Guide to transforming API Response into Custom type in Angular 5

Question

Guide to transforming API Response into Custom type in Angular 5

Describing my method to structure the API Response -

 interface MyTest {
 property2: string
 }

Incorporating Angular 5 Service Code -

getAPI(searchKey: string) {
this.productsAPIUrl = 
                  https://localhost:44331/api/SampleData/WeatherForecasts2";

return this.http.get<MyTest>(this.productsAPIUrl);
}

The Result from my API - https://localhost:44331/api/SampleData/WeatherForecasts2 is

{"property1":"Property1","property2":"Property2","property3":"Property3"}

Utilizing the Angular Service in my Component as follows -

public incrementCounter() {

this.getAutocompleteSuggestions().subscribe((data: MyTest) => {
  console.log(data);
});
}

The Query arises after calling the Angular Service, receiving the complete Response. Although I have specified 'MyTest' type with only property2, why do complete results get returned?

What steps are needed to segregate the API Response and how can it be aligned to custom model type MyTest????

Requirement limited to Property2 data. How to effectively map it???

angular typescript angular5 angular6 typescript2.0

Answer 1

Answer №1

When TypeScript is compiled into JavaScript, the types defined in TypeScript do not hold any significance during runtime.

To work around this, you can map the object received into a new object as demonstrated in this example:

import { from } from 'rxjs';
import { map } from 'rxjs/operators';

interface MyTest {
  property2: string
}

class Example {
  private getAutocompleteSuggestions() {
    return from([{"property1":"Property1","property2":"Property2","property3":"Property3"}]);
  }

  public incrementCounter() {
    this.getAutocompleteSuggestions().pipe(map(data => { return { property2: data.property2}})).subscribe((data: MyTest) => {
      console.log(data);
    });
  }
}

new Example().incrementCounter();

Answer 2

When TypeScript is compiled into JavaScript, the types defined in TypeScript do not hold any significance during runtime.

To work around this, you can map the object received into a new object as demonstrated in this example:

import { from } from 'rxjs';
import { map } from 'rxjs/operators';

interface MyTest {
  property2: string
}

class Example {
  private getAutocompleteSuggestions() {
    return from([{"property1":"Property1","property2":"Property2","property3":"Property3"}]);
  }

  public incrementCounter() {
    this.getAutocompleteSuggestions().pipe(map(data => { return { property2: data.property2}})).subscribe((data: MyTest) => {
      console.log(data);
    });
  }
}

new Example().incrementCounter();

Answer 3

Answer №2

When dealing with TypeScript, it's important to remember that there is no concept of runtime casting. Type hinting in TypeScript simply informs the compiler how to handle a given object. For example, when you have:

this.getAutocompleteSuggestions().subscribe((data: MyTest)

you are essentially telling the compiler to "interpret the subscription argument as if it were of type MyTest," even though the actual object will never be exactly of that type (just a plain object).

If you require the entity to match the exact type, you will need to manually transform it yourself using a method like pipe map.

Answer 4

When dealing with TypeScript, it's important to remember that there is no concept of runtime casting. Type hinting in TypeScript simply informs the compiler how to handle a given object. For example, when you have:

this.getAutocompleteSuggestions().subscribe((data: MyTest)

you are essentially telling the compiler to "interpret the subscription argument as if it were of type MyTest," even though the actual object will never be exactly of that type (just a plain object).

If you require the entity to match the exact type, you will need to manually transform it yourself using a method like pipe map.

Guide to transforming API Response into Custom type in Angular 5

Answer №1

Answer №2

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