how do I create an instance of a struct? | Rust Programming Language Community | Page 1

prisma remnant Mar 7, 2023, 9:07 PM

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what error are you getting?

covert dock Mar 7, 2023, 9:08 PM

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its not an error I just dont know how to use the struct and how to create an instance of them

prisma remnant Mar 7, 2023, 9:08 PM

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User { ... } is how you do it

quasi tree Mar 7, 2023, 9:09 PM

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Yeah ... that code above just does it

covert dock Mar 7, 2023, 9:09 PM

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so to set values do I just make an instance of the struct and then change the values from the original?

prisma remnant Mar 7, 2023, 9:09 PM

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covert dock so to set values do I just make an instance of the struct and then change the va...

yes, that's what your code is already doing

covert dock Mar 7, 2023, 9:10 PM

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im used to oop which is why its so confusing for me 😆

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oh shit

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i just realized I pasted in the wrong code 💀

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    name: String,
    hex: String,
}

struct ColorTupleStruct(String, String);

fn classic_c_structs() -> ColorClassicStruct {
    let green =
    return green
}

fn tuple_structs() -> ColorTupleStruct {
    let green =
    return green
}

fn main() {
    let cl_str = classic_c_structs();
    println!("{}", "Classic Struct:");
    println!("Name: {}", cl_str.name);
    println!("Hex: {}", cl_str.hex);

    let tup_str = tuple_structs();
    println!("{}", "Tuple Struct:");
    println!("Name: {}", tup_str.0);
    println!("Hex: {}", tup_str.1);
}

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theres the right code

quasi tree Mar 7, 2023, 9:12 PM

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Ah yeah this looks more like a question 😄

blazing hill Mar 7, 2023, 9:13 PM

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Well, in either case, same as your previous one

let mut foo = ColorClassicStruct {
    name: "foo".to_string(),
    hex: "#000000".to_string()
};

foo.name = "bar".to_string();

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mut allows you to set the values in it

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StructName {} to create one

covert dock Mar 7, 2023, 9:13 PM

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do I need to put it in main or each function

blazing hill Mar 7, 2023, 9:14 PM

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You need to initialize your struct inside the functions, then let it return

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The functions return an owned value (no reference to borrow from in the arguments)

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So you need to make an owned one inside the function so you can return it

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A nice simple example would be

fn foo() -> MyStruct {
    // instantiate owned MyStruct and return it
    MyStruct {
        name: "green".to_string(),
        hex: "#00FF00".to_string()
    }
}

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Note the lack of a semicolon ;. When you don't put a semicolon, it'll evaluate to that value

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; strictly speaking evaluates to Unit () (which is Rust representation for no value)

covert dock Mar 7, 2023, 9:19 PM

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thanks!

blazing hill Mar 7, 2023, 9:20 PM

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You can also use a return value; if you prefer. It does the same thing as the above

covert dock Mar 7, 2023, 9:21 PM

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yup, it worked tysm

tough tiger Mar 8, 2023, 5:26 AM

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some people use Struct::new for that constructor syntax

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struct S { x: Param }
impl {
  pub fn new (x: Param) -> Self {
    Self { x }
  }
}
S::new(x);

covert dock Mar 8, 2023, 3:14 PM

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tough tiger some people use `Struct::new` for that constructor syntax

Thanks, didn’t know that existed

left adder Mar 8, 2023, 3:21 PM

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covert dock Thanks, didn’t know that existed

note that there isnt actually a concept of constructors, its just convention to have an associated function called new that makes an instance of it, so you can do Type::new(params)

covert dock Mar 8, 2023, 3:22 PM

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that makes sense, im new to non oop so that helps

#how do I create an instance of a struct?