boost中的path::string()和path::generic_string()有什么区别？

Question

boost::path::string()和boost::path::generic_string()之间有什么区别，我应该什么时候使用它们？

Answer 1

This is clearly stated in the documentation ; you need only read the documentation to gain knowledge and understanding. Please get into the habit of doing that, starting from now.

boost::path::string

Returns a std::string in the native pathname format .

boost::path::generic_string

Returns a std::string in the generic pathname format .

When to use each of them

Well, that's up to you, and depends on your needs! The following quotation, again from the documentation, may help…

[Note: For ISO/IEC 9945, no conversion occurs, since the native format and generic format are the same. For Windows, backslashes are converted to slashes --end note]

In day-to-day use, you can effectively say:

• On Windows, native format has backslashes and generic format has slashes;
• On Linux, both formats have slashes.

Answer 2

Reading your mind, you are programming on a Windows system.

On your system, as far as boost can tell, the preferred separator between path elements is \\ . However, / is an acceptable separator.

The constructor to boost::fs::path docs state:

[Note: For ISO/IEC 9945 and Windows implementations, the generic format is already acceptable as a native format, so no generic to native conversion is performed. --end note]

Note the clause about Windows implementations -- the generic format (with / separators) is already acceptable, so no conversion is done.

Then when you invoke t/fn the appends or / or /= operator is used. It states:

[Note: For ISO/IEC 9945-like implementations, including Unix variants, Linux, and Mac OS X, the preferred directory separator is a single forward slash.

For Windows-like implementations, including Cygwin and MinGW, the preferred directory separator is a single backslash.--end note]

And the preferred separator is \\ on windows systems.

So at construction, no conversion from generic to system occurs -- but on appending with operator/ or similar, it is.

This results in your string looking ugly.

If you want to fix the problem, you could iterate over your 'malformed' path using begin and end , and store/append the elements into a new path using operator/ .

boost::fs::path fix( boost::fs::path in ) {
  boost::fs::path retval;
  for ( auto element : in ) {
    if (retval.empty())
      retval = in;
    else
      retval /= in;
  }
  return retval;
}

which if I read the docs right will take your mixed-slash path and generate a clean one.

If you are stuck in C++03 iterate over in using in.begin() and in.end() and boost::fs::path::iterator .