How do you clear a stringstream variable

Question

I ve tried several things already   std  stringstream m  m empty    m clear      both of which don t work

User · Answer

These do not discard the data in the stringstream in gnu c        m str          m str             m str std  string       The following does empty the stringstream for me       m str   clear

User · Answer

I am always scoping it         std  stringstream ss      ss  lt  lt   what            std  stringstream ss      ss  lt  lt   the            std  stringstream ss      ss  lt  lt   heck

User · Answer

For all the standard library types the member function empty   is a query  not a command  i e  it means  are you empty   not  please throw away your contents    The clear   member function is inherited from ios and is used to clear the error state of the stream  e g  if a file stream has the error state set to eofbit  end-of-file   then calling clear   will set the error state back to goodbit  no error    For clearing the contents of a stringstream  using   m str        is correct  although using   m str std  string       is technically more efficient  because you avoid invoking the std  string constructor that takes const char   But any compiler these days should be able to generate the same code in both cases - so I would just go with whatever is more readable

User · Answer

This should be the most reliable way regardless of the compiler   m std  stringstream

User · Answer

m str        seems to work

User · Answer

You can clear the error state and empty the stringstream all in one line  std  stringstream   swap m      swap m with a default constructed stringstream   This effectively resets m to a default constructed state

User · Answer

my 2 cents   this seemed to work for me in xcode and dev-c    I had a program in the form of a menu that if executed iteratively as per the request of a user will fill up a stringstream variable which would work ok the first time the code would run but would not clear the stringstream the next time the user will run the same code  but the two lines of code below finally cleared up the stringstream variable everytime before filling up the string variable   2 hours of trial and error and google searches   btw  using each line on their own would not do the trick     clear the stringstream variable  sstm str      sstm clear       fill up the streamstream variable sstm  lt  lt   crap   lt  lt   morecrap

User · Answer

It s a conceptual problem   Stringstream is a stream  so its iterators are forward  cannot return  In an output stringstream  you need a flush   to reinitialize it  as in any other output stream

[c++] How do you clear a stringstream variable?

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