TypeScript this 关键字上下文错误 - 未定义

Question

I have a aws lambda written in JS (TypeScript) which calls functions from different classes. I am getting undefined for the existingproducts variable even though it works fine when the REACT UI sends a call to the function. Below is my code using this keyword to reference the method of other class with current object in scope.

Entry point for the lambda

export const handler = async (upload: FileUpload, context: Context) => {
     .....code .....
     const parser = new ExcelValidator(new LookupService(), new ProductService());
     const status = await parser.performExistingUpcValidation(products as Product[], upload, workbook);
     return status

PerformExisitingUPCValidation

export class ExcelValidator {

    constructor(public lookupService: LookupService, public productService: ProductService) {

    }

    async performExistingUpcValidation(products: Product[], upload: FileUpload, workbook?: Workbook): Promise<FileStatus> {
       ...code...
       const existingProducts: any[] = await this.productService.getExistingProductsByUpcOrProductCode(productUpcs, productCodes);
       console.log("This is the exisitingProduct", existingProducts)
}

ProductServiceClass

export class ProductService {


    constructor() {
    }

    @Query(()=>[Product])
    async getExistingProductsByUpcOrProductCode(@Arg("upcs", ()=> [String]) upcs: string[], @Arg("productCodes", ()=> [String]) productCodes: string[]): Promise<Product[]> {
        console.log("I came here")
        let query = `SELECT * from table
            in (${upcs.join(",")})`;
        if(productCodes.length){
            query += ` OR "productCode" in ('${productCodes.join("','")}')`;
        }
        const results = await pool.snowflake?.execute(query);
        return results as Product[];
    }

After all the execution I am able to see

This is the exisitingProduct undefined

which means my execution does not reach the ProductServiceClass. Can someone point me to what is wrong or missing? Also any documentation/reference to read more will help alot.

Answer 1

My suggestion for you is review the item below:

const results = await pool.snowflake?.execute(query);

Are you confident that snowflake is not null, because you are accepting to be undefined with help of the question mark.