How to do it...

1. In the src/bin folder, create a file called constructor.rs

2. Add the following code and run it with cargo run --bin constructor:

1  fn main() {
2    // We don't need to care about
3    // the internal structure of NameLength
4    // Instead, we can just call it's constructor
5    let name_length = NameLength::new("John");
6 
7    // Prints "The name 'John' is '4' characters long"
8    name_length.print();
9  }
10 
11  struct NameLength {
12    name: String,
13    length: usize,
14  }
15 
16  impl NameLength {
17    // The user doesn't need to setup length
18    // We do it for him!
19    fn new(name: &str) -> Self {
20      NameLength {
21        length: name.len(),
22        name,
23      }
24    }
25 
26    fn print(&self) {
27      println!(
28        "The name '{}' is '{}' characters long",
29          self.name,
30          self.length
31      );
32    }
33  }