How to get std :: getline to tell me when it got to the end of the string stream?

Question

Assuming stringstream contains James is 4 , I can write something like getline (stream, stringjames, ' ') to get single words, but is there any way to find out that I got to the end of the line?

Bonus question! Case 1: James is 4 Case 2: James is four

If I were repeating words in a string stream and I expected to get int val from 4, but instead I got a string, what would be the best way to check this?

Answer 1

You check the return value to see if it evaluates to true or false:

 if (getline(stream, stringjames, ' ')) // do stuff else // fail 

Regarding the "bonus question", you can also do the same when fetching int and things from threads. The returned value of operator>> will be evaluated to true if the reading was successful, and false if there was an error (for example, there were letters instead of letters):

 int intval; if (stream >> intval) // int read, process else if (stream.eof()) // end-of-stream reached else // int failed to read but there is still stuff left in the stream 

Answer 2

Suppose the stringstream contains James is 4, I can write something like getline (stream, stringjames, '') to get individual words, but is there any way to find out that I got to the end of the line?

As a rule, the easiest way is to read the variable std::string - by default it is assumed that it is limited to a space:

 std::string word; while (some_stream >> word) { // first iteration "James", then "is", then "4", then breaks from while... } 

Bonus question! Case 1: James 4 Case 2: James Four

If I were repeating words in a string stream and I expected to get int val from 4, but instead I got a string, what would be the best way to check this?

It is best to first read it into a string and then check if you can convert this string to a number. You can try strtoi etc. - they help indicate whether the entire value is a legal number so that you can detect and reject the values, for example, say “4q”.

An alternative is to try to do the streaming conversion to an integral type first, and only if it fails reset the error flags in the stream and get a string instead. I can’t remember if you need to move the stream so that you can read the string variable, but you could write a couple of test cases and turn them off.

Alternatively, you can use regular expressions and subexpressions to parse your input: more useful as the expression becomes more complex.