QTextStream

QTextStream 像是一個適配器，能支持多數據源



#include <QTextStream

>

#include <QString

>

#include <QFile

>

QTextStream

 cout(stdout, QIODevice::WriteOnly);
QTextStream

 cerr(stderr, QIODevice::WriteOnly);


int main() {
QString

 str, newstr;

QTextStream

 strbuf(&str); //使用QString做數據源


  int lucky = 7;

  float pi = 3.14;

  double e = 2.71;


  cout << "An in-memory stream" << endl;

  strbuf << "luckynumber: " << lucky << endl

	 << "pi: " << pi << endl

	 << "e: " << e << endl;


  cout << str;

QFile

 data("mydata");

  data.open(QIODevice::WriteOnly);  

QTextStream

 out(&data);  
//使用QDevice做數據源

  out << str ;   

  data.close();


  cout << "Read data from the file - watch for errors." << endl;

  if(data.open(QIODevice::ReadOnly)) { /*Make sure the file exists before 

                                         attempting to read.*/
QTextStream

 in(&data);   


    int lucky2;

    in >> newstr >> lucky2;

    if (lucky != lucky2)

      cerr << "ERROR! wrong " << newstr << lucky2  << endl;

    else

      cout << newstr << " OK" << endl;


    float pi2;

    in >> newstr >> pi2;

    if (pi2 != pi) 

      cerr << "ERROR! Wrong " << newstr << pi2 << endl;

    else

      cout << newstr << " OK" << endl;


    double e2;

    in >> newstr >> e2;

    if (e2 != e) 

      cerr << "ERROR: Wrong " << newstr << e2 <<  endl;

    else

      cout << newstr << " OK" << endl;

    data.close();   

  }


  cout << "Read from file line-by-line" << endl;

  if(data.open(QIODevice::ReadOnly)) {
QTextStream

 in(&data);   


    while (not in.atEnd()) {

      newstr = in.readLine();

      cout << newstr << endl;

    }

    data.close();

  }

  return 0;

}


評註：從上面的例子可以看出，QTextStream不負責文件的打開與創建，僅僅提供文件訪問的方法，實現了功能的獨立性

，由於它支持多數據，不區分讀寫的方向，比fstream流使用起來更加方便