How can I set a superior class in TypeScript when collecting various different objects in one array that inherit from the same class so that TypeScript doesn't show an error?
I'm trying it like this:
interface IVehicle{
modelName: string
}
interface ICar extends IVehicle{
numberOfDoors: number,
isDropTop: boolean
}
interface IBike extends IVehicle{
hasDynamo: boolean
}
var vehicles: IVehicle[] =
[
{
modelName: "carModelName", // Error
numberOfDoors: 4,
isDropTop: true
},
{
modelName: "bikeModelName",
hasDynamo: true
}
]
Doing it this way, I'm getting errors.
I'm just able to add objects of the superior interface IVehicle
if I don't want any errors shown.
After fixing the syntax errors, you can specify the type of each individual entry in the array.
interface IVehicle {
modelName: string
}
interface ICar extends IVehicle {
numberOfDoors: number,
isDropTop: boolean
}
interface IBike extends IVehicle {
hasDynamo: boolean
}
let vehicles: IVehicle[] =
[
{
modelName: "carModelName",
numberOfDoors: 4,
isDropTop: true,
} as ICar,
{
modelName: "bikeModelName",
hasDynamo: true
} as IBike
]
Or just change the type of the array to an array of vehicle, car or bike like this:
let vehicles: Array<IVehicle | ICar | IBike> =
[
{
modelName: "carModelName",
numberOfDoors: 4,
isDropTop: true,
},
{
modelName: "bikeModelName",
hasDynamo: true
}
]
If later you want to determine if an IVehicle is IBike or ICar you can use user defined type guards to do it.
function isBike(vehicle: IVehicle): vehicle is IBike {
return (<IBike>vehicle).hasDynamo !== undefined;
}
function isCar(vehicle: IVehicle): vehicle is ICar {
return (<ICar>vehicle).numberOfDoors !== undefined;
}
function log(vehicle: IVehicle) {
if (isBike(vehicle)) {
// tsc knows vehicle is IBike
console.log(vehicle.hasDynamo);
} else if (isCar(vehicle)) {
// tsc knows vehicle is ICar
console.log(vehicle.numberOfDoors);
} else {
console.log(vehicle.modelName);
}
}
You can read more about them in the Advanced types section of the handbook.
You can also find a working example of the entire code in the playground here .
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.