Rust で OpenAI API を呼ぶ例

openai.rs

use async_openai::{Client, types::{CreateCompletionRequestArgs}};

pub struct OpenAi {
    client: Client,
    model: String,
    max_tokens: u16,
}

impl OpenAi {
    pub fn new(model: String, max_tokens: u16) -> Self {
        let client = Client::new();
        Self {
            client,
            model,
            max_tokens,
        }
    }

    pub async fn ask(&self, input: &str) -> String {
        // Create request using builder pattern
        // Every request struct has companion builder struct with same name + Args suffix
        let request = CreateCompletionRequestArgs::default()
            .model(&self.model)
            .prompt(format!("以下の結果をHTMLに変換して答えてください。{}", input))
            .max_tokens(self.max_tokens)
            .build()
            .unwrap();

        // Call API
        let response = self.client.completions().create(request).await.unwrap();
        let response_text = format!("{}", response.choices.first().unwrap().text);
        response_text
    }
}

async_openai で API KEY を指定しない場合、default で環境変数に設定されている OPENAI_API_KEY という変数の値が使われます。

https://docs.rs/async-openai/latest/async_openai/

// Create a client with api key from env var OPENAI_API_KEY and default base url.
let client = Client::new();