C/C++ – Page 2 – 0x2B|~0x2B

Basic Usage of Boost MultiIndex Containers

Posted on 2015-12-28 by gonwan — No Comments ↓

Just take a simple note here.
The Boost Multi-index Containers Library provides a class template named multi_index_container which enables the construction of containers maintaining one or more indices with different sorting and access semantics.

#include <string>
#include <ostream>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/tag.hpp>
#include <boost/lambda/lambda.hpp>
using namespace std;
using namespace boost::multi_index;


struct auth
{
    string m_name;
    string m_pass;
    auth(const string &name, const string &pass)
        : m_name(name), m_pass(pass) { }
    bool operator<(const auth &o) const { return m_name < o.m_name; }
    friend ostream &operator<<(ostream &os, const auth &a) { os << "(" << a.m_name << ", " << a.m_pass << ")"; return os; }
};

struct employee
{
    int m_id;
    auth m_auth;
    int m_hire;
    int m_resign;
    employee(int id, const string &name, const string &pass, int hire, int resign)
        : m_id(id), m_auth(name, pass), m_hire(hire), m_resign(resign) { }
    bool operator<(const employee &o) const { return m_id < o.m_id; }
    friend ostream &operator<<(ostream &os, const employee &e) { os << "(" << e.m_id << ", " << e.m_auth << ", " << e.m_hire << ", " << e.m_resign << ")"; return os; }
};


struct auth_t { };

struct change_resign {
    int m_resign;
    change_resign(int r) : m_resign(r) { }
    void operator()(employee &e) { e.m_resign = m_resign; }
};

typedef multi_index_container<
    employee,
    indexed_by<
        /* sort by employee::operator< */
        ordered_unique<identity<employee> >,
        /* sort by less<int> on m_hire */
        ordered_non_unique<member<employee, int, &employee::m_hire> >,
        /* sort by less<auth> on m_auth */
        ordered_non_unique<tag<auth_t>, member<employee, auth, &employee::m_auth> >
    >
> employee_set;

int main()
{
    employee_set es;
    es.insert(employee(1, "555", "555pass", 2012, 0));
    es.insert(employee(2, "444", "444pass", 2011, 0));
    es.insert(employee(3, "333", "333pass", 2013, 0));
    es.insert(employee(4, "222", "222pass", 2015, 0));
    es.insert(employee(5, "555", "555pass", 2014, 0)); /* dup */
    typedef employee_set::nth_index<1>::type hire_index_t;
    typedef employee_set::index<auth_t>::type auth_index_t;
    cout << "Get a view to index #1 (m_hire).." << endl;
    hire_index_t &hire_index = es.get<1>();
    std::copy(hire_index.begin(), hire_index.end(), ostream_iterator<employee>(cout, "\n"));
    cout << "Get a view to index tag auth_t (m_auth).." << endl;
    const auth_index_t &auth_index = es.get<auth_t>();
    std::copy(auth_index.begin(), auth_index.end(), ostream_iterator<employee>(cout, "\n"));
    cout << "Find.." << endl;
    hire_index_t::iterator it = hire_index.find(2015);
#if 0
    employee t = *it;
    t.m_resign = 2048;
    hire_index.replace(it, t);
#else
    hire_index.modify_key(it, boost::lambda::_1=1111);
    int old_resign = it->m_resign;
    hire_index.modify(it, change_resign(2048), change_resign(old_resign));
#endif
    cout << (*it) << endl;
    cout << "Find all.." << endl;
    pair<auth_index_t::const_iterator, auth_index_t::const_iterator> pr = auth_index.equal_range(auth("555", ""));
    std::copy(pr.first, pr.second, ostream_iterator<employee>(cout, "\n"));
    return 0;
}

#include <string>

#include <ostream>

#include <boost/multi_index_container.hpp>

#include <boost/multi_index/ordered_index.hpp>

#include <boost/multi_index/identity.hpp>

#include <boost/multi_index/member.hpp>

#include <boost/multi_index/tag.hpp>

#include <boost/lambda/lambda.hpp>

using namespace std;

using namespace boost::multi_index;

struct auth

{

string m_name;

string m_pass;

auth(const string &name, const string &pass)

: m_name(name), m_pass(pass) { }

bool operator<(const auth &o) const { return m_name < o.m_name; }

friend ostream &operator<<(ostream &os, const auth &a) { os << "(" << a.m_name << ", " << a.m_pass << ")"; return os; }

};

struct employee

{

int m_id;

auth m_auth;

int m_hire;

int m_resign;

employee(int id, const string &name, const string &pass, int hire, int resign)

: m_id(id), m_auth(name, pass), m_hire(hire), m_resign(resign) { }

bool operator<(const employee &o) const { return m_id < o.m_id; }

friend ostream &operator<<(ostream &os, const employee &e) { os << "(" << e.m_id << ", " << e.m_auth << ", " << e.m_hire << ", " << e.m_resign << ")"; return os; }

};

struct auth_t { };

struct change_resign {

int m_resign;

change_resign(int r) : m_resign(r) { }

void operator()(employee &e) { e.m_resign = m_resign; }

};

typedef multi_index_container<

employee,

indexed_by<

/* sort by employee::operator< */

ordered_unique<identity<employee> >,

/* sort by less<int> on m_hire */

ordered_non_unique<member<employee, int, &employee::m_hire> >,

/* sort by less<auth> on m_auth */

ordered_non_unique<tag<auth_t>, member<employee, auth, &employee::m_auth> >

> employee_set;

int main()

{

employee_set es;

es.insert(employee(1, "555", "555pass", 2012, 0));

es.insert(employee(2, "444", "444pass", 2011, 0));

es.insert(employee(3, "333", "333pass", 2013, 0));

es.insert(employee(4, "222", "222pass", 2015, 0));

es.insert(employee(5, "555", "555pass", 2014, 0)); /* dup */

typedef employee_set::nth_index<1>::type hire_index_t;

typedef employee_set::index<auth_t>::type auth_index_t;

cout << "Get a view to index #1 (m_hire).." << endl;

hire_index_t &hire_index = es.get<1>();

std::copy(hire_index.begin(), hire_index.end(), ostream_iterator<employee>(cout, "\n"));

cout << "Get a view to index tag auth_t (m_auth).." << endl;

const auth_index_t &auth_index = es.get<auth_t>();

std::copy(auth_index.begin(), auth_index.end(), ostream_iterator<employee>(cout, "\n"));

cout << "Find.." << endl;

hire_index_t::iterator it = hire_index.find(2015);

#if 0

employee t = *it;

t.m_resign = 2048;

hire_index.replace(it, t);

#else

hire_index.modify_key(it, boost::lambda::_1=1111);

int old_resign = it->m_resign;

hire_index.modify(it, change_resign(2048), change_resign(old_resign));

#endif

cout << (*it) << endl;

cout << "Find all.." << endl;

pair<auth_index_t::const_iterator, auth_index_t::const_iterator> pr = auth_index.equal_range(auth("555", ""));

std::copy(pr.first, pr.second, ostream_iterator<employee>(cout, "\n"));

return 0;

}

Output:

Get a view to index #1 (m_hire)..
(2, (444, 444pass), 2011, 0)
(1, (555, 555pass), 2012, 0)
(3, (333, 333pass), 2013, 0)
(5, (555, 555pass), 2014, 0)
(4, (222, 222pass), 2015, 0)
Get a view to index tag auth_t (m_auth)..
(4, (222, 222pass), 2015, 0)
(3, (333, 333pass), 2013, 0)
(2, (444, 444pass), 2011, 0)
(1, (555, 555pass), 2012, 0)
(5, (555, 555pass), 2014, 0)
Find..
(4, (222, 222pass), 1111, 2048)
Find all..
(1, (555, 555pass), 2012, 0)
(5, (555, 555pass), 2014, 0)

Get a view to index #1 (m_hire)..

(2, (444, 444pass), 2011, 0)

(1, (555, 555pass), 2012, 0)

(3, (333, 333pass), 2013, 0)

(5, (555, 555pass), 2014, 0)

(4, (222, 222pass), 2015, 0)

Get a view to index tag auth_t (m_auth)..

(4, (222, 222pass), 2015, 0)

(3, (333, 333pass), 2013, 0)

(2, (444, 444pass), 2011, 0)

(1, (555, 555pass), 2012, 0)

(5, (555, 555pass), 2014, 0)

Find..

(4, (222, 222pass), 1111, 2048)

Find all..

(1, (555, 555pass), 2012, 0)

(5, (555, 555pass), 2014, 0)

To use with pointer values, only limited change needed as highlighted:

#include <string>
#include <ostream>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/identity.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/tag.hpp>
#include <boost/lambda/lambda.hpp>
using namespace std;
using namespace boost::multi_index;


struct auth
{
    string m_name;
    string m_pass;
    auth(const string &name, const string &pass)
        : m_name(name), m_pass(pass) { }
    bool operator<(const auth &o) const { return m_name < o.m_name; }
    friend ostream &operator<<(ostream &os, const auth &a) { os << "(" << a.m_name << ", " << a.m_pass << ")"; return os; }
};

struct employee
{
    int m_id;
    auth m_auth;
    int m_hire;
    int m_resign;
    employee(int id, const string &name, const string &pass, int hire, int resign)
        : m_id(id), m_auth(name, pass), m_hire(hire), m_resign(resign) { }
    bool operator<(const employee &o) const { return m_id < o.m_id; }
    friend ostream &operator<<(ostream &os, const employee *e) { os << "(" << e->m_id << ", " << e->m_auth << ", " << e->m_hire << ", " << e->m_resign << ")"; return os; }
};


struct auth_t { };

struct change_resign {
    int m_resign;
    change_resign(int r) : m_resign(r) { }
    void operator()(employee *e) { e->m_resign = m_resign; }
};

typedef multi_index_container<
    employee *,
    indexed_by<
        /* sort by employee::operator< */
        ordered_unique<identity<employee> >,
        /* sort by less<int> on m_hire */
        ordered_non_unique<member<employee, int, &employee::m_hire> >,
        /* sort by less<auth> on m_auth */
        ordered_non_unique<tag<auth_t>, member<employee, auth, &employee::m_auth> >
    >
> employee_set;

int main()
{
    employee_set es;
    es.insert(new employee(1, "555", "555pass", 2012, 0));
    es.insert(new employee(2, "444", "444pass", 2011, 0));
    es.insert(new employee(3, "333", "333pass", 2013, 0));
    es.insert(new employee(4, "222", "222pass", 2015, 0));
    es.insert(new employee(5, "555", "555pass", 2014, 0)); /* dup */
    typedef employee_set::nth_index<1>::type hire_index_t;
    typedef employee_set::index<auth_t>::type auth_index_t;
    cout << "Get a view to index #1 (m_hire).." << endl;
    hire_index_t &hire_index = es.get<1>();
    std::copy(hire_index.begin(), hire_index.end(), ostream_iterator<employee *>(cout, "\n"));
    cout << "Get a view to index tag auth_t (m_auth).." << endl;
    const auth_index_t &auth_index = es.get<auth_t>();
    std::copy(auth_index.begin(), auth_index.end(), ostream_iterator<employee *>(cout, "\n"));
    cout << "Find.." << endl;
    hire_index_t::iterator it = hire_index.find(2015);
#if 0
    employee *t = *it;
    t->m_auth.m_name = "888";
    /* must use replace() to notify changes in indexed fields */
    hire_index.replace(it, t);
#else
    hire_index.modify_key(it, boost::lambda::_1=1111);
    int old_resign = (*it)->m_resign;
    hire_index.modify(it, change_resign(2048), change_resign(old_resign));
#endif
    cout << (*it) << endl;
    cout << "Find all.." << endl;
    pair<auth_index_t::const_iterator, auth_index_t::const_iterator> pr = auth_index.equal_range(auth("555", ""));
    std::copy(pr.first, pr.second, ostream_iterator<employee *>(cout, "\n"));
    /* clear */
    for (employee_set::const_iterator it = es.begin(); it != es.end(); ++it) {
        delete *it;
    }
    employee_set().swap(es);
    return 0;
}

#include <string>

#include <ostream>

#include <boost/multi_index_container.hpp>

#include <boost/multi_index/ordered_index.hpp>

#include <boost/multi_index/identity.hpp>

#include <boost/multi_index/member.hpp>

#include <boost/multi_index/tag.hpp>

#include <boost/lambda/lambda.hpp>

using namespace std;

using namespace boost::multi_index;

struct auth

{

string m_name;

string m_pass;

auth(const string &name, const string &pass)

: m_name(name), m_pass(pass) { }

bool operator<(const auth &o) const { return m_name < o.m_name; }

friend ostream &operator<<(ostream &os, const auth &a) { os << "(" << a.m_name << ", " << a.m_pass << ")"; return os; }

};

struct employee

{

int m_id;

auth m_auth;

int m_hire;

int m_resign;

employee(int id, const string &name, const string &pass, int hire, int resign)

: m_id(id), m_auth(name, pass), m_hire(hire), m_resign(resign) { }

bool operator<(const employee &o) const { return m_id < o.m_id; }

friend ostream &operator<<(ostream &os, const employee *e) { os << "(" << e->m_id << ", " << e->m_auth << ", " << e->m_hire << ", " << e->m_resign << ")"; return os; }

};

struct auth_t { };

struct change_resign {

int m_resign;

change_resign(int r) : m_resign(r) { }

void operator()(employee *e) { e->m_resign = m_resign; }

};

typedef multi_index_container<

employee *,

indexed_by<

/* sort by employee::operator< */

ordered_unique<identity<employee> >,

/* sort by less<int> on m_hire */

ordered_non_unique<member<employee, int, &employee::m_hire> >,

/* sort by less<auth> on m_auth */

ordered_non_unique<tag<auth_t>, member<employee, auth, &employee::m_auth> >

> employee_set;

int main()

{

employee_set es;

es.insert(new employee(1, "555", "555pass", 2012, 0));

es.insert(new employee(2, "444", "444pass", 2011, 0));

es.insert(new employee(3, "333", "333pass", 2013, 0));

es.insert(new employee(4, "222", "222pass", 2015, 0));

es.insert(new employee(5, "555", "555pass", 2014, 0)); /* dup */

typedef employee_set::nth_index<1>::type hire_index_t;

typedef employee_set::index<auth_t>::type auth_index_t;

cout << "Get a view to index #1 (m_hire).." << endl;

hire_index_t &hire_index = es.get<1>();

std::copy(hire_index.begin(), hire_index.end(), ostream_iterator<employee *>(cout, "\n"));

cout << "Get a view to index tag auth_t (m_auth).." << endl;

const auth_index_t &auth_index = es.get<auth_t>();

std::copy(auth_index.begin(), auth_index.end(), ostream_iterator<employee *>(cout, "\n"));

cout << "Find.." << endl;

hire_index_t::iterator it = hire_index.find(2015);

#if 0

employee *t = *it;

t->m_auth.m_name = "888";

/* must use replace() to notify changes in indexed fields */

hire_index.replace(it, t);

#else

hire_index.modify_key(it, boost::lambda::_1=1111);

int old_resign = (*it)->m_resign;

hire_index.modify(it, change_resign(2048), change_resign(old_resign));

#endif

cout << (*it) << endl;

cout << "Find all.." << endl;

pair<auth_index_t::const_iterator, auth_index_t::const_iterator> pr = auth_index.equal_range(auth("555", ""));

std::copy(pr.first, pr.second, ostream_iterator<employee *>(cout, "\n"));

/* clear */

for (employee_set::const_iterator it = es.begin(); it != es.end(); ++it) {

delete *it;

}

employee_set().swap(es);

return 0;

}

Database Access Layer in C++

Posted on 2015-04-15 by gonwan — No Comments ↓

We have JDBC in Java… and SOCI in C++… Well, it’s not so easy as it should be. To build with cmake:

# mkdir ../build
# cd ../build
# set ORACLE_HOME=C:\oraclexe\app\oracle\product\10.2.0\server
# cmake -G "Visual Studio 9 2008" -DMYSQL_INCLUDE_DIR="C:\Program Files\MySQL\MySQL Server 5.5\include" -DMYSQL_LIBRARIES="C:\Program Files\MySQL\MySQL Server 5.5\lib\libmysql.lib" ../soci-3.2.3

# mkdir ../build

# cd ../build

# set ORACLE_HOME=C:\oraclexe\app\oracle\product\10.2.0\server

# cmake -G "Visual Studio 9 2008" -DMYSQL_INCLUDE_DIR="C:\Program Files\MySQL\MySQL Server 5.5\include" -DMYSQL_LIBRARIES="C:\Program Files\MySQL\MySQL Server 5.5\lib\libmysql.lib" ../soci-3.2.3

The documents seem outdated, many options do not work. Just managed to figure out from the *.cmake source files. You can also download the oracle instant client SDK, and re-arrange the directory structure for build.

Code snippet I extracted from its unit tests:

#include "soci.h"
#include "soci-mysql.h"
//#include "soci-oracle.h"
#include <ctime>
#include <string>
#include <iostream>
#include <sstream>
using namespace std;

int main()
{
    try {
        soci::session sql(soci::mysql, "host=192.168.1.101 db=mysql user=root password=111111");
        //soci::session sql(soci::oracle, "service=192.168.1.102/ORCL user=sys password=111111");
        soci::row v;
        /* comma operator is overloaded here.. */
        soci::statement st = (sql.prepare << "SELECT * FROM user", into(v));
        //soci::statement st = (sql.prepare << "SELECT * FROM SYS.USER$", into(v));
        st.execute(true);  /* with data exchange */
        unsigned int num_fields = v.size();
        cout << "fields: " << num_fields << endl;
        num_fields = (num_fields <= 9) ? num_fields : 9;
        unsigned long num_rows = (unsigned long)st.get_affected_rows();
        cout << "rows: " << num_rows << endl;
        for (size_t i = 0; i < num_fields; ++i) {
            const soci::column_properties &props = v.get_properties(i);
            cout << props.get_name() << '\t';
        }
        cout << endl;
        do {
            stringstream ss;
            for (size_t i = 0; i < num_fields; ++i) {
                if (v.get_indicator(i) == soci::i_null) {
                    ss << "NULL";
                    break;
                }
                const soci::column_properties &props = v.get_properties(i);
                switch (props.get_data_type()) {
                case soci::dt_string:
                    ss << v.get<string>(i);
                    break;
                case soci::dt_double:
                    ss << v.get<double>(i);
                    break;
                case soci::dt_integer:
                    ss << v.get<int>(i);
                    break;
                case soci::dt_long_long:
                    ss << v.get<long long>(i);
                    break;
                case soci::dt_unsigned_long_long:
                    ss << v.get<unsigned long long>(i);
                    break;
                case soci::dt_date:
                    tm dt = v.get<tm>(i);
                    ss << asctime(&dt);
                    break;
                }
                ss << '\t';
            }
            cout << ss.str() << endl;
        } while (st.fetch());
    } catch (soci::soci_error &e) {
        cerr << "Error: " << e.what() << endl;
    }
    return 0;
}

#include "soci.h"

#include "soci-mysql.h"

//#include "soci-oracle.h"

#include <ctime>

#include <string>

#include <iostream>

#include <sstream>

using namespace std;

int main()

{

try {

soci::session sql(soci::mysql, "host=192.168.1.101 db=mysql user=root password=111111");

//soci::session sql(soci::oracle, "service=192.168.1.102/ORCL user=sys password=111111");

soci::row v;

/* comma operator is overloaded here.. */

soci::statement st = (sql.prepare << "SELECT * FROM user", into(v));

//soci::statement st = (sql.prepare << "SELECT * FROM SYS.USER$", into(v));

st.execute(true); /* with data exchange */

unsigned int num_fields = v.size();

cout << "fields: " << num_fields << endl;

num_fields = (num_fields <= 9) ? num_fields : 9;

unsigned long num_rows = (unsigned long)st.get_affected_rows();

cout << "rows: " << num_rows << endl;

for (size_t i = 0; i < num_fields; ++i) {

const soci::column_properties &props = v.get_properties(i);

cout << props.get_name() << '\t';

}

cout << endl;

do {

stringstream ss;

for (size_t i = 0; i < num_fields; ++i) {

if (v.get_indicator(i) == soci::i_null) {

ss << "NULL";

break;

}

const soci::column_properties &props = v.get_properties(i);

switch (props.get_data_type()) {

case soci::dt_string:

ss << v.get<string>(i);

break;

case soci::dt_double:

ss << v.get<double>(i);

break;

case soci::dt_integer:

ss << v.get<int>(i);

break;

case soci::dt_long_long:

ss << v.get<long long>(i);

break;

case soci::dt_unsigned_long_long:

ss << v.get<unsigned long long>(i);

break;

case soci::dt_date:

tm dt = v.get<tm>(i);

ss << asctime(&dt);

break;

}

ss << '\t';

}

cout << ss.str() << endl;

} while (st.fetch());

} catch (soci::soci_error &e) {

cerr << "Error: " << e.what() << endl;

}

return 0;

}

Updated Apr 20, 2015:

1. Under RHEL5/CentOS5, I got errors like:

./test_oracle: error while loading shared libraries: /home/gonwan/oracle11_64/lib/libnnz11.so: cannot restore segment prot after reloc: Permission denied

1	./test_oracle: error while loading shared libraries: /home/gonwan/oracle11_64/lib/libnnz11.so: cannot restore segment prot after reloc: Permission denied

It’s due to SELinux security feature. Simply workaround it with:

# chcon -t texrel_shlib_t *.so*

1	# chcon -t texrel_shlib_t .so

2. Oracle uses oraociei11.dll or libociei.so for client data. They are both large files(110+MB), since they support multiple languages. Instead, you can use oraociicus11.dll(30+MB) or libociicus.so(10-MB). These files contain only English support.

Qt4学习笔记 (7)

Posted on 2015-01-22 by gonwan — No Comments ↓

This is a repost from my previous Qt learning series, based on Qt 4.3.

本篇说一下Qt对于脚本的支持, 即QtScript模块.

    Qt支持的脚本基于ECMAScript脚本语言, 这个东西又是javascript, jscript的基础. 所以, 一般只要学过javascript就基本会写Qt脚本了. 自此开始, Qt脚本现在就叫javascript.
    不过作为土人, javascript中有一个prototype的概念, 现在才知道. javascript本没有类的概念, 跟不用说是继承之类的了. 但是凭借prototype的特性, 我们可以实现类似C++中类, 以及类继承等一些特性.
    prototype是个什么概念? 因为这个单词实在表意不清, 导致我花了很多时间来理解这个. 每个javascript对象都有一个指向另一个对象的引用, 这就是它的prototype. 一个对象的prototype定义了这个对象可以进行的操作集. 用C++来类比的话, 这些操作集是一定是成员函数. 看下面的javascript代码:

function Shape(x, y) {
    this.x = x;
    this.y = y;
}
Shape.prototype.area = function() { return 0; }

function Circle(x, y, radius) {
    Shape.call(this, x, y);
    this.radius = radius;
}
Circle.prototype = new Shape;
Circle.prototype.area = function() {
    return Math.PI * this.radius * this.radius;
}

function Shape(x, y) {

this.x = x;

this.y = y;

}

Shape.prototype.area = function() { return 0; }

function Circle(x, y, radius) {

Shape.call(this, x, y);

this.radius = radius;

}

Circle.prototype = new Shape;

Circle.prototype.area = function() {

return Math.PI * this.radius * this.radius;

}

我们把Circle对象的prototype设置成Shape对象, 实际上就是把Shape对象的prototype赋给了Circle对象, 让Circle对象的初始操作集跟Circle对象是一样的. 之后我们又重载了area()函数, 当然我们还可以加入新的函数. 它对应的C++代码如下:

class Shape
{
public:
    Shape(double x, double y) {
        this->x = x;
        this->y = y;
    }
    virtual double area() const { return 0; }
    double x;
    double y;
};

class Circle : public Shape
{
public:
    Circle(double x, double y, double radius) : Shape(x, y)
    {
        this->radius = radius;
    }
    double area() const { return M_PI * radius * radius; }
    double radius;
};

class Shape

{

public:

Shape(double x, double y) {

this->x = x;

this->y = y;

}

virtual double area() const { return 0; }

double x;

double y;

};

class Circle : public Shape

{

public:

Circle(double x, double y, double radius) : Shape(x, y)

{

this->radius = radius;

}

double area() const { return M_PI * radius * radius; }

double radius;

};

所以, 我们看到了, 对于一个javascript对象来说, 它还包括了一个内部的prototype对象. 对于Qt要用C++来实现类似prototype的功能的话, 除了要写一个javascript中的对应类, 还要写这个类对应的prototype类. 这个东西很高级, 也很麻烦, 所以建议看官方文档: http://doc.trolltech.com/4.3/qtscript.html#making-use-of-prototype-based-inheritance

下面我们来说一下一般怎样从Qt的C++代码中调用Qt的script代码. 假设我们要写一个dialog, 上面有一个QPushButton, 一个QLineEdit. 点击QPushButton的时候, 会弹出一个QMessageBox来显示消息.

a) 直接写Qt的C++代码的话, 只要用signal/slot就行了:

void HelloDialog::helloClicked()
{
    QString text = textEdit->text();
    text = "Hello " + text;
    QMessageBox::information(this, "info", text);
}

void HelloDialog::helloClicked()

{

QString text = textEdit->text();

text = "Hello " + text;

QMessageBox::information(this, "info", text);

}

b) 现在我们要加入javascript 的支持. 要解决的大概有这么一些问题: javascript中怎么拿到QLineEdit里的字符串? javascript中怎么调用QMessage这个Qt的类? 我们还是先来看代码:

QScriptValue constructQMessageBox(QScriptContext *, QScriptEngine *engine) {
    return engine->newQObject(new QMessageBox());
}

void HelloDialog::helloClicked()
{
    QString helloScript = scriptsDir.filePath("xxx.js");
    QFile file(helloScript);
    if (!file.open(QIODevice::ReadOnly)) {
        return;
    }
    QTextStream in(&file);
    in.setCodec("UTF-8");
    QString script = in.readAll();
    file.close();
    // section 1
    QScriptEngine engine;
    QScriptValue helloDialog = engine.newQObject(this);
    engine.globalObject().setProperty("helloDialog", helloDialog);
    // section 2
    QScriptValue constructor = engine.newFunction(constructQMessageBox);
    QScriptValue qsMetaObject = engine.newQMetaObject(&(QMessageBox::staticMetaObject), constructor);
    engine.globalObject().setProperty("QMessageBox", qsMetaObject);

    QScriptValue result = engine.evaluate(script);
}

QScriptValue constructQMessageBox(QScriptContext *, QScriptEngine *engine) {

return engine->newQObject(new QMessageBox());

}

void HelloDialog::helloClicked()

{

QString helloScript = scriptsDir.filePath("xxx.js");

QFile file(helloScript);

if (!file.open(QIODevice::ReadOnly)) {

return;

}

QTextStream in(&file);

in.setCodec("UTF-8");

QString script = in.readAll();

file.close();

// section 1

QScriptEngine engine;

QScriptValue helloDialog = engine.newQObject(this);

engine.globalObject().setProperty("helloDialog", helloDialog);

// section 2

QScriptValue constructor = engine.newFunction(constructQMessageBox);

QScriptValue qsMetaObject = engine.newQMetaObject(&(QMessageBox::staticMetaObject), constructor);

engine.globalObject().setProperty("QMessageBox", qsMetaObject);

QScriptValue result = engine.evaluate(script);

}

    我们先把整个javascript文件读进来, 加入一堆设置, 最后调用QScriptEngine::evaluate()函数来执行这段javascript. QScriptEngine这个类就相当于javascript的解释器.
    javascript里没有类这个概念, 所有的变量都是var类型. 如果要让Qt的C++类在javascript里运行, 那么先要将它包装(wrap)成一个javascript的类型. 代码的section 1部分把this(即当前的dialog)先做了包装, 然后把包装后的对象加入到javascript的运行环境的全局变量中.
    接着来解决QMessageBox的问题. 由于javascript中没有类, 继而也就是没构造函数这个概念, 但是当我们在javascript中new一个Qt C++对象的时候, 还是需要调用它的构造函数. 代码的section 2部分先把一个C++回调函数(之所以称为回调函数, 是因为要作为QScriptEngine::newFunction()的参数, signature是固定的)包装成一个QScriptValue, 然后把它和QMessageBox的meta-object信息一起包装成一个QScriptValue, 最后依样画葫芦地加入到javascript的运行环境的全局变量中. 这样我们就能在javascript中new出一个QMessageBox了.
    有一个很重要问题. 就是Qt的meta-object系统和javascript的调用系统是有对应关系的. 在javascript中, 一个var如果是QObject包装而来, 那么这个QObject的所有property(Q_PROPERTY声明), signal/slot都是可以在javascript中调用的. 还有就是这个QObject的所有child (指的是包含而不是继承关系), 也是可以直接访问的.
    看一下javascript代码. 其中greeting和text都是属性:

function showMessage(parent, title, text)
{
    var messageBox = new QMessageBox;
    messageBox.windowTitle = title;
    messageBox.text = text;
    messageBox.icon = QMessageBox.Information;
    return messageBox.exec();
}

return showMessage(helloDialog, "info", helloDialog.greeting + " " + helloDialog.text);

function showMessage(parent, title, text)

{

var messageBox = new QMessageBox;

messageBox.windowTitle = title;

messageBox.text = text;

messageBox.icon = QMessageBox.Information;

return messageBox.exec();

}

return showMessage(helloDialog, "info", helloDialog.greeting + " " + helloDialog.text);

c) 我们实现了用javascript来控制逻辑. GUI的话, Qt也提供了一种可以直接读取*.ui的方法: QUiLoader::load()函数. 于是我们连GUI也可以不用直接编译到binary里去了. 我们要做的就是用Qt的C++代码搭一个大概的框架, 加载需要的*.ui, *.js文件, 在适当的时候调用适当的javascript函数就行了. 而且*.ui文件对于每个控件都会有一个objectName的属性, 用uic生成代码的话, 这个值就是变量名, 如果用QUiLoader::load()的话, 这个就被赋给了QObject的objectName这个property. 当我们要在一个QWidget的javascript对象里引用它的子控件的时候, 便能直接用这个objectName来引用. 于是*.ui 和*.js文件可以说简直配合的天衣无缝那.
还是来看代码, Qt的C++代码没什么好说的, 就看javascript代码:

function showMessage(parent, title, text)
{
    var messageBox = new QMessageBox;
    messageBox.windowTitle = title;
    messageBox.text = text;
    messageBox.icon = QMessageBox.Information;
    return messageBox.exec();
}

function doClick()
{
    var text = dialog.textEdit.text;
    showMessage(dialog, "info", "Hello " + text);
}

dialog.show();
dialog.helloButton.clicked.connect(doClick);
return 0;

function showMessage(parent, title, text)

{

var messageBox = new QMessageBox;

messageBox.windowTitle = title;

messageBox.text = text;

messageBox.icon = QMessageBox.Information;

return messageBox.exec();

}

function doClick()

{

var text = dialog.textEdit.text;

showMessage(dialog, "info", "Hello " + text);

}

dialog.show();

dialog.helloButton.clicked.connect(doClick);

return 0;

直接访问子控件是不是清爽多了? 呵呵. 代码见这里. 其它请参考官方文档:
*) http://doc.trolltech.com/4.3/ecmascript.html
*) http://doc.trolltech.com/4.3/qtscript.html

Qt4学习笔记 (6)

Posted on 2015-01-22 by gonwan — No Comments ↓

This is a repost from my previous Qt learning series, based on Qt 4.3.

本篇继续介绍Qt的高级特性:

1. L&F Customization (自定义观感)

这个东西也就是传说中的skining, 换皮肤(画皮? – -). 如果你用过mfc或者java来实现控件的换肤功能的话, 那你一定觉得那是最恐怖的事情, 简直是一张张的图片往上贴啊… Qt也可以这么做, 但是提供了2种更聪明方便的方法:
a) qss (Qt Style Sheet): 这个东西灵感来源于html的css (书上也的是”inspired by”, 我就直译啦). 也就是说用qss来控制观感, 逻辑什么的还是用C++代码. 然后我就不介绍啦, 看看官方文档吧: http://doc.trolltech.com/4.3/stylesheet-syntax.html
b) 子类化QStyle类: Qt把所有观感相关的数据都抽象到了QStyle或者它的子类中, 我们要支持一个新的L&F的话, 只要继承这个类或者其子类, 重载一些函数就可以了. 这个我也不详细说啦, 书上也几乎都是抄的官方文档: http://doc.trolltech.com/4.3/style-reference.html

2. 插件框架:

    我们来想一下, 对于插件一般的实现方法. 能想到的大概是这样. 写一堆dll, 这些dll都提供统一的export接口函数.
    Qt的做法做法是差不多的, 只是在中间又提供了一层跨平台的抽象(shared dll在各个平台的实现都是不一样的嘛) 以及精简接口. 用PE Explorer可以看到所有的Qt plugin都只export了2个函数: qt_plugin_instance(), qt_plugin_query_verification_data(), 不过这两个函数具体是怎么调用的还没survey过.
    Qt的plugin可以分为两类: Qt本身的plugin和自己写的application的plugin.
    Qt的plugin可以implement 已有的接口. 比如可以implement QStylePlugin接口把style作为plugin, 可以implement QImageIOPlugin接口扩展Qt可以识别的图片格式, 等等. 这个就不说了.
    Qt的plugin还可以implement自定义的接口. 下面说一下大概的步骤:

a) 首先定义一个interface的类, 定义virtual functions, 最后调用Q_DECLARE_INTERFACE宏. 一般的interface都会提供这样的结构, 一个keys()接口说明当前plugin可以创建哪些object, 然后是一个创建object的函数(这里我写的doSomething()是同样的意思). 代码如下:

class QXxxInterface
{
public:
    virtual ~QXxxInterface() { }
    virtual QStringList keys() const = 0;
    virtual QXxx doSomething(QString key) = 0;
};
Q_DECLARE_INTERFACE(QXxxInterface, "com.ycool.gonwan.QXxxInterface/1.0")

class QXxxInterface

{

public:

virtual ~QXxxInterface() { }

virtual QStringList keys() const = 0;

virtual QXxx doSomething(QString key) = 0;

};

Q_DECLARE_INTERFACE(QXxxInterface, "com.ycool.gonwan.QXxxInterface/1.0")

b) Implement 这个interface, 以下分别是*.h文件和*.cpp文件:

// .h
class QMyXxxPlugin : public QObject, public QXxxInterface
{
    Q_OBJECT
    Q_INTERFACES(QXxxInterface)
public:
    QStringList keys() const;
    QXxx doSomething(QString key);
};[/code]
[code lang="cpp"][/code]// .cpp
Q_EXPORT_PLUGIN2(myxxxplugin, QMyXxxPlugin)

// .h

class QMyXxxPlugin : public QObject, public QXxxInterface

{

Q_OBJECT

Q_INTERFACES(QXxxInterface)

public:

QStringList keys() const;

QXxx doSomething(QString key);

};[/code]

[code lang="cpp"][/code]// .cpp

Q_EXPORT_PLUGIN2(myxxxplugin, QMyXxxPlugin)

*.h中的Q_INTERFACES宏用来告诉Qt的meta system这个类implement了哪个接口. 而*.cpp中Q_EXPORT_PLUGIN2宏是用来export dll接口的, 放在所有类成员函数之外调用就行了.

c) 调用, Qt提供了一个QPluginLoader类专门用来load插件. 依据上面现有的代码, 我们可以如下调用:

QPluginLoader loader("./plugins/myxxxplugin.dll");
if (QXxxInterface *interface = qobject_cast<QXxxInterface *>(loader.instance()))
{
    foreach (QString key, interface.keys())
    {
        interface.doSomething(key);
    }
}

QPluginLoader loader("./plugins/myxxxplugin.dll");

if (QXxxInterface *interface = qobject_cast<QXxxInterface *>(loader.instance()))

{

foreach (QString key, interface.keys())

{

interface.doSomething(key);

}

以上代码并不涉及具体的plugin的操作, 否则就不能叫做plugin了呵呵.
官方文档: http://doc.trolltech.com/4.3/plugins-howto.html

Qt4学习笔记 (5)

Posted on 2015-01-22 by gonwan — No Comments ↓

This is a repost from my previous Qt learning series, based on Qt 4.3.

本篇说一下Qt所谓的高级特性: i18n 的支持 (Internationalization).
首先明确一点, Qt对于unicode的支持是相当好的, 用来表示字符串的QString保存的是16-bit的QChar(官方文档上这么写哦), 跟java的char是一样的. 但是但是..实际上QString的内部数据一点也没有用到QChar, 大概是为了performance的考虑不吧, 附一段源码(/src/corelib/tools/qstring.h):

struct Data {
    QBasicAtomic ref;
    int alloc, size;
    ushort *data;
    ushort clean : 1;
    ushort simpletext : 1;
    ushort righttoleft : 1;
    ushort asciiCache : 1;
    ushort capacity : 1;
    ushort reserved : 11;
    ushort array[1];
};
Data *d;

struct Data {

QBasicAtomic ref;

int alloc, size;

ushort *data;

ushort clean : 1;

ushort simpletext : 1;

ushort righttoleft : 1;

ushort asciiCache : 1;

ushort capacity : 1;

ushort reserved : 11;

ushort array[1];

};

Data *d;

大概是这么个情况. 下面来说一下怎么样支持i18n.

a) 首先要做的就是把要翻译的string统统用tr()函数包起来(其实是QObject::tr()). 当然还有其它的方法, 不过这个最容易.

b) 编辑*.pro文件, 加入需要支持的语言信息. 比如我们要支持简体中文和日本语:

TRANSLATIONS  = find_zh.ts \
                find_ja.ts

1 2	TRANSLATIONS = find_zh.ts \ find_ja.ts

c) 运行lupdate来生成上面两个*.ts文件. lupdate会自动搜索需要翻译的字符串(用tr()函数包起来的作用):

# lupdate -verbose find.pro

1	# lupdate -verbose find.pro

d) 用Qt linguist来编辑生成的两个文件, 当然如果你够nb.. 可以手动编辑… 截张图:

e) 嗯.. 最好是全部都打勾了才好.. 工具栏上有检查选项, 通过了才打勾. 接着就是运行lrelease工具把*.ts文件转成binary的*.qm文件, 以便可以添加到Qt的resource文件(*.qrc) 中使用:

# lrelease -verbose find.pro

1	# lrelease -verbose find.pro

f) 新加一个*.qrc资源文件, 内容如下. 具体语法请查阅官方文档:

<RCC>
    <qresource prefix="/translations" >
        <file>find_ja.qm</file>
        <file>find_zh.qm</file>
    </qresource>
</RCC>

<RCC>

</qresource>

</RCC>

g) 然后就一切正常了:

# qmake find.pro
# nmake

1 2	# qmake find.pro # nmake

h) 代码里大概可以这样写, 就是对QApplication对象设一个translation的属性类, 注释可以用来切换语言:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QTranslator appTranslator;
    appTranslator.load("find_" + QLocale::system().name(), ":/translations");
    //appTranslator.load("find_zh.qm", ":/translations");
    //appTranslator.load("find_ja.qm", ":/translations");
    app.installTranslator(&appTranslator);
    FindDialog *dialog = new FindDialog;
    dialog->show();
    return app.exec();
}

int main(int argc, char *argv[])

{

QApplication app(argc, argv);

QTranslator appTranslator;

appTranslator.load("find_" + QLocale::system().name(), ":/translations");

//appTranslator.load("find_zh.qm", ":/translations");

//appTranslator.load("find_ja.qm", ":/translations");

app.installTranslator(&appTranslator);

FindDialog *dialog = new FindDialog;

dialog->show();

return app.exec();

}

还是截张图吧..三种语言…:

可以看到, Qt的layout又发挥作用了, 中文和日文的dialog相对长了一些.

以上. 代码见这里.