C Pass A String

Question

Quick probably obvious question   If I have   void print string input      cout  lt  lt  input  lt  lt  endl      How do I call it like so   print  Yo       It complains that I m passing in char    instead of std  string  Is there a way to typecast it  in the call  Instead of   string send    Yo    print send     Thanks

User · Answer

Not very technical answer but just letting you know  For easy stuff like printing you can define a sort of function in your preprocessors like  define print x  cout  lt  lt  x  lt  lt  endl

User · Answer

print string   Yo        You need to make a  temporary  std  string object out of it

User · Answer

You should be able to call print  yo    since there is a constructor for std  string which takes a const char    These single argument constructors define implicit conversions from their aguments to their class type  unless the constructor is declared explicit which is not the case for std  string    Have you actually tried to compile this code   void print std  string input        cout  lt  lt  input  lt  lt  endl     int main         print  yo       It compiles fine for me in GCC   However  if you declared print like this void print std  string amp  input  then it would fail to compile since you can t bind a non-const reference to a temporary  the string would be a temporary constructed from  yo

User · Answer

Just cast it as a const char     print  const char    Yo    will work fine

User · Answer

Well  std  string is a class  const char   is a pointer  Those are two different things  It s easy to get from string to a pointer  since it typically contains one that it can just return   but for the other way  you need to create an object of type std  string   My recommendation  Functions that take constant strings and don t modify them should always take const char   as an argument  That way  they will always work - with string literals as well as with std  string  via an implicit c str

User · Answer

The obvious way would be to call the function like this  print string  Yo

User · Answer

You can write your function to take a const std  string amp    void print const std  string amp  input        cout  lt  lt  input  lt  lt  endl      or a const char    void print const char  input        cout  lt  lt  input  lt  lt  endl      Both ways allow you to call it like this   print  Hello World  n       A temporary is made std  string someString         print someString      No temporary is made   The second version does require c str   to be called for std  strings   print  Hello World  n       No temporary is made std  string someString         print someString c str        No temporary is made

User · Answer

Make it so that your function accepts a const std  string amp  instead of by-value  Not only does this avoid the copy and is therefore always preferable when accepting strings into functions  but it also enables the compiler to construct a temporary std  string from the char   that you re giving it

[c++] C++ Pass A String

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