C++ : convert string to int number

Convert string to number using stringstream  

String to Number

Also converting a string to a number via stringstream takes two steps:

1. Constructing the stream from the string
2. Reading the value into the variable

For this ( as you need to read input from the stream ) an istringstream will be used While a number can always be converted in a string, a string must be valid to be converted to a number ( eg: An attempt of converting "hello" to an integer would certainly fail ) so on this conversion, some checking must be done Here is the code example: 

string Text = "456"; // string containing the number 
int Result; //number which will contain the result 
istringstream convert(Text); // stringstream used for the conversion constructed with the contents of 'Text' 
                                           // ie: the stream will start containing the characters of 'Text' 
if ( !(convert >> Result) ) //give the value to 'Result' using the characters in the stream 
          Result = 0; //if that fails set 'Result' to 0 //'Result' now equal to 456 This conversion is even easier to reduce to a single line: 
string Text = "456"; int Number; if ( ! (istringstream(Text) >> Number) ) Number = 0; 

In the above code an object of istringstream gets constructed from 'Text' istringstream(Text) and its contents get read into the numeric variable >> Number. If that operation fails if ( !, 'Number' is set to zero Number = 0; Locales and manipulators can be used as well as with any stream