TypeScript中如何在new实例时填充对象？接口初始化报错求助

Let's break down your questions one by one—both are common TypeScript pitfalls around object initialization and generic class instantiation:

First off, your current syntax has two clear issues:

• You’re using new with translateObj, but translateObj is a variable typed as ITranslate—interfaces aren’t classes, so you don’t need the new keyword to create objects that match their structure.
• The chained assignment let obj = new translateObj = { ... } is invalid here; it doesn’t make logical sense to assign an object literal to translateObj and then pass that result to obj in one line like this.

Correct way to initialize an ITranslate object #

Since ITranslate is an interface (a TypeScript type constraint), you just need to create an object that matches its structure and assign it directly to your variable:

// First, confirm your interface is defined (I'll assume this exists):
interface ITranslate {
  keyTranslate: string;
  outName: string;
}

// Initialize the object correctly
let translateObj: ITranslate = {
  keyTranslate: 'subjectId',
  outName: 'name'
};

This works because TypeScript only checks that the object literal has all the required properties from the ITranslate interface—no constructor or new keyword is needed here.

Your generic class has a constructor that takes a required key parameter and an optional translate parameter of type ITranslate. Here’s how to create instances properly:

Quick context (for clarity) #

I’ll assume your IMapperServiceArray<T> interface looks something like this (since you didn’t share the full definition):

interface IMapperServiceArray<T> {
  key: string | number;
  translate?: ITranslate;
  // Add any methods your interface requires, e.g.:
  mapArray(data: T[]): any[];
}

Case 1: Create an instance without the translate parameter #

You can omit the optional translate argument entirely. Just make sure to specify the generic type T (or let TypeScript infer it automatically):

// Example: Let's say T is a `User` type you've defined
interface User {
  id: number;
  fullName: string;
}

// Explicitly specify T when instantiating
const userMapper = new MapperServiceArray<User>('userId');

Case 2: Create an instance with the translate parameter #

Use the properly initialized translateObj we created earlier, or pass an inline object that matches the ITranslate structure:

// Using the pre-defined translateObj
const userMapperWithTranslate = new MapperServiceArray<User>('userId', translateObj);

// Or passing an inline object literal (no need for a separate variable)
const userMapperWithInlineTranslate = new MapperServiceArray<User>('userId', {
  keyTranslate: 'subjectId',
  outName: 'name'
});

Bonus: Let TypeScript infer the generic type #

If you later use methods on the MapperServiceArray instance that work with T-typed data, TypeScript can often infer T automatically, so you don’t have to specify it explicitly:

// TS will infer T as User when we call mapArray with a User[]
const autoInferMapper = new MapperServiceArray('userId');
autoInferMapper.mapArray([{ id: 1, fullName: 'Alice' }]);

内容的提问来源于stack exchange，提问作者dooglu