Typescript - Pass interface literals to function parameters

Question

I want to use an interface to set the data types and then call them in the function while setting a default value if they are not passed through.

I get an error of ',' expected. after canvas in the function. Can't I call it in this way?

// Options
interface options {
    canvas?: {
        width: number;
        height: number;
        bgColor: string;
    };
    brushes?: {
        sizeSm: number;
        sizeLg: number;
    };
}

function initialize(options {canvas.width = 700, brushes.sizeSm = 20}) {
    // Do stuff
}

// Call function
initialize({
    canvas: {
        width: 820,
        height: 450,
        bgColor: '#fff'
    },
    brushes: {
        sizeSm: 10,
        sizeLg: 20
    },
});

Radim Köhler · Accepted Answer · 2016-08-16 09:20:04Z

4

This should be working

interface options {
    canvas?: {
        width: number;
        height?: number;
        bgColor?: string;
    };
    brushes?: {
        sizeSm: number;
        sizeLg?: number;
    };
}

function initialize(opts: options = {canvas : { width : 700}, brushes: {sizeSm : 20}} ) {
//function initialize(options {canvas.width = 700, brushes.sizeSm = 20}) {
    // Do stuff
}

// Call function
initialize({
    canvas: {
        width: 820,
        height: 450,
        bgColor: '#fff'
    },
    brushes: {
        sizeSm: 10,
        sizeLg: 20
    },
});

Firstly, the syntax of the options as a paramter should be adjusted to consume the interface opts: options.

Next, if we want want to have a default value, we need to properly pass it:

function initialize(opts: options = {canvas : { width : 700}, brushes: {sizeSm : 20}} ) {

And because we set only width and sizeSm .. the rest is adjusted to be optional (e.g. heigth?:number)

Play with that here

answered Aug 16, 2016 at 9:20

Radim Köhler

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2 Comments

Paul Redmond Over a year ago

Wow, this looks like what I'm after. Of course, I have to set the parameter to the interface. One thing, I've done as above and I'm getting Identifier expected for the values, e.g. {width : 700}.

Radim Köhler Over a year ago

because you've used this function initialize(options {canvas : { width : 700}... and this is wrong.. because we miss the interface as a type. we need that (as in my answer) function initialize(opts: options = {canvas : { width : 700}. the opts is variable name, the :options is type and after = we can see the default value.. hope that helps a bit ;)

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