我如何让 typescript 根据 function2E977777777777777777777777777777777777777777777777777777777777777777777777777777777777BED18 的返回类型 functionC17A94F14Z 的返回类型来推断 function 的返回类型

Question

So this function is supposed to take in an array of objects that satisfy the interface TransactionActionModel . which means they must all have a function called "save" that receives arguments of the interface SaveOptions .

Currently the return type for this saveUsingTransaction function is Promise<any[]> .

interface TransactionActionModel {
  save: ({ session }: SaveOptions) => any;
}


const saveUsingTransaction = async (
    newEntities: TransactionActionModel[]
  ) => {
    const returnsArray = [];
    // Create Transaction
    const session = mongoDBWrapper.client.startSession();
    try {
      // Start Transaction
      session.startTransaction({});

      for (const entity of newEntities) {
        const resolve = await entity.save({ session });
        returnsArray.push(resolve);
      }

      // End Transaction
      await session.commitTransaction();

      return returnsArray;
    } catch (error) {
      await session.abortTransaction();

      throw error;
    } finally {
      await session.endSession();
    }
  };

Is there any way to get the return type of the saveUsingTransaction to match the return type of the save function on the entities I pass into the saveUsingTransaction .

For Example

const person = {
 phone: "0233224444",
 save: ({session}):Person => {
      return this
     }
}

const cat = {
 weight: "30kg",
 save: ({session}): Animal => {
      return this
     }
}

const results = saveUsingTransaction([person, cat])

the type on the results variable should be ==> "[Person, Animal]"

Answer 1

Your interface should be generic:

interface TransactionActionModel<T> {
  save: ({ session }: SaveOptions) => T;
}

As well as your function:

const saveUsingTransaction = async <A extends TransactionActionModel<any>[]>(
  newEntities: [...A]
): { [K in keyof A]: ReturnType<A[K]["save"]> } => {

Use [...A] to infer A as a tuple, then use that tuple in the return type by mapping over its elements and changing them to the return type of their save function. TypeScript will infer the generic in the interface in [...A] .

Simplified demo