Adding property in the defined interface of the typescript

Question

I have two interface define as below.

  interface TitleFont{
      fontFamily:string;
      fontStyle:string;
      size:string; \\ need only for the title property.
      opacity:number;
   }
  interface ChartFont{
      fontFamily:string;
      fontStyle:string;
      opacity:number;
   }

Two property in my class is of defined interface type:

 class Chart  {
     title: TitleFont;
     chartTitle: ChartFont;  
  }

Size is the extra property added in TilteFont when compared to ChartFont. Is there any way to define one interface and make use of it for both the property?

Thanks in advance

Radim Köhler · Accepted Answer · 2014-06-17 06:27:52Z

1

Would not be a solution here to use inheritance and extend TitleFont from ChartFont

interface ChartFont{
    fontFamily:string;
    fontStyle:string;
    opacity:number;
}
interface TitleFont extends ChartFont {
    size:string; \\ need only for the tilte property.
}

We still have two interfaces, but in many cases we will be able to work with just a base one (ChartFont) like this

var fontSetting1 : ChartFont = Chart.title
var fontSetting2 : ChartFont = Chart.chartTitle
...
// follows common behaviour for ChartFont interface
...

And if later needed, we can up-cast:

var titleFontSetting : TitleFont = <TitleFont>fontSetting1;

edited Jun 17, 2014 at 6:27

answered Jun 17, 2014 at 6:17

Radim Köhler

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