内容

公共函数
重实现公共函数
保护函数
详细描述

Q3PtrDict Class

The Q3PtrDict class is a template class that provides a dictionary based on void* keys. 更多...

头：	#include <Q3PtrDict>
继承：	Q3PtrCollection

所有成员列表，包括继承成员

公共函数

	Q3PtrDict (int size = 17)
	Q3PtrDict (const Q3PtrDict<type> & dict )
	~Q3PtrDict ()
type *	find (void * key ) const
void	insert (void * key , const type * item )
bool	isEmpty () const
bool	remove (void * key )
void	replace (void * key , const type * item )
void	resize (uint newsize )
uint	size () const
void	statistics () const
type *	take (void * key )
Q3PtrDict<type> &	operator= (const Q3PtrDict<type> & dict )
type *	operator[] (void * key ) const

重实现公共函数

virtual void	clear ()
virtual uint	count () const

4 公共函数继承自 Q3PtrCollection

保护函数

virtual QDataStream &	read (QDataStream & s , Q3PtrCollection::Item & item )
virtual QDataStream &	write (QDataStream & s , Q3PtrCollection::Item item ) const

2 保护函数继承自 Q3PtrCollection

详细描述

The Q3PtrDict class is a template class that provides a dictionary based on void* keys.

Q3PtrDict is implemented as a template class. Define a template instance Q3PtrDict <X> to create a dictionary that operates on pointers to X (X*).

A dictionary is a collection of key-value pairs. The key is a void* used for insertion, removal and lookup. The value is a pointer. Dictionaries provide very fast insertion and lookup.

范例：

Q3PtrDict<char> fields; // void* keys, char* values
QLineEdit *le1 = new QLineEdit( this );
le1->setText( "Simpson" );
QLineEdit *le2 = new QLineEdit( this );
le2->setText( "Homer" );
QLineEdit *le3 = new QLineEdit( this );
le3->setText( "45" );
fields.insert( le1, "Surname" );
fields.insert( le2, "Forename" );
fields.insert( le3, "Age" );
Q3PtrDictIterator<char> it( fields );
for( ; it.current(); ++it )
    cout << it.current() << endl;
cout << endl;
if ( fields[le1] ) // Prints "Surname: Simpson"
    cout << fields[le1] << ": " << le1->text() << endl;
if ( fields[le2] ) // Prints "Forename: Homer"
    cout << fields[le2] << ": " << le2->text() << endl;
fields.remove( le1 ); // Removes le1 from the dictionary
cout << le1->text() << endl; // Prints "Simpson"

In this example we use a dictionary to add an extra property (a char*) to the line edits we're using.

见 Q3Dict for full details, including the choice of dictionary size, and how deletions are handled.

另请参阅 Q3PtrDictIterator , Q3Dict , Q3AsciiDict ，和 Q3IntDict .

成员函数文档编制

Q3PtrDict:: Q3PtrDict ( int size = 17)

Constructs a dictionary using an internal hash array with the size size .

设置 size to a suitably large prime number (equal to or greater than the expected number of entries) makes the hash distribution better and improves lookup performance.

Q3PtrDict:: Q3PtrDict (const Q3PtrDict < type > & dict )

构造副本为 dict .

Each item in dict is inserted into this dictionary. Only the pointers are copied (shallow copy).

Q3PtrDict:: ~Q3PtrDict ()

Removes all items from the dictionary and destroys it.

All iterators that access this dictionary will be reset.

另请参阅 setAutoDelete ().

`[虚拟]` void Q3PtrDict:: clear ()

重实现自 Q3PtrCollection::clear ().

Removes all items from the dictionary.

The removed items are deleted if auto-deletion is enabled.

All dictionary iterators that access this dictionary will be reset.

另请参阅 remove (), take ()，和 setAutoDelete ().

`[虚拟]` uint Q3PtrDict:: count () const

重实现自 Q3PtrCollection::count ().

Returns the number of items in the dictionary.

另请参阅 isEmpty ().

type * Q3PtrDict:: find ( void * key ) const

Returns the item associated with key , or 0 if the key does not exist in the dictionary.

If there are two or more items with equal keys, then the most recently inserted item will be found.

Equivalent to operator[].

另请参阅 operator[] ().

void Q3PtrDict:: insert ( void * key , const type * item )

插入 key 采用 item into the dictionary.

Multiple items can have the same key, in which case only the last item will be accessible using operator[] ().

item 不可以为 0。

另请参阅 replace ().

bool Q3PtrDict:: isEmpty () const

Returns TRUE if the dictionary is empty; otherwise returns FALSE.

另请参阅 count ().

`[virtual protected]` QDataStream & Q3PtrDict:: read ( QDataStream & s , Q3PtrCollection::Item & item )

Reads a dictionary item from the stream s 并返回流引用。

The default implementation sets item 为 0。

另请参阅 write ().

bool Q3PtrDict:: remove ( void * key )

Removes the item associated with key from the dictionary. Returns TRUE if successful, i.e. if key is in the dictionary; otherwise returns FALSE.

If there are two or more items with equal keys, then the most recently inserted item will be removed.

The removed item is deleted if auto-deletion is enabled.

All dictionary iterators that refer to the removed item will be set to point to the next item in the dictionary traversal order.

另请参阅 take (), clear ()，和 setAutoDelete ().

void Q3PtrDict:: replace ( void * key , const type * item )

If the dictionary has key key , this key's item is replaced with item . If the dictionary doesn't contain key key , item is inserted into the dictionary using key key .

item 不可以为 0。

相当于

Q3PtrDict<ItemType> dict;
    ...
if ( dict.find( key ) )
    dict.remove( key );
dict.insert( key, item );

If there are two or more items with equal keys, then the most recently inserted item will be replaced.

另请参阅 insert ().

void Q3PtrDict:: resize ( uint newsize )

Changes the size of the hash table to newsize . The contents of the dictionary are preserved, but all iterators on the dictionary become invalid.

uint Q3PtrDict:: size () const

Returns the size of the internal hash table (as specified in the constructor).

另请参阅 count ().

void Q3PtrDict:: statistics () const

Debugging-only function that prints out the dictionary distribution using qDebug ().

type * Q3PtrDict:: take ( void * key )

Takes the item associated with key out of the dictionary without deleting it (even if auto-deletion is enabled).

If there are two or more items with equal keys, then the most recently inserted item will be removed.

Returns a pointer to the item taken out, or 0 if the key does not exist in the dictionary.

All dictionary iterators that refer to the taken item will be set to point to the next item in the dictionary traversal order.

另请参阅 remove (), clear ()，和 setAutoDelete ().

`[virtual protected]` QDataStream & Q3PtrDict:: write ( QDataStream & s , Q3PtrCollection::Item item ) const

Writes a dictionary item 到流 s 并返回流引用。

另请参阅 read ().

Q3PtrDict < type > & Q3PtrDict:: operator= (const Q3PtrDict < type > & dict )

赋值 dict to this dictionary and returns a reference to this dictionary.

This dictionary is first cleared and then each item in dict is inserted into the dictionary. Only the pointers are copied (shallow copy), unless newItem () has been reimplemented.

type * Q3PtrDict:: operator[] ( void * key ) const