Extracting data elegantly from a string in C++?

Question

I may have the following inputs:

  <Object::1 <1,2><3,4><3,3>>          
  <Object::2 <1,2><3,4>>
  <Object::3 <1,2> 5>

I need two extract the value after :: (may be a string), and then the i number of values after in the <>.

So for the first example, I'd want to get:

1 <1,2> <3,4> <3,3>

I can read from the string, I'm just not sure how to get what I want from it?

Answer 1

我认为这应该对您有用(?<=::)([^<]+)\\s+.*?(<.*)> 演示

Answer 2

Hmmm, let's first read the input line into a string.

std::string text_from_file;  
getline(my_text_file, text_from_file);

You want to "skip" past the text " This involves using the find method of std::string .

std::string::size_type position_in_string;
position_in_string = text_from_file.find("<Object::");

Next, test the position. After all, we don't want to continue if the key string wasn't found.

if (position_in_string != std::string::npos)
{

The next tricky part is to get the number following the "::".
This can be done many ways, we'll try std::istringstream . We need to get the text out of the string after the "::", which is called a substring , abbreviated as substr .

unsigned int quantity = 0;
std::istringstream string_input(text_from_file.substr(position_in_string));

We can use the stream extraction operators on the text string:

string_input >> quantity;

Getting the remaining text from the input text is called parsing. Very similar to the operations above. You give it a try.

There are many posts in StackOverflow that can be very helpful. Find them by searching for "[C++] parsing read from file".