Json value)

Returns a copy with key set to value (overwrites if key exists).

Implementation

JsonObject add(String key, Json value);

contains()

bool contains(String key)

Returns true if key is present.

Implementation

bool contains(String key);

deepMerge()

JsonObject deepMerge(JsonObject that)

Recursively merges that into this object.

Fields present in both are merged recursively; fields only in this object are added to that.

Implementation

JsonObject deepMerge(JsonObject that) => toIList().foldLeft(
  that,
  (acc, kv) => that
      .get(kv.$1)
      .fold(
        () => acc.add(kv.$1, kv.$2),
        (r) => acc.add(kv.$1, kv.$2.deepMerge(r)),
      ),
);

filter()

JsonObject filter(bool Function(Record) p)

Returns a copy containing only the entries for which p returns true.

Implementation

JsonObject filter(Function1<(String, Json), bool> p) => JsonObject.fromIList(toIList().filter(p));

forEach()

void forEach(void Function(String key, Json value) f)

Iterates over all key-value pairs in insertion order.

Implementation

void forEach(void Function(String key, Json value) f);

get()

Option<Json> get(String key)

Returns Some with the value for key, or None if absent.

Implementation

Option<Json> get(String key);

getUnsafe()

Json getUnsafe(String key)

Returns the value for key, throwing if absent.

Implementation

Json getUnsafe(String key);

mapValues()

JsonObject mapValues(Json Function(Json) f)

Returns a copy with each value replaced by f(value).

Implementation

JsonObject mapValues(Function1<Json, Json> f);

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);

remove()

JsonObject remove(String key)

Returns a copy with key removed (no-op if key is absent).

Implementation

JsonObject remove(String key);

toIList()

IList<Record> toIList()

Returns the entries as an IList of (key, value) pairs in insertion order.

Implementation

IList<(String, Json)> toIList();

toJson()

Json toJson()

Wraps this object in a JObject.

Implementation

Json toJson() => Json.fromJsonObject(this);

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();

tryGet()

Json? tryGet(String key)

Returns the value for key, or null if absent. Avoids Option allocation.

Implementation

Json? tryGet(String key);

Operators

operator ==() inherited

bool operator ==(Object other)

The equality operator.

The default behavior for all Objects is to return true if and only if this object and other are the same object.

Override this method to specify a different equality relation on a class. The overriding method must still be an equivalence relation. That is, it must be:

• Total: It must return a boolean for all arguments. It should never throw.

• Reflexive: For all objects o, o == o must be true.

• Symmetric: For all objects o1 and o2, o1 == o2 and o2 == o1 must either both be true, or both be false.

• Transitive: For all objects o1, o2, and o3, if o1 == o2 and o2 == o3 are true, then o1 == o3 must be true.

The method should also be consistent over time, so whether two objects are equal should only change if at least one of the objects was modified.

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

Inherited from Object.

Implementation

external bool operator ==(Object other);

Static Properties

empty no setter

JsonObject get empty

An empty JsonObject.

Implementation

static JsonObject get empty => _LinkedHashMapJsonObject(LinkedHashMap());

Static Methods

fromIList()

JsonObject fromIList(IList<Record> fields)

Creates a JsonObject from an IList of (key, value) pairs.

Implementation

static JsonObject fromIList(IList<(String, Json)> fields) => fromIterable(fields.toList());

fromIterable()

JsonObject fromIterable(Iterable<Record> fields)

Creates a JsonObject from an Iterable of (key, value) pairs. Later entries with the same key overwrite earlier ones.

Implementation

static JsonObject fromIterable(Iterable<(String, Json)> fields) {
  final map = <String, Json>{};

  for (final (k, v) in fields) {
    map[k] = v;
  }

  return _LinkedHashMapJsonObject(map as LinkedHashMap<String, Json>);
}

fromMap()

JsonObject fromMap(Map<String, Json> fields)

Wraps an existing Map directly, avoiding repeated iteration.

Implementation

static JsonObject fromMap(Map<String, Json> fields) =>
    _LinkedHashMapJsonObject(LinkedHashMap.from(fields));