Trimming Extra Spaces

If a key or value in our configuration file has extra spaces at the beginning (leading) or end (trailing), we need a way to remove them. This process is often called "trimming".

Implementing Trim()

We can create a helper function called Trim() that takes a std::string and returns a new std::string with the leading and trailing spaces removed.

1#include <iostream>
2#include <string>
3
4std::string Trim(const std::string& Str) {
5  size_t First{Str.find_first_not_of(' ')};
6  if (First == std::string::npos) {
7    return Str;
8  }
9
10  size_t Last{Str.find_last_not_of(' ')};
11
12  return Str.substr(First, (Last - First + 1));
13}
14
15int main() {
16  std::string Test{"   WINDOW_WIDTH   "};
17  std::cout << "|" << Trim(Test) << "|";
18}

1|WINDOW_WIDTH|

Using Trim() in ProcessLine()

Now, let's see how we can use our Trim() function within the ProcessLine() function of our Config class:

1#include <iostream>
2#include <string>
3
4std::string Trim(const std::string& Str) {
5  // The following code is the same as the
6  // previous example
7  size_t First{Str.find_first_not_of(' ')};
8  if (First == std::string::npos) {
9    return Str;
10  }
11
12  size_t Last{Str.find_last_not_of(' ')};
13
14  return Str.substr(First, (Last - First + 1));
15}
16
Config Class|Show
17class Config {/*...*/};
34
35int main() {
36  Config C;
37  C.ProcessLine("   WINDOW_WIDTH   :    800   ");
38}

1Key: |WINDOW_WIDTH|
2Value: |800|

Here we apply Trim() to both the Key and Value strings after we've extracted them from the line. This ensures that any leading or trailing spaces are removed before we process or store the values.