using_statement


Function call that acts like a
using statement.

With Deno:

``ts
import { using } from "https://deno.land/x/using_statement/mod.ts";
`

Or with Node:

`
npm install --save using-statement
`

Example

Before:

`ts
const camera = new Camera();
try {
outputPicture(camera.takePictureSync());
} finally {
camera.dispose();
}
`

After:

`ts
import { using } from "https://deno.land/x/using_statement/mod.ts";

using(new Camera(), (camera) => {
outputPicture(camera.takePictureSync());
});
`

Features

- Supports synchronous, asynchronous, and generator functions.
- Handles exceptions to ensure the resource is properly disposed.
- Accepts objects with a dispose(), close(), or unsubscribe() method.
- Allows asynchronously disposing when using a synchronous or asynchronous
function.

Examples

Setup:

`ts
// Camera.ts
export class Camera {
takePictureSync() {
// ...etc...
return pictureData;
}

async takePicture() {
// ...etc...
return pictureData;
}

dispose() {
// clean up the resource this class is holding
}
}
`

Synchronous example:

`ts
import { using } from "https://deno.land/x/using_statement/mod.ts";
import { Camera } from "./Camera.ts";

using(new Camera(), (camera) => {
const picture = camera.takePictureSync();
outputPicture(picture); // some function that outputs the picture
});

// camera is disposed here
`

Asynchronous example:

`ts
import { using } from "https://deno.land/x/using_statement/mod.ts";
import { Camera } from "./Camera.ts";

await using(new Camera(), async (camera) => {
const picture = await camera.takePicture();
outputPicture(picture);
});

// camera is disposed here
`

Generator function example:

`ts
import { using } from "https://deno.land/x/using_statement/mod.ts";
import { Camera } from "./Camera.ts";

const picturesIterator = using(new Camera(), function* (camera) {
for (let i = 0; i < 10; i++) {
yield camera.takePictureSync();
}
});

// camera is not disposed yet...

for (const picture of picturesIterator) {
outputPicture(picture);
}

// camera is now disposed
``

$3

- C#'s
using statement.
- My old gist here.
- ECMAScript using statement proposal.