If you're trying to use a method ofa in the global scope, that's doomed to failure. You can only call methods within functions.

If all you want is a char array with "45317" in it then just use:

char *b = "45317";

If you want to convert a string that is built at runtime into a char array, then your current method is correct - you just have to do it in the right place.

There's a built in conversion which will return the underlying string-contents as a NULL terminated character array:

 String foo = "Steve was here" char *text = foo.c_str();

That is probably all you need, unless you do want to copy into a buffer. In that case you can use the standard C library to do that:

 // Declare a buffer char buf[100]; // Copy this string into it String foo = "This is my string" snprintf( buf, sizeof(buf)-1, "%s", foo.c_str() ); // Ensure we're terminated buf[sizeof(buf)] = '\0';

(You might preferstrcpy,memcpy, etc tosnprintf.)

• 1
  1)c_str() is no replacement fortoCharArray(): your first example fails to compile with “error: invalid conversion from ‘const char*’ to ‘char*’”. Of course, if you only need aconst char *, thenc_str() is to be preferred. 2) In terms of code size,snprintf() is a very inefficient way of copying a string. 3) No need to subtract one fromsizeof(buf) in the second argument tosnprintf().

  Edgar Bonet

  – Edgar Bonet

  2017-03-20 18:46:08 +00:00

  CommentedMar 20, 2017 at 18:46

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