Bit of a TypeScript newbie here w a question on changes nece Pulumi Community #typescript

Bit of a TypeScript newbie here w/ a question on c...

salmon-account-74572

06/22/2020, 8:35 PM

Bit of a TypeScript newbie here w/ a question on changes necessary to account for "Remove synchronous invokes" in Pulumi 2.x (described at https://www.pulumi.com/docs/get-started/install/migrating-2.0/). I was using

aws.getAvailabilityZones

and using the results to a) create an array of strings to capture the AZ names and b) use the

length

function on said array of strings to determine how many AZs were in the region. I thought that wrapping the

aws.getAvailabilityZones

pulumi.output

and then using

apply

would get me back to working, but it appears not. Code is threaded below.

salmon-account-74572

06/22/2020, 8:36 PM

Here's the original TypeScript code I was using with Pulumi 1.x:

Copy code

const rawAzInfo = aws.getAvailabilityZones({
    state: "available",
});
let azNames: Array<string> = rawAzInfo.names;
let numberOfAZs: number = azNames.length;

salmon-account-74572

06/22/2020, 8:38 PM

Here's what I was trying to use w/ Pulumi 2.x:

Copy code

const rawAzInfo = pulumi.output(aws.getAvailabilityZones({
    state: "available",
}));
let azNames = rawAzInfo.apply(rawAzInfo => rawAzInfo.names);
let numberOfAZs = azNames.length;

TS complains that I can't define

azNames

Array<string>

because of type mismatch. If I remove the type definition, then I can't define

numberOfAZs

as a

number

due to type mismatch, and then that breaks some numerical operations later in the code.

salmon-account-74572

06/22/2020, 8:39 PM

As a relative newcomer to TypeScript, I'm a bit lost on how I can resolve this. Suggestions?

faint-table-42725

06/22/2020, 8:54 PM

Since you’ll end up using the number later on, I would treat it as a promise (instead of wrapping in output). Then, either write your code w/in the

then

of the promise or use https://www.pulumi.com/docs/intro/languages/javascript/#entrypoint to use top-level

await

salmon-account-74572

06/22/2020, 9:11 PM

Thanks. Can you suggest some reading that might help me better understand working with promises? I've tried a couple variations of using

then

to no avail, so I think I need to spend some time understanding the concepts a bit better.

faint-table-42725

06/22/2020, 10:02 PM

I don’t have a “go to” resource for that. I’ve heard good things about https://www.executeprogram.com/ — and their concurrency lesson seems to be among the free lessons you can try.

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