Small question about Tutorial App

[henk_stobbe]

Hello,

(do no worries everything works now (-;)

Small question about below,

    const formatter: FormatOptions<Unit, ConvertableUnit> = {
    maximumFractionDigits: chartPrecision,

This means we have a formatter of type FormatOptions expecting two props.

Where in the documentation can I find the FormatOptions type?

I assume this is the interface input-ToUnid and output-FromUnit but I guess this is defined in the Runtime,

Am I missing something?

KR Henk

[stefan_eggersto]

Hi again 🙂

You can find the type reference at https://developer.dynatrace.com/reference/sdks/units/#formatoptions 

The properties of FormatOptions tell the formatter how it should behave, for example, to which unit it should convert the input or if it should abbreviate the number.

[henk_stobbe]

Stefan please make my day😀

Looking at your link,

Is const formatter: FormatOptions<ToUnit, ConvertableUnit>

Not a better, or am I still missing something?

KR Henk

[stefan_eggersto · Accepted solution]

Hi @henk_stobbe ,

It took me some time to dig into that since the typing of this package is all but trivial. Long story short:

• The documentation is mixing types (e.g. ConvertableUnit) and type parameters (FromUnit and ToUnit). Only types should be documented there.
• In the tutorial, the definition of formatter needs to refer to types, so only const formatter: FormatOptions<Unit, ConvertableUnit> is valid, but not const formatter: FormatOptions<FromUnit, ToUnit>

Now the longer story with some background information 🙂 The relevant parts of the type definition of FormatOptions is following:

export interface FormatOptions<FromUnit extends Unit, ToUnit extends ConvertableUnit> {
    ...
    input?: FromUnit;
    output?: ToUnit;
    ...
}

This means:

• FormatOptions is a generic interface with two type parameters
• Unit and ConvertableUnit are types provided by the SDK. units.currency.usd satisfies the type Unit, so you can write the following valid assignment: const myUnit: Unit = units.currency.usd;
• FromUnit and ToUnit are just the names of the type parameters and only valid within this type definition
• According to this signature, FromUnit needs to be any type that extends Unit, ToUnit needs to be any type that extends ConvertableUnit

To sum it up: Unit and ConvertableUnit are relevant for consumers, ToUnit and FromUnit are just the names of the type parameters of FormatterOptions.

You can read more on generics in TypeScript at https://www.typescriptlang.org/docs/handbook/2/generics.html

[henk_stobbe]

Hello Stefan,

I realy wish I could give you more the one Kudo, great answer. Sorry for giving you the extra work.

It helped met to better understand, 

Thx! 

[radek_jasinski]

Great answer (tip) - thank you!