QML and C++ Integration

Integrating QML and C++ provides a variety of opportunities, including the ability to:

1. Separate the user interface code from the application logic code, by implementing the former with QML and JavaScript within QML documents, and the latter with C++

2. Use and invoke some C++ functionality from QML (for example, to invoke your application logic, use a data model implemented in C++, or call some functions in a third-party C++ library)

3. Access functionality in the Qt QML or Qt Quick C++ API (for example, to dynamically generate images using QQuickImageProvider)

4. Implement your own QML object types from C++ — whether for use within your own specific application, or for distribution to others


 source: http://doc.qt.io/qt-5/qtqml-cppintegration-overview.html

change qmake version

change qmake version 

$ export QTDIR=/qtdir/Qt/5.7/gcc_64 $ export PATH=$QTDIR/bin:$PATH $ export LD_LIBRARY_PATH=$QTDIR/lib:$LD_LIBRARY_PATH
/qtdir = installed qt path
 qmake --version

[VMware workstation] solution - disable intall vmware tools (ubuntu)

[VMware workstation] solution - disable intall vmware tools (ubuntu)

1. open terminal$sudo apt-get install open-vm-tools-desktop

2. restart vmware

C Language - extern ?

Extern
- The extern keyword declares a variable or function and specifies that it has external linkage.

C++ Shift operator(KO)

Shift operator- cout, cin 쓸때 앞이나 뒤에 붙이는 연산자
- 표준 라이브러리에 std라는 namespace에 cout이나 cin에 관련된 클래스(istream, ostream)
- C++에서는 쉬프트 연산자도 연산자 오버로딩이 가능

Shift operator overloading
-----------------------------
int main()
{
    VALUE val(2,3); 
    std::cout << val;
    return 0;
}

1. VALUE class show x and y value.

2. create val Object. after, std::cout print val .

Error : 

cout : - possible normal data type printing

         - impossible object of user type

-표준 std의 ostream 클래스에서도 쉬프트 연산에 대한 오버로딩이 정의 되어 있지 않음

따라서,  표준 라이브러리로 객체를 출력하는 일 불가능

-> Solution

overloading of member fucntion

cout is cout.operator

cout.operator<< (val)

val 객체 인자값을 받을 수 있도록 cout 객체에는 operator<< 연산자를 오버로딩 시키면 가능

class VALUE{  

private:  

    int iX;

    int iY;  

public:  

    VALUE(int x=0, int y=0):iX(x), iY(y){}  

    friend ostream& operator<<(ostream& os, const VALUE& val);  

};  

  

ostream& operator<<(ostream& os, const VALUE& val)  

{  

    os<<"["<<val.iX<<", "<<val.iY<<"]"<<endl;   

    return os;  

}  

  

int main(void)  

{  

    VALUE val(2, 3);  

    std::cout<<val;  

    return 0; 

}

member func overloading : CHANGE std::cout<<val; to operator(std::cout, VALUE); 

NO logical problem. 

How to use #ifdef to C/C++

example

int testfunc(int x, int y)

{

#ifdef  _DEBUG

      printf("x=%d, Y=%d", x,y);  // if x=1, y =2 

#endif

   return  (x * Y) ;

}

if debug mode
#define _DEBUG "DEBUG"

print x=1, Y=2

after return

if release mode,

not print

return

C/C++ Data type byte range

data type

data type  byte

unsigned long       DWORD

int                        BOOL;

unsigned char       BYTE;

unsigned short      WORD;

unsigned int          UINT;

char            1 byte -128 ~ 127

unsigned char 1 byte 0 ~ 255

int8                 1 byte -128 ~ 127

int16         2 byte -32,768 to 32,767

unsigned int 2 byte -32,768 to 32,767

(signed) short (int)        2 byte -32,768 to 32,767

unsigned short (int)         2 byte 0 ~ 65,535

int32                        4 byte -2,147,483,648 ~ 2,147,483,647

(signed) int                4 byte -2,147,483,648 ~ 2,147,483,647

unsigned int                4 byte 0 ~ 4,294,967,295

(signed) long (int)        4 byte -2,147,483,648 ~ 2,147,483,647

unsigned long (ing)          4 byte -2,147,483,648 ~ 2,147,483,647

int64                        8 byte -9,223,372,036,854,775,808 ~ 9,223,372,036,854,775,807

float                                 4 byte 3.4E +/- 38 (7 digits)

double                        8 byte 1.7E +/- 308 (15 digits)

long double                8 byte 1.2E +/- 4932 (19 digits)