Initialize complex structures from file input

One strength of the input stream is its ability to parse different types of data from a text file and convert them to their corresponding fundamental types. Here's a simple technique for importing data into a container of structures using an input stream.

How to do it…

In this recipe, we'll take a data file and import its disparate fields into a vector of struct objects. The data file represents cities with their populations and map coordinates:

• This is cities.txt, the data file we'll read:

  Las Vegas
  661903 36.1699 -115.1398
  New York City
  8850000 40.7128 -74.0060
  Berlin
  3571000 52.5200 13.4050
  Mexico City
  21900000 19.4326 -99.1332
  Sydney
  5312000 -33.8688 151.2093

The city name is on a line by itself. The second line is population, followed by longitude and latitude. This pattern repeats for each of the five cities.

• We'll define our filename in a constant so that we can open it later...