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import {TemporalQuery} from 'js-joda/src/temporal/TemporalQuery.js'
public interface | source

TemporalQuery

Extends:

Enum → TemporalQuery

Strategy for querying a temporal object.

Queries are a key tool for extracting information from temporal objects. They exist to externalize the process of querying, permitting different approaches, as per the strategy design pattern. Examples might be a query that checks if the date is the day before February 29th in a leap year, or calculates the number of days to your next birthday.

The TemporalField interface provides another mechanism for querying temporal objects. That interface is limited to returning a long. By contrast, queries can return any type.

There are two equivalent ways of using a TemporalQuery. The first is to invoke the method on this interface directly. The second is to use TemporalAccessor#query:

  // these two lines are equivalent, but the second approach is recommended
  temporal = thisQuery.queryFrom(temporal);
  temporal = temporal.query(thisQuery);
It is recommended to use the second approach, query, as it is a lot clearer to read in code.

The most common implementations are method references, such as LocalDate::from and ZoneId::from. Further implementations are on TemporalQueries. Queries may also be defined by applications.

Specification for implementors

This interface places no restrictions on the mutability of implementations, however immutability is strongly recommended.

Method Summary

Public Methods
public

queryFrom(temporal: TemporalAccessor): *

Queries the specified temporal object.

Inherited Summary

From class Enum
public

equals(other: *): *

public

toJSON() use by JSON.stringify delegates to toString()

public

toString(): *

Public Methods

public queryFrom(temporal: TemporalAccessor): * source

Queries the specified temporal object.

This queries the specified temporal object to return an object using the logic encapsulated in the implementing class. Examples might be a query that checks if the date is the day before February 29th in a leap year, or calculates the number of days to your next birthday.

There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use TemporalAccessor#query:

  // these two lines are equivalent, but the second approach is recommended
  temporal = thisQuery.queryFrom(temporal);
  temporal = temporal.query(thisQuery);
It is recommended to use the second approach, query, as it is a lot clearer to read in code.

Specification for implementors

The implementation must take the input object and query it. The implementation defines the logic of the query and is responsible for documenting that logic. It may use any method on TemporalAccessor to determine the result. The input object must not be altered.

The input temporal object may be in a calendar system other than ISO. Implementations may choose to document compatibility with other calendar systems, or reject non-ISO temporal objects by querying the chronology (see TemporalQueries#chronology).

This method may be called from multiple threads in parallel. It must be thread-safe when invoked.

Params:

NameTypeAttributeDescription
temporal TemporalAccessor

the temporal object to query, not null

Return:

*

the queried value, may return null to indicate not found

Throw:

*

DateTimeException if unable to query

*

ArithmeticException if numeric overflow occurs