CODEWITHSUNDEEP
c++string
lhuang
lhuang

Reputation: 58

std::getline for an ifstream, using parameter string or char *

I am using fstream to read or write into a file.

I meet a problem regarding the function ifstream::getline. When I include <string>, then I can pass string as a parameter to the function, if not, I have to pass char* as the parameter. Can someone tell me why?

According to the description of the function, as I understand it, the right parameter waited should be char*. Is the string value converted to a char* here?

Upvotes: 0

Views: 805

Answers (2)

Dietmar K&#252;hl
Dietmar K&#252;hl

Reputation: 153830

There are two versions of std::getline():

std::istream::getline(char*, char = '\n'); // member function of istream
std::getline(std::istream&, std::string&, char = '\n'); // free function in <string>

When including the definition of std::istream you obviously get the member function. However, you'll need to include <string> to get the definition of std::string which also comes with its version of std::getline().

Upvotes: 2

Radnyx
Radnyx

Reputation: 324

String type isn't converted to char*. That's why .c_str() exists. But the std::string type will accept a char* as an initializer.

The two types aren't backwards compatible. std::string's will accept char*'s but char*'s don't accept std::string's.

Upvotes: 2

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