Class (Set)

A non-linear data structure.

NOTE

The initial APIs of this module are supported since API version 12. Newly added APIs will be marked with a superscript to indicate their earliest API version.

This module can be imported only to ArkTS files (with the file name extension .ets).

This section uses the following to identify the use of generics:

T: type, which can be any of the sendable data types.

Decorator: @Sendable

Modules to Import

import { collections } from '@kit.ArkTS';

Properties

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Name	Type	Read Only	Optional	Description
size	number	Yes	No	Number of elements in a set.

constructor

constructor(values?: readonly T[]|null)

A constructor used to create an ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
values	readonly T[] \|null	No	Array or iterator object. The default value is null, indicating that an empty set is created.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error.
10200012	The ArkTS Set's constructor cannot be directly invoked.

Example

// Positive example 1:
const mySet = new collections.Set<number>();

// Positive example 2:
const mySet = new collections.Set<number>([1, 2, 3, 4, 5]);

// Negative example:
@Sendable
class SharedClass {
  constructor() {
  }
}

let sObj = new SharedClass();
const mySet1: collections.Set<number|SharedClass> = new collections.Set<number|SharedClass>([1, sObj]);
// Type arguments of generic "Sendable" type must be a "Sendable" data type (arkts-sendable-generic-types)
let obj = new Object();
const mySet2: collections.Set<number|SharedClass> = new collections.Set<number|Object>([1, obj]);

constructor

constructor(iterable: Iterable<T>)

A constructor used to create an ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
iterable	Iterable<T>	Yes	Object used to construct an ArkTS set.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error.
10200012	The ArkTS Set's constructor cannot be directly invoked.

Example

const mapper = new Map([
  ['1', 'a'],
  ['2', 'b'],
]);
let newSet = new collections.Set<string>(mapper.values());
console.info(newSet.has('a').toString()); // Expected output: true
console.info(newSet.has('b').toString()); // Expected output: true

entries

entries(): IterableIterator<[T, T]>

Returns a set iterator object that contains the key-value pair of each element in this ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
IterableIterator<[T, T]>	Returns a set iterator object that contains the key-value pair of each element in this ArkTS set.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200011	The entries method cannot be bound with non-sendable.
10200201	Concurrent modification error.

Example

const mySet = new collections.Set<number>([0, 1, 2, 3]);

const iterator = mySet.entries();
// Expected output: [0, 0]
console.info(iterator.next().value);
// Expected output: [1, 1]
console.info(iterator.next().value);

keys

keys(): IterableIterator<T>

Returns a set iterator object that contains the key of each element in this ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
IterableIterator<T>	Returns a set iterator object that contains the key of each element in this ArkTS set.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200011	The keys method cannot be bound with non-sendable.
10200201	Concurrent modification error.

Example

const mySet = new collections.Set<number>([0, 1, 2, 3]);

const iterator = mySet.keys();
// Expected output: 0
console.info(iterator.next().value);
// Expected output: 1
console.info(iterator.next().value);

values

values(): IterableIterator<T>

Returns a set iterator object that contains the value of each element in this ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
IterableIterator<T>	Returns a set iterator object that contains the value of each element in this ArkTS set.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200011	The values method cannot be bound with non-sendable.
10200201	Concurrent modification error.

Example

// Example 1:
const mySet = new collections.Set<number>([0, 1, 2, 3]);

const iterator = mySet.values();
// Expected output: 0
console.info(iterator.next().value);
// Expected output: 1
console.info(iterator.next().value);

// Example 2:
const mySet = new collections.Set<number>([0, 1, 2, 3]);

const valueIter = mySet.values();
for (let value of valueIter) {
    if (value % 2 == 0) {
        mySet.delete(value);
    }
}

// Expected output: 2
console.info("size:" + mySet.size);

clear

clear(): void

Removes all elements from this ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200011	The clear method cannot be bound with non-sendable.
10200201	Concurrent modification error.

Example

const mySet = new collections.Set<number>([0, 1]);
// Expected output: 2
console.info("size:" + mySet.size);
mySet.clear();
// Expected output: 0
console.info("size:" + mySet.size);

delete

delete(value: T): boolean

Deletes an element from this ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	T	Yes	Target value.

Return value

Type	Description
boolean	Operation result. The value true is returned if the key is deleted; otherwise, false is returned.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200011	The delete method cannot be bound with non-sendable.
10200201	Concurrent modification error.

Example

const mySet = new collections.Set<string>(["hello", "world"]);
// Expected result: true
console.info("result:" + mySet.delete("hello"));
// Expected result: false
console.info("result:" + mySet.has("hello"));
// Expected result: false
console.info("result:" + mySet.delete("hello"));

forEach

forEach(callbackFn: (value: T, value2: T, set: Set<T>) => void): void

Calls a callback function for each key-value pair in this ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
callbackFn	(value: T, value2: T, set: Set<T>) => void	Yes	Callback function to run for each key-value pair.

callbackFn parameters

Name	Type	Mandatory	Description
value	T	No	Value of the element that is currently traversed.
value2	T	No	Key of the element that is currently traversed.
set	Set<T>	No	Current set object.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error.
10200011	The forEach method cannot be bound with non-sendable.
10200201	Concurrent modification error.

Example

// Positive example:
new collections.Set<string>(['foo', 'bar', 'baz']).forEach((value1, value2, set) => {
  console.info(`s[${value1}] = ${value2}`);
});

// Negative example:
new collections.Set<string>(['foo', 'bar', 'baz']).forEach((value1, value2, set) => {
  // Throw exception `Concurrent modification error.`
  set.delete(value1);
});

has

has(value: T): boolean

Checks whether a value exists in this ArkTS set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	T	Yes	Target key.

Return value

Type	Description
boolean	Check result. The value true is returned if the value exists; otherwise, false is returned.

Error codes

For details about the error codes, see Universal Error Codes and Utils Error Codes.

ID	Error Message
401	Parameter error.
10200011	The has method cannot be bound with non-sendable.
10200201	Concurrent modification error.

Example

const mySet = new collections.Set<string>(["hello", "world"]);
// Expected output: true
console.info("result:" + mySet.has("hello"));
// Expected output: true
console.info("result:" + mySet.has("world"));

add

add(value: T): Set<T>

Checks whether a value exists in this ArkTS set, and if not, adds the value to the set.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Parameters

Name	Type	Mandatory	Description
value	T	Yes	Target value.

Return value

Type	Description
Set<T>	Set object.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200011	The add method cannot be bound with non-sendable.
10200201	Concurrent modification error.

Example

// Positive example:
const mySet: collections.Set<string> = new collections.Set<string>();
mySet.add("foo");

// Negative example:
let obj = new Object();
const mySet: collections.Set<Object> = new collections.Set<Object>();
// Type arguments of generic "Sendable" type must be a "Sendable" data type (arkts-sendable-generic-types)
mySet.add(obj);

[Symbol.iterator]

[Symbol.iterator](): IterableIterator<T>

Returns an iterator, each item of which is a JavaScript object.

NOTE

This API cannot be used in .ets files.

Atomic service API: This API can be used in atomic services since API version 12.

System capability: SystemCapability.Utils.Lang

Return value

Type	Description
IterableIterator<T>	Iterator obtained.

Error codes

For details about the error codes, see Utils Error Codes.

ID	Error Message
10200011	The Symbol.iterator method cannot be bound.

Example

let set = new collections.Set<number>([1, 2, 3, 4, 5]);

let val: Array<number> = Array.from(set.values());
for (let item of val) {
  console.info("value: " + item);
}