How to pass variable from one method to another in impl (in Rust)

Question

Specific Question

I need to pass csv variable from load_csv function to operations function.

Code

use polars::{
    prelude::{CsvReader, SerReader},
    frame::DataFrame,
    error::PolarsResult
};

struct Boilerplate {}

impl Boilerplate {
    fn load_csv(&self) -> PolarsResult<DataFrame> {
        
        let csv = CsvReader::from_path("microsoft stock data.csv")?
        .has_header(true)
        .finish();

        // println!("{:?}", csv);

        csv
    }

    fn operations() {

    }
}

fn main() {
    let boilercode = Boilerplate{};
    println!("{:?}", boilercode.load_csv());
}

What I've tried (But, Didn't Work)

1. Declared csv variable inside main function, then tried to access it in impl.

Answer 1

You can do something like this, storing your csv in the instance of your Boilerplate.

struct Boilerplate {
    csv: PolarsResult<DataFrame>
}

impl Boilerplate {
    fn new() -> Boilerplate {
        Boilerplate {
            csv: CsvReader::from_path("microsoft stock data.csv")?
                   .has_header(true)
                   .finish();
    }

    fn operations(&self) {
        // work with self.csv
    }
}

fn main() {
    let boilercode = Boilerplate::new()
    println!("{:?}", boilercode.csv);

    boilercode.operations()
}

It's a little different then your current implementation, but I find this to be cleaner. And it also gives you the freedom to call your impl methods from others while keeping csv data in the instance. Like this:

impl Boilerplate {
    // --snip--
    fn process(&self) {
        self.operations()
    }

    fn operations(&self) {
        // work with self.csv
    }
}