Qore::HashKeyIterator Class Reference

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

Inheritance diagram for Qore::HashKeyIterator:

Public Member Methods
	constructor (hash< auto > h)
	Creates the hash iterator object. More...
	constructor ()
	Creates an empty hash iterator object. More...
	copy ()
	Creates a copy of the HashKeyIterator object, iterating the same object as the original and in the same position. More...
string	getValue ()
	returns the current key value or throws an INVALID-ITERATOR exception if the iterator is invalid 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...
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...

Detailed Description

This class an iterator class for hashes.

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

Example: HashKeyIterator basic usage

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

Note

• In general, the HashKeyIterator 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.

See also

HashKeyReverseIterator

Member Function Documentation

constructor() [1/2]

Qore::HashKeyIterator::constructor

(

)

Creates an empty hash iterator object.

Example:

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

constructor() [2/2]

Qore::HashKeyIterator::constructor

(

hash< auto >

h

)

Creates the hash iterator object.

Parameters

h	the hash to iterate

Example:

HashKeyIterator hi(h);

copy()

Qore::HashKeyIterator::copy

(

)

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

Example:

HashKeyIterator ni = i.copy();

getValue()

string Qore::HashKeyIterator::getValue ( )

virtual

returns the current key value or throws an INVALID-ITERATOR exception if the iterator is invalid

Returns

the current key value or throws an INVALID-ITERATOR exception if the iterator is invalid

Code Flags:

RET_VALUE_ONLY

Example:

foreach string key in (hash.keyIterator())
    printf("key: %s\n", key);

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

Reimplemented from Qore::HashIterator.