I have the following expression:
public mySentences:Array<string> = [
{id: 1, text: 'Sentence 1'},
{id: 2, text: 'Sentence 2'},
{id: 3, text: 'Sentence 3'},
{id: 4, text: 'Sentenc4 '},
];
which is not working because my array is not of type string rather contains a list of objects. How I can delcare my array to contain a list of objects?
*without a new component which declaring the a class for sentence which seem a waste
I assume you're using typescript.
To be extra cautious you can define your type as an array of objects that need to match certain interface:
type MyArrayType = Array<{id: number, text: string}>;
const arr: MyArrayType = [
{id: 1, text: 'Sentence 1'},
{id: 2, text: 'Sentence 2'},
{id: 3, text: 'Sentence 3'},
{id: 4, text: 'Sentenc4 '},
];
Or short syntax without defining a custom type:
const arr: Array<{id: number, text: string}> = [...];
public mySentences:Array<Object> = [
{id: 1, text: 'Sentence 1'},
{id: 2, text: 'Sentence 2'},
{id: 3, text: 'Sentence 3'},
{id: 4, text: 'Sentenc4 '},
];
Or rather,
export interface type{
id:number;
text:string;
}
public mySentences:type[] = [
{id: 1, text: 'Sentence 1'},
{id: 2, text: 'Sentence 2'},
{id: 3, text: 'Sentence 3'},
{id: 4, text: 'Sentenc4 '},
];
this.mySentenses.push(res). I'm getting error. Argument of type 'type[]' is not assignable to parameter of type 'type'....Another approach that is especially useful if you want to store data coming from an external API or a DB would be this:
Create a class that represent your data model
export class Data{
private id:number;
private text: string;
constructor(id,text) {
this.id = id;
this.text = text;
}
In your component class you create an empty array of type Data and populate this array whenever you get a response from API or whatever data source you are using
export class AppComponent {
private search_key: string;
private dataList: Data[] = [];
getWikiData() {
this.httpService.getDataFromAPI()
.subscribe(data => {
this.parseData(data);
});
}
parseData(jsonData: string) {
//considering you get your data in json arrays
for (let i = 0; i < jsonData[1].length; i++) {
const data = new WikiData(jsonData[1][i], jsonData[2][i]);
this.wikiData.push(data);
}
}
}
dataList to a size of 5?First, generate an Interface
Assuming you are using TypeScript & Angular CLI, you can generate one by using the following command
ng g interface car
After that set the data types of its properties
// car.interface.ts
export interface car {
id: number;
eco: boolean;
wheels: number;
name: string;
}
You can now import your interface in the class that you want.
import {car} from "app/interfaces/car.interface";
And update the collection/array of car objects by pushing items in the array.
this.car.push({
id: 12345,
eco: true,
wheels: 4,
name: 'Tesla Model S',
});
More on interfaces:
An interface is a TypeScript artifact, it is not part of ECMAScript. An interface is a way to define a contract on a function with respect to the arguments and their type. Along with functions, an interface can also be used with a Class as well to define custom types. An interface is an abstract type, it does not contain any code as a class does. It only defines the 'signature' or shape of an API. During transpilation, an interface will not generate any code, it is only used by Typescript for type checking during development. - https://angular-2-training-book.rangle.io/handout/features/interfaces.html
public mySentences:Array<any> = [
{id: 1, text: 'Sentence 1'},
{id: 2, text: 'Sentence 2'},
{id: 3, text: 'Sentence 3'},
{id: 4, text: 'Sentenc4 '},
];
OR
public mySentences:Array<object> = [
{id: 1, text: 'Sentence 1'},
{id: 2, text: 'Sentence 2'},
{id: 3, text: 'Sentence 3'},
{id: 4, text: 'Sentenc4 '},
];
Datatype: array_name:datatype[]=[];
Example string: users:string[]=[];
For array of objects:
Objecttype: object_name:objecttype[]=[{}];
Example user: Users:user[]=[{}];
And if in some cases it's coming undefined in binding, make sure to initialize it on Oninit().
type NumberArray = Array<{id: number, text: string}>;
const arr: NumberArray = [
{id: 0, text: 'Number 0'},
{id: 1, text: 'Number 1'},
{id: 2, text: 'Number 2'},
{id: 3, text: 'Number 3 '},
{id: 4, text: 'Number 4 '},
{id: 5, text: 'Number 5 '},
];
