QByteArray length() count() size()的区别

以前没注意length()  count() size()这几个有什么区别，都是随意用，想到哪个就用哪个，但总是疑问到底他们有没有区别。

今天就去探个究竟，于是查qt的帮助文档，终于找到答案，三个确实没有区别，都是和size一样的！

以下均摘抄自qt帮助文档，希望可以给初学者提供帮助。

int QByteArray::length() const

Same as size().

 

int QByteArray::count() const

This is an overloaded function.

Same as size().

 

int QByteArray::size() const

Returns the number of bytes in this byte array.

The last byte in the byte array is at position size() - 1. In addition, QByteArray ensures that the byte at position size() is always '\0', so that you can use the return value of data() and constData() as arguments to functions that expect '\0'-terminated strings. If the QByteArray object was created from a raw data that didn't include the trailing null-termination character then QByteArray doesn't add it automaticall unless the deep copy is created.

Example:

  QByteArray ba("Hello");
  int n = ba.size();          // n == 5
  ba.data()[0];               // returns 'H'
  ba.data()[4];               // returns 'o'
  ba.data()[5];               // returns '\0'

See also isEmpty() and resize().

 

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