Why does this happen?
This has little to do with the input you provided yourself but rather with the default behavior std::getline()
has. When you provided your input for the age (std::cin >> age
), you not only submitted the following characters, but also an implicit newline was appended to the stream when you typed Enter:
"10
"
A newline is always appended to your input when you select Enter or Return when submitting from a terminal. It is also used in files for moving toward the next line. The newline is left in the buffer after the extraction into age
until the next I/O operation where it is either discarded or read. When the flow of control reaches std::getline()
, it will see "
Mr. Whiskers"
and the newline at the beginning will be discarded, but the input operation will stop immediately. The reason this happens is because the job of std::getline()
is to attempt to read characters and stop when it finds a newline. So the rest of your input is left in the buffer unread.
Solution
cin.ignore()
To fix this, one option is to skip over the newline before doing std::getline()
. You can do this by calling std::cin.ignore()
after the first input operation. It will discard the next character (the newline character) so that it is no longer in the way.
std::cin >> age;
std::cin.ignore();
std::getline(std::cin, name);
Match the operations
When you run into an issue like this it's usually because you're combining formatted input operations with unformatted input operations. A formatted input operation is when you take input and format it for a certain type. That's what operator>>()
is for. Unformatted input operations are anything other than that, like std::getline()
, std::cin.read()
, std::cin.get()
, etc. Those functions don't care about the format of the input and only process raw text.
If you stick to using a single type of formatting then you can avoid this annoying issue:
// Unformatted I/O
std::string age, name;
std::getline(std::cin, age);
std::getline(std::cin, name);
or
// Formatted I/O
int age;
std::string first_name, last_name;
std::cin >> age >> first_name >> last_name;
If you choose to read everything as strings using the unformatted operations you can convert them into the appropriate types afterwards.
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