Re: Setting field of struct object

[Danilo via Digitalmars-d-learn]

On Monday, 22 January 2024 at 08:35:01 UTC, Joel wrote:
I've lost interest in the video, looks like horrible syntax 
(F#).

Nonetheless, this usually used with Objects (new class/struct 
instances), like so:
```d
import std;

struct Person {
    string name, email;
    ulong age;
    auto withName(string name) { this.name=name; return this; }
    auto withEmail(string email) { this.email=email; return this; 
}
    auto withAge(ulong age) { this.age=age; return this; }
}

void main() {
    auto p = (new Person).withName("Tom")
                         .withEmail("joel...@gmail.com")
                         .withAge(44);
    writeln(p);
}
```

If you convert it to a class, add an `static opCall` for 
initialization,
and a toString() method, it's even nicer:
```d
module app;

import std;

class Person {
    private string name, email;
    private ulong age;

    auto withName(string name) { this.name=name; return this; }
    auto withEmail(string email) { this.email=email; return this; 
}
    auto withAge(ulong age) { this.age=age; return this; }

    static Person opCall() => new Person();

    override string toString() {
        return "Person{ name: "~name~", age: "~age.to!string~", 
email: "~email~" }";
    }
}

void main() {
    auto p = Person()
                 .withName("Tom")
                 .withEmail("joel...@gmail.com")
                 .withAge(44);

    writeln(p);
}
```
It's common OOP style in some frameworks.