Qore::HashPairReverseIterator Class Reference

This class an iterator class for hashes. More...

#include <QC_HashPairReverseIterator.dox.h>

Inheritance diagram for Qore::HashPairReverseIterator:

Public Member Methods
	constructor (hash< auto > h)
	Creates the hash iterator object. More...
	constructor ()
	Creates an empty iterator object. More...
	copy ()
	Creates a copy of the HashPairReverseIterator object, iterating the same object as the original and in the same position. More...
hash< auto >	getValue ()
	returns a hash with the current key and value (a hash with 2 keys: "key" and "value") or throws an INVALID-ITERATOR exception if the iterator is invalid More...
Public Member Methods inherited from Qore::HashReverseIterator
	constructor (hash< auto > h)
	Creates the hash iterator object. More...
	constructor ()
	Creates an empty iterator object. More...
	copy ()
	Creates a copy of the HashReverseIterator object, iterating the same object as the original and in the same position. More...
bool	first ()
	returns True if on the last element of the hash More...
bool	last ()
	returns True if on the first element of the hash More...
bool	next ()
	Moves the current position to the previous element in the hash; returns False if there are no more elements; if the iterator is not pointing at a valid element before this call, the iterator will be positioned on the last element in the hash if the hash is not empty. More...
bool	prev ()
	Moves the current position to the next element in the hash; returns False if there are no more elements; if the iterator is not pointing at a valid element before this call, the iterator will be positioned on the first element in the hash if the hash is not empty. More...
Public Member Methods inherited from Qore::HashIterator
	constructor (hash< auto > h)
	Creates the hash iterator object. More...
	constructor ()
	Creates an empty hash iterator object. More...
	copy ()
	Creates a copy of the HashIterator object, iterating the same object as the original and in the same position. More...
bool	empty ()
	returns True if the hash is empty; False if not More...
bool	first ()
	returns True if on the first element of the hash More...
string	getKey ()
	returns the current key value or throws an INVALID-ITERATOR exception if the iterator is invalid More...
auto	getKeyValue ()
	returns the current value of the current hash key being iterated or throws an INVALID-ITERATOR exception if the iterator is invalid More...
auto	getValue ()
	returns the current key value or throws an INVALID-ITERATOR exception if the iterator is invalid More...
hash< auto >	getValuePair ()
	returns a hash with the current key and value (a hash with 2 keys: "key" and "value") or throws an INVALID-ITERATOR exception if the iterator is invalid More...
bool	last ()
	returns True if on the last element of the hash More...
bool	next ()
	Moves the current position to the next element in the hash; returns False if there are no more elements; if the iterator is not pointing at a valid element before this call, the iterator will be positioned on the first element in the hash if the hash is not empty. More...
bool	prev ()
	Moves the current position to the previous element in the hash; returns False if there are no more elements; if the iterator is not pointing at a valid element before this call, the iterator will be positioned on the last element in the hash if the hash is not empty. More...
	reset ()
	Reset the iterator instance to its initial state. More...
bool	valid ()
	returns True if the iterator is currently pointing at a valid element, False if not More...
abstract bool	prev ()
	Moves the current position to the previous element; returns False if there are no more elements. More...
abstract auto	getValue ()
	returns the current value More...
abstract bool	next ()
	Moves the current position to the next element; returns False if there are no more elements. More...
abstract bool	valid ()
	returns True if the iterator is currently pointing at a valid element, False if not More...
abstract bool	empty ()
	returns True if the object to iterate is empty; False if not More...
abstract bool	first ()
	returns True if on the first element More...
abstract bool	last ()
	returns True if on the last element More...

Detailed Description

This class an iterator class for hashes.

Call HashPairReverseIterator::next() to iterate through the hash in reverse order; do not use the iterator if HashPairReverseIterator::next() returns False. A hash can be iterated in reverse order by calling HashPairReverseIterator::prev() instead of HashPairReverseIterator::next()

Example: HashPairReverseIterator basic usage

hash<auto> data = {
    "key1" : 1,
    "key2" : 2,
    "key3" : 3,
};
 
HashPairReverseIterator it(data);
while (it.next()) {
    printf("iter: %n\n", it.getValue());
}
 
iter: hash: (key : "key3", value : 3)
iter: hash: (key : "key2", value : 2)
iter: hash: (key : "key1", value : 1)

Note

• In general, the HashPairReverseIterator class is not designed to be accessed from multiple threads; it was created without locking for fast and efficient use when used from a single thread. For methods that would be unsafe to use in another thread, any use of such methods in threads other than the thread where the constructor was called will cause an ITERATOR-THREAD-ERROR to be thrown.
• HashPairReverseIterator is functionally equivalent to HashPairIterator, but the effect of HashPairReverseIterator::next() and HashPairReverseIterator::prev() are the opposite of HashPairIterator::next() and HashPairIterator::prev(); that is HashPairReverseIterator::next() will iterate through the hash in reverse order, while HashPairReverseIterator::prev() iterates in forward order. Additionally the meanings of the return values for HashPairReverseIterator::first() and HashPairReverseIterator::last() are swapped in respect to HashPairIterator::first() and HashPairIterator::last().

See also

HashPairIterator

Member Function Documentation

constructor() [1/2]

Qore::HashPairReverseIterator::constructor

(

)

Creates an empty iterator object.

Example:

*hash<auto> h = get_hash_or_nothing();
HashPairReverseIterator hi(h);

constructor() [2/2]

Qore::HashPairReverseIterator::constructor

(

hash< auto >

h

)

Creates the hash iterator object.

Parameters

h	the hash to iterate

Example:

HashPairReverseIterator hi(h);

copy()

Qore::HashPairReverseIterator::copy

(

)

Creates a copy of the HashPairReverseIterator object, iterating the same object as the original and in the same position.

Example:

HashPairReverseIterator ni = i.copy();

getValue()

hash< auto > Qore::HashPairReverseIterator::getValue ( )

virtual

returns a hash with the current key and value (a hash with 2 keys: "key" and "value") or throws an INVALID-ITERATOR exception if the iterator is invalid

Returns

a hash with the current key and value (a hash with 2 keys: "key" and "value") or throws an INVALID-ITERATOR exception if the iterator is invalid

Code Flags:

RET_VALUE_ONLY

Example:

map printf("%s: %y\n", $1.key, $1.value), hash.pairIterator();

Exceptions

INVALID-ITERATOR	the iterator is not pointing at a valid element
ITERATOR-THREAD-ERROR	this exception is thrown if this method is called from any thread other than the thread that created the object

Since

Qore 0.8.6.2

Reimplemented from Qore::HashIterator.