Implementing asynchronous function execution in Typescript

Question

Implementing asynchronous function execution in Typescript

I'm looking to implement asynchronous functionality in my function, but I'm uncertain on the best approach:

checkLocation() {
        return __awaiter(this, void 0, Promise, function* () {
            while (true) {
                setTimeout(function () {
                    this.diagnostic.isLocationEnabled().then(
                        (isAvailable) => {
                            console.log('Is available? ' + isAvailable);
                            if (!isAvailable) {
                                alert('Please turn on the location service');
                            }
                        }).catch((e) => {
                            console.log(e);
                        });
                }, 5000)
            }
        });
    }
}

An issue that has arisen is TS not recognizing the name __awaiter. I've attempted to follow guidelines from this source

typescript asynchronous ionic-framework

Answer 1

Answer №1

In response to your comments, the __awaiter function is not something that you manually write. It is generated by the TypeScript compiler when using async/await functions.

Regarding what you mentioned wanting to do:

[It] should check if the location service (on the phone) is enabled asynchronously

The check will always be asynchronous because

this.diagnostic.isLocationEnabled

is an asynchronous operation.

To implement the checkLocation function using async/await, you would define it as an async method and use await to consume the promise from isLocationEnabled:

async checkLocation() {
    const isAvailable = await this.diagnostic.isLocationEnabled();
    console.log('Is available? ' + isAvailable);
    if (!isAvailable) {
        alert('Please turn on the location service');
    }
    return isAvailable;
}

If you prefer to handle promises explicitly without async/await, here is the non-async/await version:

checkLocation() {
    return this.diagnostic.isLocationEnabled().then(isAvailable => {
        console.log('Is available? ' + isAvailable);
        if (!isAvailable) {
            alert('Please turn on the location service');
        }
        return isAvailable;
    });
}

I've omitted the catch handler in the examples above since error handling is deferred to the caller when returning the promise.

If checkLocation is intended to be a fire-and-forget action rather than returning the flag or its promise, you can structure it like this without using an async function and keeping the catch to handle errors:

checkLocation() {
    this.diagnostic.isLocationEnabled().then(isAvailable => {
        console.log('Is available? ' + isAvailable);
        if (!isAvailable) {
            alert('Please turn on the location service');
        }
    }).catch((e) => {
        console.log(e);
    });
}

Answer 2

In response to your comments, the __awaiter function is not something that you manually write. It is generated by the TypeScript compiler when using async/await functions.

Regarding what you mentioned wanting to do:

[It] should check if the location service (on the phone) is enabled asynchronously

The check will always be asynchronous because

this.diagnostic.isLocationEnabled

is an asynchronous operation.

To implement the checkLocation function using async/await, you would define it as an async method and use await to consume the promise from isLocationEnabled:

async checkLocation() {
    const isAvailable = await this.diagnostic.isLocationEnabled();
    console.log('Is available? ' + isAvailable);
    if (!isAvailable) {
        alert('Please turn on the location service');
    }
    return isAvailable;
}

If you prefer to handle promises explicitly without async/await, here is the non-async/await version:

checkLocation() {
    return this.diagnostic.isLocationEnabled().then(isAvailable => {
        console.log('Is available? ' + isAvailable);
        if (!isAvailable) {
            alert('Please turn on the location service');
        }
        return isAvailable;
    });
}

I've omitted the catch handler in the examples above since error handling is deferred to the caller when returning the promise.

If checkLocation is intended to be a fire-and-forget action rather than returning the flag or its promise, you can structure it like this without using an async function and keeping the catch to handle errors:

checkLocation() {
    this.diagnostic.isLocationEnabled().then(isAvailable => {
        console.log('Is available? ' + isAvailable);
        if (!isAvailable) {
            alert('Please turn on the location service');
        }
    }).catch((e) => {
        console.log(e);
    });
}

Implementing asynchronous function execution in Typescript

Answer №1

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