qvaluevector.3qt

linux下GUI编程工具qt的在线连接帮助手册

'\" t
.TH QValueVector 3qt "11 October 2001" "Trolltech AS" \" -*- nroff -*-
.\" Copyright 1992-2001 Trolltech AS.  All rights reserved.  See the
.\" license file included in the distribution for a complete license
.\" statement.
.\"
.ad l
.nh
.SH NAME
QValueVector \- Value-based template class that provides a dynamic array
.PP
\fC#include <qvaluevector.h>\fR
.PP
.SS "Public Members"
.in +1c
.ti -1c
.BI "typedef T \fBvalue_type\fR"
.br
.ti -1c
.BI "typedef value_type * \fBpointer\fR"
.br
.ti -1c
.BI "typedef const value_type * \fBconst_pointer\fR"
.br
.ti -1c
.BI "typedef value_type * \fBiterator\fR"
.br
.ti -1c
.BI "typedef const value_type * \fBconst_iterator\fR"
.br
.ti -1c
.BI "typedef value_type & \fBreference\fR"
.br
.ti -1c
.BI "typedef const value_type & \fBconst_reference\fR"
.br
.ti -1c
.BI "typedef size_t \fBsize_type\fR"
.br
.ti -1c
.BI "typedef ptrdiff_t \fBdifference_type\fR"
.br
.ti -1c
.BI "\fBQValueVector\fR ()"
.br
.ti -1c
.BI "\fBQValueVector\fR ( const QValueVector<T> & v )"
.br
.ti -1c
.BI "\fBQValueVector\fR ( size_type n, const T & val = T ( ) )"
.br
.ti -1c
.BI "\fBQValueVector\fR ( std::vector<T> & v )"
.br
.ti -1c
.BI "\fB~QValueVector\fR ()"
.br
.ti -1c
.BI "QValueVector<T> & \fBoperator=\fR ( const QValueVector<T> & v )"
.br
.ti -1c
.BI "QValueVector<T> & \fBoperator=\fR ( const std::vector<T> & v )"
.br
.ti -1c
.BI "size_type \fBsize\fR () const"
.br
.ti -1c
.BI "bool \fBempty\fR () const"
.br
.ti -1c
.BI "size_type \fBcapacity\fR () const"
.br
.ti -1c
.BI "iterator \fBbegin\fR ()"
.br
.ti -1c
.BI "const_iterator \fBbegin\fR () const"
.br
.ti -1c
.BI "iterator \fBend\fR ()"
.br
.ti -1c
.BI "const_iterator \fBend\fR () const"
.br
.ti -1c
.BI "reference \fBat\fR ( size_type i, bool * ok = 0 )"
.br
.ti -1c
.BI "const_reference \fBat\fR ( size_type i, bool * ok = 0 ) const"
.br
.ti -1c
.BI "reference \fBoperator[]\fR ( size_type i )"
.br
.ti -1c
.BI "const_reference \fBoperator[]\fR ( size_type i ) const"
.br
.ti -1c
.BI "reference \fBfront\fR ()"
.br
.ti -1c
.BI "const_reference \fBfront\fR () const"
.br
.ti -1c
.BI "reference \fBback\fR ()"
.br
.ti -1c
.BI "const_reference \fBback\fR () const"
.br
.ti -1c
.BI "void \fBpush_back\fR ( const T & x )"
.br
.ti -1c
.BI "void \fBpop_back\fR ()"
.br
.ti -1c
.BI "iterator \fBinsert\fR ( iterator pos, const T & x )"
.br
.ti -1c
.BI "iterator \fBinsert\fR ( iterator pos, size_type n, const T & x )"
.br
.ti -1c
.BI "void \fBreserve\fR ( size_type n )"
.br
.ti -1c
.BI "void \fBresize\fR ( size_type n, const T & val = T ( ) )"
.br
.ti -1c
.BI "void \fBclear\fR ()"
.br
.ti -1c
.BI "iterator \fBerase\fR ( iterator pos )"
.br
.ti -1c
.BI "iterator \fBerase\fR ( iterator first, iterator last )"
.br
.ti -1c
.BI "bool \fBoperator==\fR ( const QValueVector<T> & x )"
.br
.in -1c
.SS "Protected Members"
.in +1c
.ti -1c
.BI "void \fBdetach\fR ()"
.br
.in -1c
.SH DESCRIPTION
The QValueVector class is a value-based template class that provides a dynamic array.
.PP
QValueVector is a Qt implementation of an STL-like vector container. It can be used in your application if the standard \fCvector\fR is not available. QValueVector is part of the Qt Template Library.
.PP
QValueVector<T> defines a template instance to create a vector of values that all have the class T. Please note that QValueVector does not store pointers to the members of the vector; it holds a copy of every member. QValueVector is said to be value based; in contrast, QPtrList and QDict are pointer based.
.PP
QValueVector contains and manages a collection of objects of type T and provides random access iterators that allow the contained objects to be addressed. QValueVector owns the contained elements. For more relaxed ownership semantics, see QPtrCollection and friends which are pointer-based containers.
.PP
QValueVector provides good performance if you append or remove elements from the end of the vector. If you insert or remove elements from anywhere but the end, performance is very bad. The reason for this is that elements will need to be copied into new positions.
.PP
Some classes cannot be used within a QValueVector - for example, all classes derived from QObject and thus all classes that implement widgets. Only values can be used in a QValueVector. To qualify as a value the class must provide:
.TP
A copy constructor
.TP
An assignment operator
.TP
A default constructor, i.e., a constructor that does not take any arguments.
.PP
Note that C++ defaults to field-by-field assignment operators and copy constructors if no explicit version is supplied. In many cases this is sufficient.
.PP
QValueVector uses an STL-like syntax to manipulate and address the objects it contains. See this document for more information.
.PP
Example:
.PP
.nf
.br
    #include <qvaluevector.h>
.br
    #include <qstring.h>
.br
    #include <stdio.h>
.br
.br
    class Employee
.br
    {
.br
    public:
.br
        Employee(): s(0) {}
.br
        Employee( const QString& name, int salary )
.br
            : n(name), s(salary)
.br
        {}
.br
.br
        QString     name()   const              { return n; }
.br
        int         salary() const              { return s; }
.br
        void        setSalary( int salary )     { s = salary; }
.br
    private:
.br
        QString     n;
.br
        int         s;
.br
    };
.br
.br
    int main()
.br
    {
.br
        typedef QValueVector<Employee> EmployeeVector;
.br
        EmployeeVector vec( 4 );        // vector of 4 Employees
.br
.br
        vec[0] = Employee("Bill", 50000);
.br
        vec[1] = Employee("Steve",80000);
.br
        vec[2] = Employee("Ron",  60000);
.br
.br
        Employee joe( "Joe", 50000 );
.br
        vec.push_back( joe );
.br
        joe.setSalary( 4000 );
.br
.br
.br
        EmployeeVector::iterator it;
.br
        for( it = vec.begin(); it != vec.end(); ++it )
.br
            printf( "%s earns %d\\n", (*it).name().latin1(), (*it).salary() );
.br
.br
        return 0;
.br
    }
.br
.fi
.PP
Program output:
.PP
.nf
.br
        Bill earns 50000
.br
        Steve earns 80000
.br
        Ron earns 60000
.br
        Joe earns 50000
.br
.fi
.PP
As you can see, the latest changes to Joe's salary did not affect the value in the vector because the vector created a copy of Joe's entry.
.PP