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Function: copyRxSubject() ​

Call Signature ​

copyRxSubject<TCopy, TRxSource, T>(rxSource, rxCopy?, valueModifier?, defer?): SubjectLike<TCopy>

Defined in: packages/rx/src/copyRxSubject.ts:117

Function

copyRxSubject

Type Parameters ​

TCopy ​

TCopy

TRxSource ​

TRxSource = RxSourceType

T ​

T = UnwrapRxSourceValue<TRxSource>

Parameters ​

rxSource ​

TRxSource

RxJS source subject(s). If Array provied, value of rxCopy will also be an Array by default, unless a different type is provided by rxCopy or valueModifier.

rxCopy? ​

SubjectLike<TCopy>

(optional) RxJS copy/destination subject. If undefined, a new subject will be created. Value type will be inferred automatically based on rxCopy, valueModifier and rxSource. Default: new BehaviorSubject()

valueModifier? ​

ValueModifier<T, TCopy>

(optional) callback to modify the value (an thus type) before copying from rxSource. Accepts async functions. Function invocation errors will be gracefully ignored. PS: If the very first invokation returns IGNORE_UPDATE_SYMBOL, the value of rxCopy.value will be undefined. Args: newValue, previousValue, rxCopy

defer? ​

number

(optional) delay in milliseconds. Default: 100 if rxSource is an array, otherwise, 0.

Returns ​

SubjectLike<TCopy>

rxCopy

Examples ​

typescript
const rxNumber = new BehaviorSubject(1)
const rxEven = copyRxSubject(
    rxNumber,
    // If not provided, rxEven will be created and returned: `new BehaviorSubject<boolean>(false),`
    // Type will be inferred from `valueModifier` if available, otherwise, `rxNumber`.
    undefined,
    // whenever a new value is received from rxNumber, reduce it to the appropriate value for the rxEven.
    (newValue) => newValue % 2 === 0,
)
// subscribe to changes
// will immediately print false from the initial value of rxNumber
rxEven.subscribe(console.log)
rxNumber.next(2) // prints: true
rxNumber.next(3) // print: false

Automatically reduces to a single array with original values and their respective types

typescript
 const rxTheme = new BehaviorSubject<'dark' | 'lite'>('dark')
 const rxUserId = new BehaviorSubject('username')
 const rxUserSettings = copyRxSubject(
     [rxTheme, rxUser, 'my-fancy-app' ] as const
 )
 // subscribe to the subject with reduced array values
 rxUserSettings.subscribe(([theme, user, appName]) => {})
typescript
 const rxTheme = new BehaviorSubject<'dark' | 'lite'>('dark')
 const rxUserId = new BehaviorSubject('username')
 const rxUserSettings = copyRxSubject(
     [rxTheme, rxUserId] as const,
     // A new subject will be created from `valueModifier` to: `new BehaviorSubject<...>(...),`
     undefined,
     ([theme, userId]) => ({ theme, userId }),
     100, // delay before updating rxCopy
 )
 // save settings to local storage whenever any of the values changes
 rxUserSettings.subscribe(settings => localStorage.setItem(settings.userId, JSON.stringify(settings)))

Non-subjects will act as unobserved values to be included in the final value.

typescript
 const rxTheme = new BehaviorSubject<'dark' | 'lite'>('dark')
 const rxUser = new BehaviorSubject({ balance: 1000, currency: 'usd', userId: 'username' })
 const rxProfileProps = copyRxSubject(
     [rxTheme, rxUser, 'my-fancy-app' ] as const,
     // A new subject will be created from `valueModifier` to: `new BehaviorSubject<...>(...),`
     undefined,
     ([theme, userId, appName]) => ({ appName, theme, userId }),
     100, // delay before updating rxCopy
 )
 const userProfileView = (
     <RxSubjectView
         subject={rxProfileProps}
         render={props => <UserProfile {...props} />}
     />
 )

Call Signature ​

copyRxSubject<TCopy, TRxSource, T>(rxSource, rxCopy, valueModifier, defer?): SubjectLike<TCopy>

Defined in: packages/rx/src/copyRxSubject.ts:131

Overload for when TCopy doesn't extend T (modifier required)

Type Parameters ​

TCopy ​

TCopy

TRxSource ​

TRxSource = RxSourceType

T ​

T = UnwrapRxSourceValue<TRxSource>

Parameters ​

rxSource ​

TRxSource

rxCopy ​

undefined | SubjectLike<TCopy>

valueModifier ​

ValueModifier<T, TCopy>

Value of rxSource (T) and value of rxCopy (TCopy) are not the same, therefore, valueModifier is required to transform the value(s) of rxSource into value of rxCopy.

defer? ​

number

Returns ​

SubjectLike<TCopy>