如何在angular5服务中创建具有泛型类型的新实例

Question

I need to create a new instance with a generic type in angular5 service.
Check out the following codes, please.

@Injectable()
export class LookupService {
  duplicate<T>(lookup: T) {
    const temp = new T(lookup);
    return temp;
  }
}

But it's not working. I've been trying to find a solution over a day but can't find it yet.

Thanks

Answer 1

You're close the correct usage:

@Injectable()
export class LookupService {
    // You need also a reference to the class to create a new object
    duplicate<T>(lookup: T, clazz: { new(): T }) {
        const temp = new clazz();
        // Set some values of lookup to temp
        return temp;
    }
 }

Sample Class

export class SampleClass {

    constructor() {
        // Some attributes
    }

}

And somewhere in a service or in a component you would call the duplicate method like this:

const obj: SampleClass = new SampleClass();
// Call the method with the object to clone and its class
this.lookupService.duplicate(obj, SampleClass);

If you "don't know" the class of the object you can use a clone method of a library like lodash .