QByteArray QString string char*相互转换

char *QByteArray::data()

 

Returns a pointer to the data stored in the byte array. The pointer can be used to access and modify the bytes that compose the array. The data is '\0'-terminated, i.e. the number of bytes in the returned character string is size() + 1 for the '\0' terminator.

Example:

  QByteArray ba("Hello world");

  char *data = ba.data();

  while (*data) {

      cout << "[" << *data << "]" << endl;

      ++data;

  }

The pointer remains valid as long as the byte array isn't reallocated or destroyed. For read-only access, constData() is faster because it never causes a deep copy to occur.

This function is mostly useful to pass a byte array to a function that accepts a const char *.

The following example makes a copy of the char* returned by data(), but it will corrupt the heap and cause a crash because it does not allocate a byte for the '\0' at the end:

  QString tmp = "test";

  QByteArray text = tmp.toLocal8Bit();

  char *data = new char[text.size()]; //此处有误

  strcpy(data, text.data());

  delete [] data;

This one allocates the correct amount of space:

  QString tmp = "test";

  QByteArray text = tmp.toLocal8Bit();

  char *data = new char[text.size() + 1]; //正确

  strcpy(data, text.data());

  delete [] data;

Note: A QByteArray can store any byte values including '\0's, but most functions that take char * arguments assume that the data ends at the first '\0' they encounter.

See also constData() and operator[]().

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//常用参数类型：char *字符串， QByteArray字符数组， QString字符串

1、char* -------------> QByteArray              使用构造函数 QByteArray(const char*)

char* str;
QByteArray byte(str);  //QByteArray构造函数

2、char* -------------->QString                    使用构造函数 QString(const char*)
char* str;
QString string(str);     //QString构造函数

3、QByteArray   ------>char*                       使用成员函数 QByteArray::data()
QByteArray byte;
char* str = byte.data(); //QbyteArray::data()

4、QByteArray  ------>QString                    使用构造函数 QString(const QByteArray &ba)
QByteArray byte;
QString string(byte);  //QString构造函数

5、QString  ----------> QByteArray             使用成员函数 QString::toAscii()
QString string;
QByteArray byte = string.toAscii();  //QString::toAscii

6、QString ------------>char*                       使用 qPrintable()
QString string;
char* str = qPrintable(string);

7、QString ------------->string

QString qstr;

string str = qstr.toStdString();

8、string ---------------->QString

string str;

QString qstr = QString::fromStdString(str);